## Sedra Microelectronic Circuits 6th c2010 txtbk .pdf

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**Sedra Microelectronic Circuits 6th c2010 txtbk.pdf**
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Brief Contents

Part I. Devices and Basic Circuits

1. Signals and Amplifiers

2. Operational Amplifiers

3. Semiconductors

4. Diodes

5. MOS Field-Effect Transistors (MOSFETs)

6. Bipolar Junction Transistors (BJTs)

Part II. Integrated-Circuit Amplifiers

7. Building Blocks of Integrated-Circuit Amplifiers

8. Differential and Multistage Amplifiers

9. Frequency Response

10. Feedback

11. Output Stages and Power Amplifiers

12. Operational Amplifier Circuits

Part III. Digital Integrated Circuits

13. CMOS Digital Logic Circuits

14. Advanced MOS and Bipolar Logic Circuits

15. Memory Circuits

Part IV. Filters and Oscillators

16. Filters and Tuned Amplifiers

17. Signal Generators and Waveform-Shaping Circuits

http://www.oup.com/us/companion.websites/9780195323030/student/

CONTENTS

http://www.oup.com/us/companion.websites/9780195323030/student

/

Part I. Devices and Basic Circuits

Chapter 1. Signals and Amplifiers

Introduction

1.1 Signals

1.2 Frequency Spectrum of Signals

1.3 Analog and Digital Signals

1.4 Amplifiers

1.4.1 Signal Amplification

1.4.2 Amplifier Circuit Symbol

1.4.3 Voltage Gain

1.4.4 Power Gain and Current Gain

1.4.5 Expressing Gain in Decibels

1.4.6 Amplifier Power Supplies

1.4.7 Amplifier Saturation

1.4.8 Symbol Convention

1.5 Circuit Models for Amplifiers

1.5.1 Voltage Amplifiers

1.5.2 Cascaded Amplifiers

1.5.3 Other Amplifier Types

1.5.4 Relationships Between the Four Amplifier Models

1.5.5 Determining Ri and Ro

1.5.6 Unilateral Models

1.6 Frequency Response of Amplifiers

1.6.1 Measuring the Amplifier Frequency Response

1.6.2 Amplifier Bandwidth

1.6.3 Evaluating the Frequency Response of Amplifiers

1.6.4 Single-Time-Constant Networks

1.6.5 Classification of Amplifiers Based on Frequency Response

Summary

Problems

Chapter 2. Operational Amplifiers (Op Amps)

Introduction

2.1 The Ideal Op Amp

2.1.1 The Op-Amp Terminals

2.1.2 Function and Characteristics of the Ideal Op Amp

2.1.3 Differential and Common-Mode Signals

2.2 The Inverting Configuration

2.2.1 The Closed-Loop Gain

2.2.2 Effect of the Finite Open-Loop Gain

2.2.3 Input and Output Resistances

2.2.4 An Important Application: The Weighted Summer

2.3 The Noninverting Configuration

2.3.1 The Closed-Loop Gain

2.3.2 Effect of the Finite Open-Loop Gain

2.3.3 Input and Output Resistances

2.3.4 The Voltage Follower

2.4 Difference Amplifiers

2.4.1 A Single Op-Amp Difference Amplifier

2.4.2 A Superior Circuit: The Instrumentation Amplifier

2.5 Integrators and Differentiators

2.5.1 The Inverting Configuration with General Impedances

2.5.2 The Inverting Integrator

2.5.3 The Op-Amp Differentiator

2.6 DC Imperfections

2.6.1 Offset Voltage

2.6.2 Input Bias and Offset Currents

2.6.3 Effect of Vos and Ios on the Operation of the Inverting Integrator

2.7 Effect of Finite Open-Loop Gain and Bandwidth on Circuit Performance

2.7.1 Frequency Dependence of the Open-Loop Gain

2.7.2 Frequency Response of the Closed-Loop Amplifier

2.8 Large-Signal Operation of Op Amps

2.8.1 Output Voltage Saturation

2.8.2 Output Current Limits

2.8.3 Slew Rate

2.8.4 Full-Power Bandwidth

Summary

Problems

Chapter 3. Semiconductors

3.1 Intrinsic Semiconductors

3.2 Doped Semiconductors

3.3 Current Flow in Semiconductors

3.3.1 Drift Current

3.3.2 Diffusion Current

3.3.3 Relationship Between D and ?

3.4 The pn Junction with Open-Circuit Terminals (Equilibrium)

3.4.1 Physical Structure

3.4.2 Operation with Open-Circuit Terminals

3.5 The pn Junction with Applied Voltage

3.5.1 Qualitative Description of Junction Operation

3.5.2 The Current-Voltage Relationship of the Junction

3.5.3 Reverse Breakdown

3.6 Capacitive Effects in the pn Junction

3.6.1 Depletion or Junction Capacitance

3.6.2 Diffusion Capacitance

Summary

Problems

Chapter 4. Diodes

4.1 The Ideal Diode

4.1.1 Current-Voltage Characteristic

4.1.2 A Simple Application: The Rectifier

4.1.3 Another Application: Diode Logic Gates

4.2 Terminal Characteristics of Junction Diodes

4.2.1 The Forward-Bias Region

4.2.2 The Reverse-Bias Region

4.2.3 The Breakdown Region

4.3 Modelling the Diode Forward Characteristic

4.3.1 The Exponential Model

4.3.2 Graphical Analysis Using the Exponential Model

4.3.3 Iterative Analysis Using the Exponential Model

4.3.4 The Need for Rapid Analysis

4.3.5 The Constant-Voltage Drop Model

4.3.6 The Ideal-Diode Model

4.3.7 The Small-Signal Model

4.3.8 Use of the Diode Forward Drop in Voltage Regulation

4.4 Operation in the Reverse Breakdown Region-Zener Diodes

4.4.1 Specifying and Modeling the Zener Diode

4.4.2 Use of the Zener as a Shunt Regulator

4.4.3 Temperature Effects

4.4.4 A Final Remark

4.5 Rectifier Circuits

4.5.1 The Half-Wave Rectifier

4.5.2 The Full-Wave Rectifier

4.5.3 The Bridge Rectifier

4.5.4 The Rectifier with a Filter Capacitor-The Peak Rectifier

4.5.5 Precision Half-Wave Rectifier-The Super Diode

4.6 Limiting and Clamping Circuits

4.6.1 Limiter Circuits

4.6.2 The Clamped Capacitor or DC Restorer

4.6.3 The Voltage Doubler

4.7 Special Diode Types

4.7.1 The Schottky-Barrier Diode (SBD)

4.7.2 Varactors

4.7.3 Photodiodes

4.7.4 Light-Emitting Diodes (LEDs)

Summary

Problems

Chapter 5. MOS Field-Effect Transistors (MOSFETs)

5.1 Device Structure and Physical Operation

5.1.1 Device Structure

5.1.2 Operation with Zero Gate Voltage

5.1.3 Creating a Channel for Current Flow

5.1.4 Applying a Small ?DS

5.1.5 Operation as ?DS is Increased

5.1.6 Operation for ?DS ? VOV

5.1.7 The p-Channel MOSFET

5.1.8 Complementary MOS or CMOS

5.1.9 Operating the MOS Transistor in the Subthreshold Region

5.2 Current-Voltage Characteristics

5.2.1 Circuit Symbol

5.2.2 The iD- ?DS Characteristics

5.2.3 The iD-nuGS Characteristic

5.2.4 Finite Output Resistance in Saturation

5.2.5 Characteristics of the p-Channel MOSFET

5.3 MOSFET Circuits at DC

5.4 Applying the MOSFET in Amplifier Design

5.4.1 Obtaining a Voltage Amplifier

5.4.2 The Voltage Transfer Characteristic (VTC)

5.4.3 Biasing the MOSFET to Obtain Linear Amplification

5.4.4 The Small-Signal Voltage Gain

5.4.5 Determining the VTC by Graphical Analysis

5.4.6 Locating the Bias Point Q

5.5 Small-Signal Operation and Models

5.5.1 The DC Bias Point

5.5.2 The Signal Current in the Drain Terminal

5.5.3 Voltage Gain

5.5.4 Separating the DC Analysis and the Signal Analysis

5.5.5 Small-Signal Equivalent Circuit Models

5.5.6 The Transconductance gm

5.5.7 The T Equivalent Circuit Model

5.5.8 Summary

5.6 Basic MOSFET Amplifier Configurations

5.6.1 The Three Basic Configurations

5.6.2 Characterizing Amplifiers

5.6.3 The Common-Source Configuration

5.6.4 The Common-Source Amplifier with a Source Resistance

5.6.5 The Common-Gate Amplifier

5.6.6 The Common-Drain Amplifier or Source Follower

5.6.7 Summary and Comparisons

5.7 Biasing in MOS Amplifier Circuits

5.7.1 Biasing by Fixing VGS

5.7.2 Biasing by Fixing VG and Connecting a Resistance in the Source

5.7.3 Biasing Using a Drain-to-Gate Feedback Resistance

5.7.4 Biasing Using a Constant-Current Source

5.7.5 A Final Remark

5.8 Discrete-Circuit MOS Amplifiers

5.8.1 The Basic Structure

5.8.2 The Common-Source (CS) Amplifier

5.8.3 The Common-Source Amplifier with a Source Resistance

5.8.4 The Common-Gate Amplifier

5.8.5 The Source Follower

5.8.6 The Amplifier Bandwidth

5.9 The Body Effect and Other Topics

5.9.1 The Role of the Substrate-The Body Effect

5.9.2 Modeling the Body Effect

5.9.3 Temperature Effects

5.9.4 Breakdown and Input Protection

5.9.5 Velocity Saturation

5.9.6 The Depletion-Type MOSFET

Summary

Problems

Chapter 6. Bipolar Junction Transistors (BJTs)

6.1 Device Structure and Physical Operation

6.1.1 Simplified Structure and Modes of Operation

6.1.2 Operation of the npn Transistor in the Active Mode

Current Flow

The Collector Current

The Base Current

The Emitter Current

Recapitulation and Equivalent-Circuit Models

6.1.3 Structure of Actual Transistors

6.1.4 Operation in the Saturation Mode

6.1.5 The pnp Transistor

6.2 Current-Voltage Characteristics

6.2.1 Circuit Symbols and Conventions

The Constant n

Collector-Base Reverse Current (ICBO)

6.2.2 Graphical Representation of Transistor Characteristics

6.2.3 Dependence of iC on the Collector Voltage-The Early Effect

6.2.4 An Alternative Form of the Common-Emitter Characteristics

The Common-Emitter Current Gain ?

The Saturation Voltage VCEsat and Saturation Resistance RCEsat

6.3 BJT Circuits at DC

6.4 Applying the BJT in Amplifier Design

6.4.1 Obtaining a Voltage Amplifier

6.4.2 The Voltage Transfer Characteristic (VTC)

6.4.3 Biasing the BJT to Obtain Linear Amplification

6.4.4 The Small-Signal Voltage Gain

6.4.5 Determining the VTC by Graphical Analysis

6.4.6 Locating the Bias Point Q

6.5 Small-Signal Operation and Models

6.5.1 The Collector Current and the Transconductance

6.5.2 The Base Current and the Input Resistance at the Base

6.5.3 The Emitter Current and the Input Resistance at the Emitter

6.5.4 Voltage Gain

6.5.5 Separating the Signal and the DC Quantities

6.5.6 The Hybrid-? Model

6.5.7 The T Model

6.5.8 Small-Signal Models of the pnp Transistor

6.5.9 Application of the Small-Signal Equivalent Circuits

6.5.10 Performing Small-Signal Analysis Directly on the Circuit Diagram

6.5.11 Augmenting the Small-Signal Model to Account for the Early Effect

6.5.12 Summary

6.6 Basic BJT Amplifier Configurations

6.6.1 The Three Basic Configurations

6.6.2 Characterizing Amplifiers

6.6.3 The Common-Emitter Amplifier

Characteristic Parameters of the CE Amplifier

Overall Voltage Gain

Alternative Gain Expressions

Performing the Analysis Directly on the Circuit

6.6.4 The Common-Emitter Amplifier with An Emitter Resistance

6.6.5 The Common-Base (CB) Amplifier

6.6.6 The Common-Collector Amplifier or Emitter Follower

The Need for Voltage Buffers

Characteristic Parameters of the Emitter Follower

Overall Voltage Gain

ThÃ©venin Representation of the Emitter Follower Output

6.6.7 Summary and Comparisons

6.7 Biasing in BJT Amplifier Circuits

6.7.1 The Classical Discrete-Circuit Biasing Arrangement

6.7.2 A Two-Power-Supply Version of the Classical Bias Arrangement

6.7.3 Biasing Using a Collector-to-Base Feedback Resistor

6.7.4 Biasing Using a Constant-Current Source

6.8 Discrete-Circuit BJT Amplifier

6.8.1 The Basic Structure

6.8.2 The Common-Emitter Amplifier

6.8.3 The Common-Emitter Amplifier with an Emitter Resistance

6.8.4 The Common-Base Amplifier

6.8.5 The Emitter Follower

6.8.6 The Amplifier Frequency Response

6.9 Transistor Breakdown and Temperature Effects

6.9.1 Transistor Breakdown

6.9.2 Dependence of ? on IC and Temperature

Summary

Problems

Part II. Integrated-Circuit Amplifiers

Chapter 7. Building Blocks of Integrated-Circuit Amplifiers

7.1 IC Design Philosophy

7.2 The Basic Gain Cell

7.2.1 The CS and CE Amplifiers with Current-Source Loads

7.2.2 The Intrinsic Gain

7.2.3 Effect of the Output Resistance of the Current-Source Load

7.2.4 Increasing the Gain of the Basic Cell

7.3 The Cascode Amplifier

7.3.1 Cascoding

7.3.2 The MOS Cascode

7.3.3 Distribution of Voltage Gain in a Cascode Amplifier

7.3.4 The Output Resistance of a Source-Degenerated CS Amplifier

7.3.5 Double Cascoding

7.3.6 The Folded Cascode

7.3.7 The BJT Cascode

7.3.8 The Output Resistance of an Emitter-Degenerated CE Amplifier

7.3.9 BiCMOS Cascodes

7.4 IC Biasing-Current Sources, Current Mirrors, and Current-Steering Circuits

7.4.1 The Basic MOSFET Current Source

7.4.2 MOS Current-Steering Circuits

7.4.3 BJT Circuits

7.5 Current-Mirror Circuits with Improved Performance

7.5.1 Cascode MOS Mirrors

7.5.2 A Bipolar Mirror with Base-Current Compensation

7.5.3 The Wilson Current Mirror

7.5.4 The Wilson MOS Mirror

7.5.5 The Widlar Current Source

7.6 Some Useful Transistor Pairings

7.6.1 The CC-CE, CD-CS, and CD-CE Configurations

7.6.2 The Darlington Configuration

7.6.3 The CC-CB and CD-CG Configurations

Summary

Appendix 7.A: Comparison of the MOSFET and BJT

7.A.1 Typical Values of IC MOSFET Parameters

7.A.2 Typical Values of IC BJT Parameters

7.A.3 Comparison of Important Characteristics

7.A.4 Combining MOS and Bipolar Transistors: BiCMOS Circuits

7.A.5 Validity of the Square-Law MOSFET Model

Problems

Chapter 8. Differential and Multistage Amplifiers

8.1 The MOS Differential Pair

8.1.1 Operation with a Common-Mode Input Voltage

8.1.2 Operation with a Differential Input Voltage

8.1.3 Large-Signal Operation

8.2 Small-Signal Operation of the MOS Differential Pair

8.2.1 Differential Gain

8.2.2 The Differential Half-Circuit

8.2.3 The Differential Amplifier with Current-Source Loads

8.2.4 Cascode Differential Amplifier

8.2.5 Common-Mode Gain and Common-Mode Rejection Ratio (CMRR)

8.3 The BJT Differential Pair

8.3.1 Basic Operation

8.3.2 Input Common-Mode Range

8.3.3 Large-Signal Operation

8.3.4 Small-Signal Operation

8.3.5 Common-Mode Gain and CMRR

8.4 Other Nonideal Characteristics of the Differential Amplifier

8.4.1 Input Offset Voltage of the MOS Differential Amplifier

8.4.2 Input Offset Voltage of the Bipolar Differential Amplifier

8.4.3 Input Bias and Offset Currents of the Bipolar Differential Amplifier

8.4.4 A Concluding Remark

8.5 The Differential Amplifier with Active Load

8.5.1 Differential to Single-Ended Conversion

8.5.2 The Active-Loaded MOS Differential Pair

8.5.3 Differential Gain of the Active-Loaded MOS Pair

8.5.4 Common-Mode Gain and CMRR

8.5.5 The Bipolar Differential Pair with Active Load

8.6 Multistage Amplifiers

8.6.1 A Two-Stage CMOS Op Amp

8.6.2 A Bipolar Op Amp

Summary

Problems

Chapter 9. Frequency Response

9.1 Low-Frequency Response of the CS and CE Amplifiers

9.1.1 The CS Amplifier

9.1.2 The CE Amplifier

9.2 Internal Capacitive Effects and the High-Frequency Model of the MOSFET and the BJT

9.2.1 The MOSFET

9.2.2 The BJT

9.3 High-Frequency Response of the CS and CE Amplifiers

9.3.1 The Common-Source Amplifier

9.3.2 The Common-Emitter Amplifier

9.4 Useful Tools for the Analysis of the High-Frequency Response of Amplifiers

9.4.1 The High-Frequency Gain Function

9.4.2 Determining the 3-dB Frequency fH

9.4.3 Using Open-Circuit Time Constants for the Approximate Determination of fH

9.4.4 Miller's Theorem

9.5 A Closer Look at the High-Frequency Response of the CS and CE Amplifiers

9.5.1 The Equivalent Circuit

9.5.2 Analysis Using Miller's Theorem

9.5.3 Analysis Using Open-Circuit Time Constants

9.5.4 Exact Analysis

9.5.5 Adapting the Formulas for the Case of the CE Amplifier

9.5.6 The Situation when Rsig is Low

9.6 High-Frequency Response of the CG and Cascode Amplifiers

9.6.1 High-Frequency Response of the CG Amplifier

9.6.2 High-Frequency Response of the MOS Cascode Amplifier

9.6.3 High-Frequency Response of the Bipolar Cascode Amplifier

9.7 High-Frequency Response of the Source and Emitter Followers

9.7.1 The Source Follower

9.7.2 The Emitter Follower

9.8 High-Frequency Response of Differential Amplifiers

9.8.1 Analysis of the Resistively Loaded MOS Amplifier

9.8.2 Analysis of the Active-Loaded MOS Amplifier

9.9 Other Wideband Amplifier Configurations

9.9.1 Obtaining Wideband Amplification by Source and Emitter Degeneration

9.9.2 The CD-CS, CC-CE and CD-CE Configurations

9.9.3 The CC-CB and CD-CG Configurations

9.10 High-Frequency Response of Multistage Amplifiers

9.10.1 Frequency Response of the Two-Stage CMOS Op Amp

9.10.2 Frequency Response of the Bipolar Op Amp of Section 8.5.2.

Summary

Problems

Chapter 10. Feedback

10.1 The General Feedback Structure

10.2 Some Properties of Negative Feedback

10.2.1 Gain Desensitivity

10.2.2 Bandwidth Extension

10.2.3 Noise Reduction

10.2.4 Reduction in Nonlinear Distortion

10.3 The Four Basic Feedback Topologies

10.3.1 Voltage Amplifiers

10.3.2 Current Amplifiers

10.3.3 Transconductance Amplifiers

10.3.4 Transresistance Amplifiers

10.3.5 A Concluding Remark

10.4 The Feedback Voltage-Amplifier (Series-Shunt)

10.4.1 The Ideal Case

10.4.2 The Practical Case

10.4.3 Summary

10.5 The Feedback Transconductance-Amplifier (Series-Series)

10.5.1 The Ideal Case

10.5.2 The Practical Case

10.5.3 Summary

10.6 The Feedback Transresistance-Amplifier (Shunt-Shunt)

10.6.1 The Ideal Case

10.6.2 The Practical Case

10.6.3 Summary

10.7 The Feedback Current-Amplifier (Shunt-Series)

10.7.1 The Ideal Case

10.7.2 The Practical Case

10.8 Summary of the Feedback Analysis Method

10.9 Determining the Loop Gain

10.9.1 An Alternative Approach for Finding A?

10.9.2 Equivalence of Circuits from a Feedback-Loop Point of View

10.10 The Stability Problem

10.10.1 The Transfer Function of the Feedback Amplifier

10.10.2 The Nyquist Plot

10.11 Effect of Feedback on the Amplifier Poles

10.11.1 Stability and Pole Location

10.11.2 Poles of the Feedback Amplifier

10.11.3 Amplifier with a Single-Pole Response

10.11.4 Amplifier with a Two-Pole Response

10.11.5 Amplifier with Three or More Poles

10.12 Stability Study Using Bode Plots

10.12.1 Gain and Phase Margins

10.12.2 Effect of Phase Margin on Closed-Loop Response

10.12.3 An Alternative Approach for Investigating Stability

10.13 Frequency Compensation

10.13.1 Theory

10.13.2 Implementation

10.13.3 Miller Compensation and Pole Splitting

Summary

Problems

Chapter 11. Output Stages and Power Amplifiers

11.1 Classification of Output Stages

11.2 Class A Output Stage

11.2.1 Transfer Characteristic

11.2.2 Signal Waveforms

11.2.3 Power Dissipation

11.2.4 Power Conversion Efficiency

11.3 Class B Output Stage

11.3.1 Circuit Operation

11.3.2 Transfer Characteristic

11.3.3 Power-Conversion Efficiency

11.3.4 Power Dissipation

11.3.5 Reducing Crossover Distortion

11.3.6 Single-Supply Operation

11.4 Class AB Output Stage

11.4.1 Circuit Operation

11.4.2 Output Resistance

11.5 Biasing the Class AB Circuit

11.5.1 Biasing Using Codes

11.5.2 Biasing Using the VBE Multiplier

11.6 CMOS Class AB Output Stages

11.6.1 The Classical Configuration

11.6.2 An Alternative Circuit Utilizing Common-Source Transistors

11.7 Power BJTs

11.7.1 Junction Temperature

11.7.2 Thermal Resistance

11.7.3 Power Dissipation versus Temperature

11.7.4 Transistor Case and Heat Sink

11.7.5 The BJT Safe Operating Area

11.7.6 Parameter Values of Power Transistors

11.8 Variations on the Class AB Configuration

11.8.1 Use of Input Emitter Followers

11.8.2 Use of Compound and Devices

11.8.3 Short-Circuit Protection

11.8.4 Thermal Shutdown

11.9 IC Power Amplifiers

11.9.1 A Fixed-Gain IC Power Amplifier

11.9.2 Power Op Amps

11.9.3 The Bridge Amplifier

11.10 MOS Power Transistors

11.10.1 Structure of the Power MOSFET

11.10.2 Characteristics of Power MOSFETs

11.10.3 Temperature Effects

11.10.4 Comparison with BJTs

11.10.5 A Class AB Output Stage Utilizing Power MOSFETs

Summary

Problems

Chapter 12. Operational Amplifier Circuits

12.1 The Two Stage CMOS Op Amp

12.1.1 The Circuit

12.1.2 Input Common-Mode Range and Output Swing

12.1.3 Voltage Gain

12.1.4 Common-Mode Rejection Ratio (CMRR)

12.1.5 Frequency Response

12.1.6 Slew Rate

12.1.7 Power-Supply Rejection Ratio (PSRR)

12.1.8 Design Tradeoffs

12.2 The Folded Cascode CMOS Op Amp

12.2.1 The Circuit

12.2.2 Input Common-Mode Range and Output Swing

12.2.3 Voltage Gain

12.2.4 Frequency Response

12.2.5 Slew Rate

12.2.6 Increasing the Input Common-Mode Range: Rail-to-Rail Input Operation

12.2.7 Increasing the Output Voltage Range: The Wide-Swing Current Mirror

12.3 The 741 Op-Amp Circuit

12.3.1 Bias Circuit

12.3.2 Short-Circuit Protection Circuitry

12.3.3 The Input Stage

12.3.4 The Second Stage

12.3.5 The Output Stage

12.3.6 Device Parameters

12.4 DC Analysis of the 741

12.4.1 Reference Bias Current

12.4.2 Input-Stage Bias

12.4.3 Input Bias and Offset Currents

12.4.4 Input Offset Voltage

12.4.5 Input Common-Mode Range

12.4.6 Second-Stage Bias

12.4.7 Output-Stage Bias

12.5 Small-Signal Analysis of the 741

12.5.1 The Input Stage

12.5.2 The Second Stage

12.5.3 The Output Stage

12.6 Gain Frequency Response, Slew Rage of the 741

12.6.1 Small-Signal Gain

12.6.2 Frequency Response

12.6.3 A Simplified Model

12.6.4 Slew Rate

12.6.5 Relationship Between ft and SR

12.7 Modern Techniques for the Design of BJT Op Amps

12.7.1 Special Performance Requirements

12.7.2 Bias Design

12.7.3 Design of Input Stage to Obtain Rail-to-Rail ?ICM

12.7.4 Common-Mode Feedback to Control the DC Voltage at the Output of the Input Stage

12.7.5 Output-Stage Design for Near Rail-to-Rail Output Swing

Summary

Problems

Part III. Digital Integrated Circuits

Chapter 13. CMOS Digital Logic Circuits

13.1 Digital Logic Inverters

13.1.1 Function of the Inverter

13.1.2 The Voltage Transfer Characteristic (VTC)

13.1.3 Noise Margins

13.1.4 The Ideal VTC

13.1.5 Inverter Implementation

13.1.6 Power Dissipation

13.1.7 Propagation Delay

13.1.8 Power-Delay and Energy-Delay Products

13.1.9 Silicon Area

13.1.10 Digital IC Technologies and Logic-Circuit Families

13.1.11 Styles for Digital System Design

13.1.12 Design Abstraction and Computer Aids

13.2 The CMOS Inverter

13.2.1 Circuit Operation

13.2.2 The Voltage Transfer Characteristic

13.2.3 The Situation When QN and QP are Not Matched

13.3 Dynamic Operation of the CMOS Inverter

13.3.1 Determining the Propagation Delay

13.3.2 Determining the Equivalent Load Capacitance C

13.3.3 Inverter Sizing

13.3.4 Dynamic Power Dissipation

13.4 CMOS Logic-Gate Circuits

13.4.1 Basic Structure

13.4.2 The Two-Input NOR Gate

13.4.3 The Two-Input NAND Gate

13.4.4 A Complex Gate

13.4.5 Obtaining the PUN from the PDN and Vice Versa

13.4.6 The Exclusive-OR Function

13.4.7 Summary of the Synthesis Method

13.4.8 Transistor Sizing

13.4.9 Effects of Fan-In and Fan-Out on Propagation Delay

13.5 Implications of Technology Scaling: Issues in Deep-Submicron Design

13.5.1 Scaling Implications

13.5.2 Velocity Saturation

13.5.3 Subthreshold Conduction

13.5.4 Wiring-The Interconnect

Summary

Problems

Chapter 14. Advanced MOS and Bipolar Logic Circuits

14.1 Pseudo-NMOS Logic Circuits

14.1.1 The Pseudo-NMOS Inverter

14.1.2 Static Characteristics

14.1.3 Derivation of the VTC

14.1.4 Dynamic Operation

14.1.5 Design

14.1.6 Gate Circuits

14.1.7 Concluding Remarks

14.2 Pass-Transistor Logic Circuits

14.2.1 An Essential Design Requirement

14.2.2 Operation with NMOS Transistors as Switches

14.2.3 Restoring the Value of VOH to VDD

14.2.4 The Use of CMOS Transmission Gates as Switches

14.2.5 Pass-Transistor Logic Circuit Examples

14.2.6 A Final Remark

14.3 Dynamic MOS Logic Circuits

14.3.1 The Basic Principle

14.3.2 Nonideal Effects

14.3.3 Domino CMOS Logic

14.3.4 Concluding Remarks

14.4 Emitter-Coupled Logic (ECL)

14.4.1 The Basic Principle

14.4.2 ECL Families

14.4.3 The Basic Gate Circuit

14.4.4 Voltage Transfer Characteristics

14.4.5 Fan-Out

14.4.6 Speed of Operation and Signal Transmission

14.4.7 Power Dissipation

14.4.8 Thermal Effects

14.4.9 The Wired-OR Capability

14.4.10 Final Remarks

14.5 BiCMOS Digital Circuits

14.5.1 The BiCMOS Inverter

14.5.2 Dynamic Operation

14.5.3 BiCMOS Logic Gates

Summary

Problems

Chapter 15. Memory Circuits

15.1 Latches and Flip-Flops

15.1.1 The Latch

15.1.2 The SR Flip-Flop

15.1.3 CMOS Implementation of SR Flip-Flops

15.1.4 A Simpler CMOS Implementation of the Clocked SR Flip-Flop

15.1.5 D Flip-Flop Circuits

15.2 Semiconductor Memories: Types and Architectures

15.2.1 Memory-Chip Organization

15.2.2 Memory-Chip Timing

15.3 Random-Access Memory (RAM) Cells

15.3.1 Static Memory (SRAM) Cell

15.3.2 Dynamic Memory (DRAM) Cell

15.4 Sense Amplifiers and Address Decoders

15.4.1 The Sense Amplifier

15.4.2 The Row-Address Decoder

15.4.3 The Column-Address Decoder

15.4.4 Pulse-Generation Circuits

15.5 Read-Only Memory (ROM)

15.5.1 A MOS ROM

15.5.2 Mask-Programmable ROMs

15.5.3 Programmable ROMs (PROMs and EPROMs)

Summary

Problems

Part IV. Filters and Oscillators

Chapter 16. Filters and Tuned Amplifiers

16.1 Filter Transmission, Types, and Specification

16.1.1 Filter Transmission

16.1.2 Filter Types

16.1.3 Filter Specification

16.2 The Filter Transfer Function

16.3 Butterworth and Chebyshev Filters

16.3.1 The Butterworth Filter

16.3.2 The Chebyshev Filter

16.4 First-Order and Second-Order Filter Functions

16.4.1 First-Order Filters

16.4.2 Second-Order Filter Functions

16.5 The Second-Order LCR Resonator

16.5.1 The Resonator Natural Modes

16.5.2 Realization of Transmission Zeros

16.5.3 Realization of the Low-Pass Function

16.5.4 Realization of the High-Pass Function

16.5.5 Realization of the Bandpass Function

16.5.6 Realization of the Notch Functions

16.5.7 Realization of the All-Pass Function

16.6 Second-Order Active Filters Based on Inductor Replacement

16.6.1 The Antoniou Inductance-Simulation Circuit

16.6.2 The Op Amp-RC Resonator

16.6.3 Realization of the Various Filter Types

16.6.4 The All-Pass Circuit

16.7 Second-Order Active Filters Based on the Two-Integrator-Loop Topology

16.7.1 Derivation of the Two-Integrator-Loop Biquad

16.7.2 Circuit Implementation

16.7.3 An Alternative Two-Integrator-Loop Biquad Circuit

16.7.4 Final Remarks

16.8 Single-Amplifier Biquadratic Active Filters

16.8.1 Synthesis of the Feedback Loop

16.8.2 Injecting the Input Signal

16.8.3 Generation of Equivalent Feedback Loops

16.9 Sensitivity

16.9.1 A Concluding Remark

16.10 Switched-Capacitor Filters

16.10.1 The Basic Principle

16.10.2 Practical Circuits

16.10.3 A Final Remark

16.11 Tuned Amplifiers

16.11.1 The Basic Principle

16.11.2 Inductor Losses

16.11.3 Use of Transformers

16.11.4 Amplifiers with Multiple Tuned Circuits

16.11.5 The Cascode and the CC-CB Cascade

16.11.6 Synchronous Tuning

16.11.7 Stagger-tuning

Summary

Problems

Chapter 17. Signal Generators and Waveform-Shaping Circuits

17.1 Basic Principles of Sinusoidal Oscillators

17.1.1 The Oscillator Feedback Loop

17.1.2 The Oscillation Criterion

17.1.3 Nonlinear Amplitude Control

17.1.4 A Popular Limiter Circuit for Amplitude Control

17.2 Op-Amp-RC Oscillator Circuits

17.2.1 The Wien-Bridge Oscillator

17.2.2 The Phase-Shift Oscillator

17.2.3 The Quadrature Oscillator

17.2.4 The Active-Filter-Tuned Oscillator

17.2.5 A Final Remark

17.3 LC and Crystal Oscillators

17.3.1 LC-Tuned Oscillators

17.3.2 Crystal Oscillators

17.4 Bistable Multivibrators

17.4.1 The Feedback Loop

17.4.2 Transfer Characteristics of the Bistable Circuit

17.4.3 Triggering the Bistable Circuit

17.4.4 The Bistable Circuit as a Memory Element

17.4.5 A Bistable Circuit with Noninverting Transfer Characteristics

17.4.6 Application of the Bistable Circuit as a Comparator

17.4.7 Making the Output Levels More Precise

17.5 Generation of Square and Triangular Waveforms Using Astable Multivibrators

17.5.1 Operation of the Astable Multivibrator

17.5.2 Generation of Triangular Waveforms

17.6 Generation of a Standardized Pulse-The Monostable Multivibrator

17.7 Integrated-Circuit Timers

17.7.1 The 555 Circuit

17.7.2 Implementing a Monostable Multivibrator Using the 555 IC

17.7.3 An Astable Multivibrator Using the 555 IC

17.8 Nonlinear Waveform-Shaping Circuits

17.8.1 The Breakpoint Method

17.8.2 The Nonlinear-Amplification Method

17.9 Precision Rectifier Circuits

17.9.1 Precision Half-Wave Rectifier-The 17.9.2 An Alternative Circuit

17.9.3 An Application: Measuring AC Voltages

17.9.4 Precision Full-Wave Rectifier

17.9.5 A Precision Bridge Rectifier for Instrumentation Applications

17.9.6 Precision Peak Rectifiers

17.9.7 A Buffered Precision Peak Detector

17.9.8 A Precision Clamping Circuit

Summary

Problems

PREFACE

Microelectronic Circuits, sixth edition, is intended as a text for the core courses in electronic

circuits taught to majors in electrical and computer engineering. It should also prove useful to

engineers and other professionals wishing to update their knowledge through self-study.

As was the case with the first five editions, the objective of this book is to develop in the

reader the ability to analyze and design electronic circuits, both analog and digital, discrete

and integrated. While the application of integrated circuits is covered, emphasis is placed on

transistor circuit design. This is done because of our belief that even if the majority of those

studying this book were not to pursue a career in IC design, knowledge of what is inside the

IC package would enable intelligent and innovative application of such chips. Furthermore,

with the advances in VLSI technology and design methodology, IC design itself is becoming

accessible to an increasing number of engineers.

Prerequisites

The prerequisite for studying the material in this book is a first course in circuit analysis.

As a review, some linear circuits material is included here in the appendices: specifically,

two-port network parameters in Appendix C; some useful network theorems in Appendix D;

single-time-constant circuits in Appendix E; and s-domain analysis in Appendix F. No prior

knowledge of physical electronics is assumed. All required semiconductor device physics is

included, and Appendix A provides a brief description of IC fabrication. All these appendices

can be found on the DVD that accompanies this book.

Emphasis on Design

It has been our philosophy that circuit design is best taught by pointing out the various tradeoffs available in selecting a circuit configuration and in selecting component values for a

given configuration. The emphasis on design has been increased in this edition by including

more design examples, simulation examples, exercise problems, and end-of-chapter problems. Those exercises and end-of-chapter problems that are considered â€œdesign-orientedâ€

are indicated with a D. Also, considerable material is provided on the most valuable design

aid, SPICE, including Appendix B, which is available on the DVD so that it can be offered

in searchable format, and in the full detail it deserves while not crowding other topics out of

the text.

xxi

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xxiiPreface

New to This Edition

Although the philosophy and pedagogical approach of the first five editions have been retained, several changes have been made to both organization and coverage.

1. Four-Part Organization. The book has been reorganized into four Parts. Part I:

Devices and Basic Circuits (Chapters 1-6) provides a coherent and comprehensive

single-semester introductory course in electronics. Similarly, Part II: IntegratedCircuit Amplifiers (Chapters 7-12) presents a rich package of material suitable for

a second course. Part III: Digital Integrated Circuits (Chapters 13-15) represents

a nearly self-contained coverage of digital electronics that can be studied after

Chapters 5 (MOSFETs) and 6 (BJTs), or even only 5 if the emphasis is on MOS

digital circuitsâ€”extremely helpful for teaching Computer Engineering students.

Finally, Part IV: Filters and Oscillators (Chapters 16-17), deals with more specific

application-oriented material that can be used to supplement a second course on

analog circuits, be part of a third course, or used as reading and reference material to

support student design projects. More on course design is given below.

2. Flexible organization. The most important feature of this edition is its flexible organization. Some manifestations of this flexibility are:

â€¢ MOSFETs and BJTs. Chapter 5 (MOSFETs) and Chapter 6 (BJTs) are written

to be completely independent of each other and thus can be taught in whatever

order the instructor desires. Because the two chapters have identical structures,

the chapter taught second can be covered much faster.

â€¢ Robust Digital Coverage. The digital material has been grouped together in

the new Part III, updated, and expanded. It can be covered at various points in

the first or second course. All that is needed by way of background is the material on the two transistor types (Chapters 5 and 6) or even just Chapter 5 since

most digital electronics today is MOS-based.

â€¢ Semiconductors as Needed. The required material on semiconductor physics

has been grouped together in a short chapter (Chapter 3) that can be taught,

skipped, or assigned as reading material, depending on the background of the

students and the instructorâ€™s teaching philosophy. This chapter serves as a

primer on the basics, or as a refresher, depending on whether students have had

a prior course in semiconductors.

â€¢ Op-amps Anywhere. The op-amp chapter (Chapter 2) can be taught at any

point in the first or second course, or skipped altogether if this material is taught

in other courses.

â€¢ Frequency Response. The material on amplifier frequency response has been

grouped together into a single chapter (Chapter 9). The chapter is organized in

a way that allows coverage of as few sections as the instructor deems necessary.

Also, some of the basic material (Sections 9.1 to 9.3) can be covered earlier

(after Chapters 5 or 6) as part of the first course.

â€¢ â€œMust-Coverâ€ Topics First. Each chapter is organized so that the essential

â€œmust-coverâ€ topics are placed first, and the more specialized material appears

last. More specialized material that can be skipped on a first reading, while

the student is first learning the basics, is marked with a . Once the students

understand the core concepts, they can return to these important but specialized

topics.

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Prefacexxiii

3. Streamlined MOSFETs and BJTs. Chapters 5 (MOSFETs) and 6 (BJTs) have been

rewritten to increase the clarity of presentation and emphasize essential topics. Also,

these chapters are now shorter and can be covered faster.

4. Cascode Configuration. A novel and intuitively appealing approach is used to introduce the cascode configuration in Chapter 7.

5. Comparison of MOSFETs and BJTs. The insightful comparison of the MOSFET

and the BJT has been moved to an appendix attached to Chapter 7. The appendix

also includes an update of the device parameter values corresponding to various

generations of fabrication process technologies. This appendix provides a good review and a reference that can be consulted at various points in a second course.

6. Feedback. The feedback chapter (Chapter 10) has been rewritten to increase clarity.

Also, a large number of new examples, mostly MOS-based, are included.

7. Class AB Amplifiers. New material on MOSFET class AB amplifiers is included

in Chapter 11.

8. Low-Voltage Bipolar Design. While the classical 741 op-amp circuit is retained,

a new section on modern techniques for the design of low-voltage bipolar op amps

has been added to Chapter 12.

9. Deep-Submicron Design. In addition to augmenting and consolidating the material

on digital electronics in Part III, a new section on technology scaling (Mooreâ€™s Law)

and deep-submicron design issues has been added (Chapter 13).

10. MOS Emphasis. Throughout the book, greater emphasis is placed on MOS circuits

to reflect the current dominance of the MOSFET in electronics.

11. Bonus Reading on DVD. Supplementary material on a wide variety of topics that

were included in previous editions is made available on the DVD accompanying the

book (see a listing below).

12. Examples, Exercises, and Problems. The number of Examples has been increased.

Also, the in-chapter Exercises and end-of-chapter Problems have been updated with

parameter values of current technologies so students work with a real-world perspective on technology. More Exercises and Problems, of a greater variety, have

been added.

13. Summary Tables. As a study aid and for easy reference, many summary tables are

included. See the complete List of Summary Tables after the Table of Contents.

14. Learning Objectives. A new section (In This Chapter You Will Learnâ€¦) has been

added at the beginning of each chapter to focus attention on the major learning

objectives of the chapter.

15. SPICE. A significant number of new simulation examples using National Instrumentsâ„¢ Multisimâ„¢ are added to the Cadence PSpiceÂ® simulation examples. Together with a section describing the SPICE device models, these design and simulation examples are grouped together in Appendix B. They can also be found together

with other simulation files in the Lab-on-a-Disc on the DVD.

16. Simulation. A number of end-of-chapter Problems in each chapter are marked with

the SIM icon

as simulation problems. Students attempting these problems will

find considerable additional guidance on the DVD.

17. Key Equations. All equations that will be cross-referenced and used again are numbered. Particularly important equations are marked with a special icon.

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xxivPreface

As well as the structural differences described above, new coverage is included on all of the

following technical topics.

â€¢ Entirely rewritten coverage of semiconductors (Chapter 3)

â€¢ MOSFET and BJT chapters extensively rewritten and restructured, with new

figures and examples (Chapter 5 and 6)

â€¢ The basic gain cell (Chapter 7)

â€¢ The cascode amplifier (Chapter 7)

â€¢ CC-CE, CD-CS, and CD-CE transistor configurations (Chapter 7)

â€¢ CMRR (Chapter 8)

â€¢ The differential amplifier with active load (Chapter 8)

â€¢ Determining the output resistance Ro (Chapter 8)

â€¢ All new sections on frequency response (Chapter 9)

â€¢ Many, many new MOS examples of feedback (Chapter 10)

â€¢ CMOS class AB output stages (Chapter 11)

â€¢ Rejection ratios (CMRR and PSRR) (Chapter 12)

â€¢ Modern techniques for the design of BJT op amps (Section 12.7)

â€¢ Digital logic inverters (Chapter 13)

â€¢ The CMOS inverter (Chapter 13)

â€¢ Deep submicron design and technology scaling (Mooreâ€™s Law) (Section 13.5)

The DVD and the Website

A DVD accompanies this book. It contains much useful supplementary information and material intended to enrich the studentâ€™s learning experience. These include

1. Student versions of both Cadence PSpiceÂ® and National Instrumentsâ„¢ Multisimâ„¢.

2. The input files for all the PSpiceÂ® and Multisimâ„¢ examples in this book.

3. Step-by-step guidance to help with the simulation Examples and end-of-chapter

Problems identified with a

icon.

4. A link to the bookâ€™s website, offering PowerPoint slides of every figure in this book

that students can print and carry to class to facilitate taking notes.

5. Bonus text material of specialized topics not covered in the current edition of the

textbook. These include:

â€¢ Junction Field-Effect Transistors (JFETs)

â€¢ Gallium Arsenide (GaAs) devices and circuits

â€¢ Transistor-Transistor Logic (TTL) circuits

â€¢ Analog-to-Digital and Digital-to-Analog converter circuits

6. Appendices for the book:

â€¢ Appendix A: VLSI Fabrication Technology

â€¢ Appendix B: SPICE Device Models and Design and Simulation Examples Using PSpiceÂ® and Multisimâ„¢

â€¢ Appendix C: Two-Port Network Parameters

â€¢ Appendix D: Some Useful Network Theorems

â€¢ Appendix E: Single-Time-Constant Circuits

â€¢ Appendix F: s-domain Analysis: Poles, Zeroes, and Bode Plots

â€¢ Appendix G: Bibliography

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Prefacexxv

A website for the book has been set up (www.oup.com/us/sedrasmith, or www.sedrasmith.

org). Its content will change frequently to reflect new developments in the field. On the site,

PowerPoint-based slides of all the figures in the text are available for easy note-taking. The

website also features datasheets for hundreds of useful devices to help in laboratory experiments, links to industrial and academic websites of interest, and a message center to communicate with the authors and with Oxford University Press.

Exercises and End-of-Chapter Problems

Over 475 Exercises are integrated throughout the text. The answer to each exercise is given

below the exercise so students can check their understanding of the material as they read.

Solving these exercises should enable the reader to gauge his or her grasp of the preceding

material. In addition, more than 1450 end-of-chapter Problems, 55% of which are new or revised in this edition, are provided. The problems are keyed to the individual chapter sections

and their degree of difficulty is indicated by a rating system: difficult problems are marked

with an asterisk (*); more difficult problems with two asterisks (**); and very difficult (and/

or time consuming) problems with three asterisks (***). We must admit, however, that this

classification is by no means exact. Our rating no doubt depended to some degree on our

thinking (and mood!) at the time a particular problem was created. Answers to sample problems are given in Appendix I, so students have a checkpoint to tell if they are working out

the problems correctly. Complete solutions for all exercises and problems are included in the

Instructorâ€™s Solutions Manual, which is available from the publisher to those instructors who

adopt the book.

As in the previous five editions, many examples are included. The examples, and indeed

most of the problems and exercises, are based on real circuits and anticipate the applications

encountered in designing real-life circuits. This edition continues the use of numbered solution steps in the figures for many examples, as an attempt to recreate the dynamics of the

classroom.

Course Organization

The book contains sufficient material for a sequence of two single-semester courses (each

of 40-50 lecture hours). The organization of the book provides considerable flexibility for

course design. In the following, we suggest various possibilities for the two courses. This is

also laid out in an easy-to-follow visual form at the beginning of the Instructorâ€™s Edition of

the book.

The First Course

At the core of the first course are Chapters 4 (Diodes), 5 (MOSFETs), and 6 (BJTs). Of

these three, the MOSFET chapter is the one that has to be covered most thoroughly. If it is

covered before the BJT, and we recommend that it should be, then the BJT chapter can be

covered much faster. If time does not permit, some of the later sections in Chapter 4 can be

skipped. Chapter 1 (Signals and Amplifiers) deserves some treatment in class. Although the

signal concepts can be assigned as out-of-class reading, the amplifier material should be

discussed. However, if frequency response is not emphasized in the first course, Section 1.6

can be skipped.

Around this core, one can build three possible curricula for the first course:

1. Standard: Chapters 1â€“6. Here, some or all of Chapter 2 (Op Amps) can be delayed.

Also, the decision as to how much to cover of Chapter 3 (Semiconductors) will

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xxviPreface

depend on the studentsâ€™ background and the instructorâ€™s philosophy. If desired, this

course can be supplemented by the material on amplifier frequency response in Sections 9.1â€“9.3.

2. Digital Orientation: Chapters 1 (without Section 1.6), 4 (without the later applications sections), all of 5, 6 (perhaps focusing only on the early sections), Section 9.2,

and Chapters 13, 14, and 15. If time constraints are a concern, coverage of 6 can be

shortened; Section 13.5 on Mooreâ€™s Law and deep-submicron design can be skipped,

and Sections 14.4 and 14.5 that depend on BJTs can be omitted. This course is ideal

for Computer Engineering students.

3. Analog Orientation. Chapters 1, 4 (perhaps without all of the later, more applicationoriented sections), 5, 6, 7 (without the advanced material in 7.6), 8, 9 (including at

least 9.1â€“9.3, and the instructorâ€™s selection of other topics), and 10 (a selection of

topics). This is a heavy course, and assumes that the students have previously covered op amps and maybe diodes, as well as device physics. This course is ideal where

the first electrical engineering course is a hybrid of circuits and basic electronics, and

where students have taken a semiconductor device physics course.

The Second Course

There are three possibilities for the second course:

1. Standard: Chapters 7â€“12. If time does not permit, some of the later sections in Chapter 9 can be skipped. Also, some of the more advanced topics in Chapters 11 and 12

can be skipped. If desired, some material from Chapter 16 (Filters) and Chapters

17 (Oscillators) can be included. This course ideally follows the â€œStandard First

Courseâ€ outlined above.

2. Analog and Digital Combination: Chapters 7, 8, 9 (selection of topics); 10 (selection

of topics), 13 (perhaps without Section 13.5 on technology scaling), 14 (omitting

14.4 and 14.5 if time is short), and 15 (selection of topics).

3. Electrical Follow-up: Chapters 6, 7, 8, 9, 10, and a choice of topics as time allows,

selected from Chapters 11 and 12. This course is ideal for Electrical Engineering

students who took a first semester with a â€œDigital Orientationâ€ outlined above to

accommodate Computer Engineering students.

Supplementary Material/Third Course

Chapters 16 (Filters) and 17 (Oscillators) contain material that can be used to supplement a

third course on analog circuits. As well, this material is highly design-oriented and can be

used to aid students who are pursuing design projects.

Chapters 13, 14, and 15 can be used as about half (15 hours of lecture) of a senior level

course on digital IC design.

An Outline for the Reader

Part I, Devices and Basic Circuits, includes the most fundamental and essential topics for

the study of electronic circuits. At the same time, it constitutes a complete package for a first

course on the subject.

Chapter 1. The book starts with an introduction to the basic concepts of electronics in

Chapter 1. Signals, their frequency spectra, and their analog and digital forms are presented.

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Prefacexxvii

Amplifiers are introduced as circuit building blocks and their various types and models are

studied. This chapter also establishes some of the terminology and conventions used throughout the text.

Chapter 2. Chapter 2 deals with operational amplifiers, their terminal characteristics,

simple applications, and practical limitations. We chose to discuss the op amp as a circuit

building block at this early stage simply because it is easy to deal with and because the student can experiment with op-amp circuits that perform nontrivial tasks with relative ease

and with a sense of accomplishment. We have found this approach to be highly motivating

to the student. We should point out, however, that part or all of this chapter can be skipped

and studied at a later stage (for instance, in conjunction with Chapter 8, Chapter 10, and/or

Chapter 12) with no loss of continuity.

Chapter 3. Chapter 3 provides an overview of semiconductor concepts at a level sufficient for understanding the operation of diodes and transistors in later chapters. Coverage

of this material is useful in particular for students who have had no prior exposure to device

physics. Even those with such a background would find a review of Chapter 3 beneficial as

a refresher. The instructor can choose to cover this material in class or assign it for outside

reading.

Chapter 4. The first electronic device, the diode, is studied in Chapter 4. The diode

terminal characteristics, the circuit models that are used to represent it, and its circuit applications are presented. Depending on the time available in the course, some of the diode

applications (e.g., Section 4.6) can be skipped. Also, the brief description of special diode

types (Section 4.7) can be left for the student to read.

Chapters 5 and 6. The foundation of electronic circuits is established by the study of

the two transistor types in use today: the MOS transistor in Chapter 5 and the bipolar transistor in Chapter 6. These are the two most important chapters of the book. These two chapters

have been written to be completely independent of one another and thus can be studied in

either order, as desired. Furthermore, the two chapters have the same structure, making it

easier and faster to study the second device, as well as to draw comparisons between the two

device types.

Each of Chapters 5 and 6 begins with a study of the device structure and its physical

operation, leading to a description of its terminal characteristics. Then, to allow the student to

become very familiar with the operation of the transistor as a circuit element, a large number

of examples are presented of dc circuits utilizing the device. We then ask: How can the transistor be used as an amplifier? To answer the question we consider the large-signal operation

of the basic common-source (common-emitter) circuit and use it to delineate the regions over

which the device can be used as a linear amplifier, from those regions where it can be used

as a switch. We then pursue the small-signal operation of the transistor and develop circuit

models for its representation. The various configurations in which the transistor can be used

as an amplifier are then studied and contrasted. This is followed by a study of methods to

bias the transistor to operate as an amplifier in discrete-circuit applications. We then put everything together by presenting complete practical discrete-circuit transistor amplifiers. The

last section of each of Chapters 5 and 6 deals with second-order effects that are included for

completeness, but that can be skipped if time does not permit detailed coverage.

After the study of Part I, the reader will be fully prepared to study either integratedcircuit amplifiers in Part II, or digital integrated circuits in Part III.

Part II, Integrated-Circuit Amplifiers, is devoted to the study of practical amplifier circuits that can be fabricated in the integrated-circuit (IC) form. Its six chapters constitute a

coherent treatment of IC amplifier design and can thus serve as a second course in electronic

circuits.

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xxviiiPreface

Chapter 7. Beginning with a brief introduction to the philosophy of IC design, Chapter 7

presents the basic circuit building blocks that are used in the design of IC amplifiers. We start

with the basic gain cell comprising a common-source (common-emitter) transistor loaded

with a current source, and ask: How can we increase its voltage gain? This leads naturally to

the concept of cascoding and its use in the cascode amplifier and the cascode current source.

We then consider the methods used for biasing IC amplifiers. The chapter concludes, as do

most chapters in the book, with advanced topics (Sections 7.5 and 7.6) that can be skipped if

the instructor is pressed for time.

Chapter Appendix 7.A. Chapter 7 includes an appendix that provides a comprehensive

compilation and comparison of the properties of the MOSFET and the BJT. The comparison

is aided by the inclusion of typical parameter values of devices fabricated with modern process technologies. This appendix can be consulted at any point from Chapter 7 on, and should

serve as a concise review of the important characteristics of both transistor types.

MOS and Bipolar. Throughout Part II, both MOS and bipolar circuits are presented

side-by-side. Because the MOSFET is by far the dominant device, its circuits are presented

first. Bipolar circuits are discussed to the same depth but occasionally more briefly.

Chapter 8. The most important IC building block, the differential pair, is the main topic

of Chapter 8. The last section of Chapter 8 is devoted to the study of multistage amplifiers.

Chapter 9. Chapter 9 presents a comprehensive treatment of the important subject of

amplifier frequency response. Here, Sections 9.1, 9.2, and 9.3 contain essential material; Sections 9.4 and 9.5 provide an in-depth treatment of very useful new tools; and Sections 9.6 to

9.10 present the frequency response analysis of a variety of amplifier configurations that can

be studied as and when needed. A selection of the latter sections can be made depending on

the time available and the instructorâ€™s preference.

Chapter 10. The fourth of the essential topics of Part II, feedback, is the subject of

Chapter 10. Both the theory of negative feedback and its application in the design of practical

feedback amplifiers are presented. We also discuss the stability problem in feedback amplifiers and treat frequency compensation in some detail.

Chapter 11. In Chapter 11 we switch gears from dealing with small-signal amplifiers

to those that are required to handle large signals and large amounts of power. Here we study

the different amplifier classesâ€”A, B, and ABâ€”and their realization in bipolar and CMOS

technologies. We also consider power BJTs and power MOSFETs, and study representative

IC power amplifiers. Depending on the availability of time, some of the later sections (e.g.,

11.8â€“11.10 on special applications) can be skipped in a first reading.

Chapter 12. Finally, Chapter 12 brings together all the topics of Part II in an important

application; namely, the design of operational amplifier circuits. We study both CMOS and

bipolar op amps. In the latter category, besides the classical and still timely 741 circuit, we

present modern techniques for the design of low-voltage op amps (Section 12.7).

Part III, Digital Integrated Circuits, provides a brief but nonetheless comprehensive and

sufficiently detailed study of digital IC design. Our treatment is almost self-contained, requiring for the most part only a thorough understanding of the MOSFET material presented in

Chapter 5. Thus, Part III can be studied right after Chapter 5. The only exceptions to this are

the last two sections in Chapter 14 which require knowledge of the BJT (Chapter 6). Also,

knowledge of the MOSFET internal capacitances (Section 9.2.2) will be needed.

Chapter 13. Chapter 13 is the foundation of Part III. It begins with digital logic inverters (Section 13.1), and then concentrates on the bread-and-butter topics of digital IC design:

the CMOS inverter (Sections 13.2 and 13.3) and CMOS logic gates (Section 13.4). The last

section (13.5) deals with the implications of technology scaling (Mooreâ€™s law) and discusses

important issues in deep-submicron technologies. With the possible exception of Section

13.5, the material in Chapter 13 is the minimum needed to learn something meaningful about

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Prefacexxix

digital circuits.

Chapter 14. Chapter 14 builds on the foundation established in Chapter 13 and presents three important types of MOS logic circuits. As well, a significant family of bipolar

logic circuits, emitter-coupled logic, is studied. The chapter concludes with an interesting

digital circuit technology that attempts to combine the best attributes of bipolar and CMOS:

BiCMOS.

Chapter 15. Digital circuits can be broadly divided into logic and memory circuits. The

latter is the subject of Chapter 15.

Part IV, Filters and Oscillators, is intentionally oriented toward applications and systems. The two topics illustrate powerfully and dramatically the application of both negative

and positive feedback.

Chapter 16. Chapter 16 deals with the design of filters, which are important building

blocks of communication and instrumentation systems. A comprehensive, design-oriented

treatment of the subject is presented. The material provided should allow the reader to perform a complete filter design, starting from specification and ending with a complete circuit

realization. A wealth of design tables is included.

Chapter 17. Chapter 17 deals with circuits for the generation of signals with a variety

of waveforms: sinusoidal, square, and triangular. We also present circuits for the nonlinear

shaping of waveforms.

Appendices. The eight appendices contain much useful background and supplementary

material. We wish to draw the readerâ€™s attention in particular to the first two: Appendix A

provides a concise introduction to the important topic of IC fabrication technology including

IC layout. Appendix B provides SPICE device models as well as a large number of design

and simulation examples in PSpiceÂ® and Multisimâ„¢. The examples are keyed to the book

chapters. These Appendices and a great deal more material on these simulation examples can

be found on the DVD accompanying the book.

Ancillaries

A complete set of ancillary materials is available with this text to support your course.

For the Instructor

The Instructorâ€™s Solutions Manual provides complete worked solutions to all the exercises in

each chapter and all the end-of-chapter problems in the text.

The Instructorâ€™s Resource CD is bound into the Instructorâ€™s Solutions Manual so

instructors can find all their support materials in one place. The Resource CD contains

PowerPoint-based slides of every figure in the book and each corresponding caption. The

slides can be projected in class, added to a course management system, printed as overhead

transparencies, or used as handouts. The CD also contains complete solutions and instructorâ€™s support for the Lab-on-a-Disc simulation problems. (ISBN 9780195340303)

For the Student and Instructor

The DVD included with every new copy of the textbook contains Lab-on-a-Disc simulation

activities in Multisimâ„¢ and PSpiceÂ® for many of the simulation Examples and Problems in

the text. It also contains a Student Edition of Cadence PSpiceÂ® v. 16.2 Demo software, and a

Student Edition of National Instrumentsâ„¢ Multisimâ„¢ version 10.1.1, both of which can be

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xxxPreface

run by students on their own computers so they can practice their coursework wherever they

happen to study. Bonus text topics, the Appendices, and a link to the bookâ€™s website featuring manufacturer datasheets and PowerPoint-based slides of all of the bookâ€™s illustrations,

complete the DVD.

Acknowledgments

Many of the changes in this sixth edition were made in response to feedback received from

instructors who adopted the fifth edition. We are grateful to all those who took the time to

write to us. In addition, dozens of reviewers provided detailed commentary on the fifth edition and suggested many of the changes that we have incorporated in this revision. They are

listed later; to all of them, we extend our sincere thanks.

A number of individuals made significant contributions to this edition. Sam Emaminejad

and Muhammad Faisal prepared the Multisimâ„¢ and new PSpiceÂ® simulations and helped

with many aspects of the manuscript preparation. Olivier Trescases of the University of Toronto and his students helped immensely, independently testing all the simulations in the

Lab-on-a-Disc. Wai-Tung Ng of the University of Toronto rewrote Appendix A. Gordon

Roberts of McGill University gave us permission to use some of the examples from the book

SPICE 2nd edition, by Roberts and Sedra. Sima Dimitrijev of Griffith University undertook a

detailed review of Chapter 3 on semiconductor devices, and David Pulfrey of the University

of British Columbia offered suggestions as well. As in the previous edition, Anas Hamoui of

McGill University was the source of many good ideas. Jim Somers of Sonora Designworks

prepared discs for the student and instructor support materials. Jennifer Rodrigues typed all

the revisions with skill and good humor and assisted with many of the logistics. Linda Lyman assisted with more details than we can possibly list here, and has been invaluable. Laura

Fujino assisted in proofreading, and perhaps most importantly, in keeping one of us (KCS)

focused. To all of these friends and colleagues we say thank you.

We are also grateful to the following colleagues and friends who have provided many

helpful suggestions: Anthony Chan-Carusone, University of Toronto; Roman Genov, University of Toronto; David Johns, University of Toronto; Ken Martin, University of Toronto;

David Nairn, University of Waterloo; Wai-Tung Ng, University of Toronto; Khoman Phang,

University of Toronto; Gordon Roberts, McGill University; and Ali Sheikholeslami, University of Toronto.

The authors would like to thank Cadence and National Instruments for allowing Oxford

University Press to distribute the PSpiceÂ® and Multisimâ„¢ software with this book. Mark

Walters of National Instruments in particular has been very supportive. We are grateful to

PMC Sierra for the excellent cover photo (which is fully described on the copyright page of

this book, for readers who are interested in the intriguing technology shown here).

A large number of people at Oxford University Press contributed to the development of

this edition and its various ancillaries. We would like to specifically mention Art Director

Paula Schlosser and designers Dan Niver, Binbin Li, and Annika Sarin, Senior Copywriter

Jill Crosson, as well as Susanne Arrington, Andy Battle, Brian Black, Sonya Borders, Gigi

Brienza, Jim Brooks, Chris Critelli, Michael Distler, Diane Erickson, Ned Escobar, Adam

Glazer, Chris Hellstrom, Andrea Hill, Adriana Hurtado, Holly Lewis, Jenny Lupica, Johanna

Marcelino, Bill Marting, Laura Mahoney, Joella Molway, Preeti Parasharami, Emily Pillars,

Terry Retchless, Kim Rimmer, Linda Roths, Sarah Smith, Patrick Thompson, Adam Tyrell,

Euan White, and David Wright.

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Prefacexxxi

We wish to extend special thanks to our Publisher at Oxford University Press, John

Challice, and to the hardworking editorial team of Engineering Associate Editor Rachael

Zimmermann and Editorial Director Patrick Lynch, who have meticulously prepared all the

ancillary support for this book. Steve Cestaro, Director of Editorial, Design, and Production,

pulled out all the stops on this edition. Barbara Mathieu, Senior Production Editor, worked

quietly, cheerfully, and tirelessly to bring this book to completion under significant pressure,

making a difficult job look easy with grace and creativity. And last but certainly not least, a

special note of thanks and gratitude to our Development Editor, Danielle Christensen, who

was our main point of contact with OUP throughout the entire project and who managed the

project with creativity, thoughtfulness, and dedication.

Finally, we wish to thank our families for their support and understanding, and to thank

all the students and instructors who have valued this book throughout its history.

Adel S. Sedra

Kenneth C. (KC) Smith

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xxxiiPreface

Problem Solvers and Accuracy Checkers, Solutions Manual

Mandana Amiri, University of British Columbia, BC

Alok Berry, George Mason University, VA

Marc Cahay, University of Cincinnati, OH

Yun Chiu, University of Illinoisâ€“Urbana-Champaign, IL

Norman Cox, Missouri University of Science and Technology, MO

John Davis, University of Texasâ€“Austin, TX

Michael Green, University of Californiaâ€“Irvine, CA

Roger King, University of Toledo, OH

Clark Kinnaird, Southern Methodist University, TX

Robert Krueger, University of Wisconsinâ€“Milwaukee, WI

Shahriar Mirabbasi, University of British Columbia, BC

Daniel Moore, Rose-Hulman Institute of Technology, IN

Kathleen Muhonen, The Pennsylvania State University, PA

Angela Rasmussen, University of Utah, UT

Roberto Rosales, University of British Columbia, BC

John Wilson, Royal Military College, ON

Reviewers of the Sixth Edition

Elizabeth Brauer, Northern Arizona University, AZ

Martin Brooke, Duke University, NC

Yun Chiu, University of Illinoisâ€“Urbana-Champaign, IL

Norman Cox, Missouri University of Science and Technology, MO

Robert Bruce Darling, University of Washington, WA

John Davis, University of Texasâ€“Austin, TX

Christopher DeMarco, University of Wisconsinâ€“Madison, WI

Robert Engelken, Arkansas State University, AR

Ethan Farquhar, University of Tennessee, TN

Patrick Fay, University of Notre Dame, IN

George Giakos, University of Akron, OH

John Gilmer, Wilkes University, PA

Tayeb Giuma, University of North Florida, FL

Michael Green, University of Californiaâ€“Irvine, CA

Steven de Haas, California State Universityâ€“Sacramento, CA

Anas Hamoui, McGill University, QC

William Harrell, Clemson University, SC

Reid Harrison, University of Utah, UT

Timothy Horiuchi, University of Marylandâ€“College Park, MD

Mohammed Ismail, The Ohio State University, OH

Paul Israelson, Utah State University, UT

Zhenhua Jiang, University of Miami, FL

Seongsin M. Kim, University of Alabama, AL

Roger King, University of Toledo, OH

Clark Kinnaird, Southern Methodist University, TX

Tsu-Jae King Liu, University of Californiaâ€“Berkeley, CA

Yicheng Lu, Rutgers University, NJ

David Nairn, University of Waterloo, ON

Thomas Matthews, California State Universityâ€“Sacramento, CA

Ken Noren, University of Idaho, ID

Brita Olson, California Polytechnic Universityâ€“Pomona, CA

Martin Peckerar, University of Marylandâ€“College Park, MD

Khoman Phang, University of Toronto, ON

Mahmudur Rahman, Santa Clara University, CA

John Ringo, Washington State University, WA

Norman Scheinberg, City College, NY

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Prefacexxxiii

Kuang Sheng, Rutgers University, NJ

Andrew Szeto, San Diego State University, CA

Joel Therrien, University of Massachusettsâ€“Lowell, MA

Len Trombetta, University of Houston, TX

Mustapha C.E. Yagoub, University of Ottawa, ON

Donna Yu, North Carolina State University, NC

Jiann-Shiun Yuan, University of Central Florida, FL

Sandra Yost, University of Detroitâ€“Mercy, MI

Jianhua (David) Zhang, University of Illinoisâ€“Urbana-Champaign, IL

Reviewers of Prior Editions

Maurice Aburdene, Bucknell University, PA

Michael Bartz, University of Memphis, TN

Patrick L. Chapman, University of Illinoisâ€”Urbana-Champaign, IL

Roy H. Cornely, New Jersey Institute of Technology, NJ

Dale L. Critchlow, University of Vermont, VT

Artice Davis, San Jose State University, CA

Eby G. Friedman, University of Rochester, NY

Paul M. Furth, New Mexico State University, NM

Rhett T. George, Jr., Duke University, NC

Roobik Gharabagi, St. Louis University, MO

Steven de Haas, California State Universityâ€”Sacramento, CA

Reza Hashemian, Northern Illinois University, IL

Ward J. Helms, University of Washington, WA

Richard Hornsey, York University, ON

Hsiung Hsu, The Ohio State University, OH

Robert Irvine, California State Polytechnic Universityâ€”Pomona, CA

Steve Jantzi, Broadcom

Marian Kazimierczuk, Wright State University, OH

John Khoury, Columbia University, NY

Jacob B. Khurgin, The Johns Hopkins University, MD

Roger King, University of Toledo, OH

Robert J. Krueger, University of Wisconsinâ€”Milwaukee, WI

Joy Laskar, Georgia Institute of Technology, GA

David Luke, University of New Brunswick, NB

Un-Ku Moon, Oregon State University, OR

Bahram Nabet, Drexel University, PA

Dipankar Nagchoudhuri, Indian Institute of Technologyâ€”Delhi, India

David Nairn, Analog Devices

Joseph H. Nevin, University of Cincinnati, OH

Rabin Raut, Concordia University, QC

John A. Ringo, Washington State University, WA

Zvi S. Roth, Florida Atlantic University, FL

Mulukutla Sarma, Northeastern University, MA

John Scalzo, Louisiana State University, LA

Pierre Schmidt, Florida International University, FL

Richard Schreier, Analog Devices

Dipankar Sengupta, Royal Melbourne Institute of Technology, Australia

Ali Sheikholeslami, University of Toronto, ON

Michael L. Simpson, University of Tennessee, TN

Karl A. Spuhl, Washington University in St. Louis, MO

Charles Sullivan, Dartmouth College, NH

Daniel van der Weide, University of Delaware, DE

Gregory M. Wierzba, Michigan State University, MI

Alex Zaslavsky, Brown University, RI

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PART I

Devices and

Basic Circuits

CHAPTER 1

Signals and Amplifiers

4

CHAPTER 2

Operational Amplifiers

52

CHAPTER 3

Semiconductors

124

CHAPTER 4

Diodes

164

CHAPTER 5

MOS Field-Effect Transistors (MOSFETs)

CHAPTER 6

Bipolar Junction Transistors (BJTs)

350

230

P

art I, Devices and Basic Circuits, includes the most fundamental and essential topics

for the study of electronic circuits. At the same time, it constitutes a complete package for a first course on the subject.

The heart of Part I is the study of the three basic semiconductor devices: the diode

(Chapter 4); the MOS transistor (Chapter 5); and the bipolar transistor (Chapter 6). In each

case, we study the device operation, its characterization, and its basic circuit applications.

For those who have not had a prior course on device physics, Chapter 3 provides an overview of semiconductor concepts at a level sufficient for the study of electronic circuits. A

review of Chapter 3 should prove useful even for those with prior knowledge of semiconductors.

Since the purpose of electronic circuits is the processing of signals, an understanding

is essential of signals, their characterization in the time and frequency domains, and their

analog and digital representations. This is provided in Chapter 1, which also introduces

the most common signal-processing function, amplification, and the characterization

and types of amplifiers.

Besides diodes and transistors, the basic electronic devices, the op amp is studied in

Part I. Although not an electronic device in the most fundamental sense, the op amp is

commercially available as an integrated circuit (IC) package and has well-defined terminal characteristics. Thus, despite the fact that the op ampâ€™s internal circuit is complex, typically incorporating 20 or more transistors, its almost-ideal terminal behavior makes it

possible to treat the op amp as a circuit element and to use it in the design of powerful

circuits, as we do in Chapter 2, without any knowledge of its internal construction. We

should mention, however, that the study of op amps can be delayed to a later point, and

Chapter 2 can be skipped with no loss of continuity.

The foundation of this book, and of any electronics course, is the study of the two

transistor types in use today: the MOS transistor in Chapter 5 and the bipolar transistor

in Chapter 6. These two chapters have been written to be completely independent of one

another and thus can be studied in either order as desired. Furthermore, the two chapters have the same structure, making it easier and faster to study the second device, as

well as to draw comparisons between the two device types.

After the study of Part I, the reader will be fully prepared to undertake the study of

either integrated-circuit amplifiers in Part II or digital integrated circuits in Part III.

3

CHAPTER 1

Signals

and Amplifiers

Introduction 5

1.5

Circuit Models for Amplifiers 21

1.1

Signals 6

1.6

Frequency Response of Amplifiers 30

1.2

Frequency Spectrum of Signals 9

Summary 41

1.3

Analog and Digital Signals 11

Problems 42

1.4 Amplifiers 14

IN THIS CHAPTER YOU WILL LEARN

1. That electronic circuits process signals, and thus understanding electrical signals is essential to appreciating the material in this book.

2. The ThÃ©venin and Norton representations of signal sources.

3. The representation of a signal as the sum of sine waves.

4. The analog and digital representations of a signal.

5. The most basic and pervasive signal-processing function: signal amplification, and correspondingly, the signal amplifier.

6. How amplifiers are characterized (modeled) as circuit building blocks

independent of their internal circuitry.

7. How the frequency response of an amplifier is measured, and how it is

calculated, especially in the simple but common case of a single-timeconstant (STC) type response.

Introduction

The subject of this book is modern electronics, a field that has come to be known as microelectronics. Microelectronics refers to the integrated-circuit (IC) technology that at the

time of this writing is capable of producing circuits that contain hundreds of millions of

components in a small piece of silicon (known as a silicon chip) whose area is on the order

of 100 mm2. One such microelectronic circuit, for example, is a complete digital computer,

which accordingly is known as a microcomputer or, more generally, a microprocessor.

In this book we shall study electronic devices that can be used singly (in the design of discrete circuits) or as components of an integrated-circuit (IC) chip. We shall study the

design and analysis of interconnections of these devices, which form discrete and integrated

circuits of varying complexity and perform a wide variety of functions. We shall also learn

about available IC chips and their application in the design of electronic systems.

The purpose of this first chapter is to introduce some basic concepts and terminology. In

particular, we shall learn about signals and about one of the most important signal-processing

functions electronic circuits are designed to perform, namely, signal amplification. We shall

then look at circuit representations or models for linear amplifiers. These models will be

employed in subsequent chapters in the design and analysis of actual amplifier circuits.

5

6 Chapter 1 Signals and Amplifiers

In addition to motivating the study of electronics, this chapter serves as a bridge between

the study of linear circuits and that of the subject of this book: the design and analysis of

electronic circuits.

1.1 Signals

Signals contain information about a variety of things and activities in our physical world.

Examples abound: Information about the weather is contained in signals that represent the

air temperature, pressure, wind speed, etc. The voice of a radio announcer reading the news

into a microphone provides an acoustic signal that contains information about world affairs.

To monitor the status of a nuclear reactor, instruments are used to measure a multitude of

relevant parameters, each instrument producing a signal.

To extract required information from a set of signals, the observer (be it a human or a

machine) invariably needs to process the signals in some predetermined manner. This signal

processing is usually most conveniently performed by electronic systems. For this to be possible, however, the signal must first be converted into an electrical signal, that is, a voltage or a

current. This process is accomplished by devices known as transducers. A variety of transducers exist, each suitable for one of the various forms of physical signals. For instance, the

sound waves generated by a human can be converted into electrical signals by using a microphone, which is in effect a pressure transducer. It is not our purpose here to study transducers;

rather, we shall assume that the signals of interest already exist in the electrical domain and

represent them by one of the two equivalent forms shown in Fig. 1.1. In Fig. 1.1(a) the signal is

represented by a voltage source vs(t) having a source resistance Rs. In the alternate representation of Fig. 1.1(b) the signal is represented by a current source is(t) having a source resistance

Rs. Although the two representations are equivalent, that in Fig. 1.1(a) (known as the ThÃ©venin

form) is preferred when Rs is low. The representation of Fig. 1.1(b) (known as the Norton

form) is preferred when Rs is high. The reader will come to appreciate this point later in this

chapter when we study the different types of amplifiers. For the time being, it is important to

be familiar with ThÃ©veninâ€™s and Nortonâ€™s theorems (for a brief review, see Appendix D) and to

note that for the two representations in Fig. 1.1 to be equivalent, their parameters are related by

vs ( t ) = Rs is ( t )

Rs

vs(t)

(a)

is(t)

Rs

(b)

Figure 1.1 Two alternative representations of

a signal source: (a) the ThÃ©venin form; (b) the

Norton form.

Example 1.1

The output resistance of a signal source, although inevitable, is an imperfection that limits the ability of the

source to deliver its full signal strength to a load. To see this point more clearly, consider the signal source

when connected to a load resistance RL as shown in Fig. 1.2. For the case in which the source is represented

1.1 Signals

by its ThÃ©venin equivalent form, find the voltage vo that appears across RL, and hence the condition that Rs

must satisfy for vo to be close to the value of vs. Repeat for the Norton-represented source; in this case

finding the current io that flows through RL and hence the condition that Rs must satisfy for io to be close to

the value of is.

Rs

io

vs

RL

vo

is

Rs

RL

(a)

(b)

Figure 1.2 Circuits for

Example 1.1.

Solution

For the ThÃ©venin-represented signal source shown in Fig. 1.2(a), the output voltage vo that appears across

the load resistance RL can be found from the ratio of the voltage divider formed by Rs and RL,

RL

v o = v s ----------------RL + Rs

From this equation we see that for

vo vs

the source resistance Rs must be much lower than the load resistance RL,

Rs RL

Thus, for a source represented by its ThÃ©venin equivalent, ideally Rs = 0, and as Rs is increased, relative to

the load resistance RL with which this source is intended to operate, the voltage vo that appears across the

load becomes smaller, not a desirable outcome.

Next, we consider the Norton-represented signal source in Fig. 1.2(b). To obtain the current io that flows

through the load resistance RL, we utilize the ratio of the current divider formed by Rs and RL,

Rs

i o = i s ----------------Rs + RL

From this relationship we see that for

io is

the source resistance Rs must be much larger that RL,

Rs RL

Thus for a signal source represented by its Norton equivalent, ideally Rs = âˆž, and as Rs is reduced, relative

to the load resistance RL with which this source is intended to operate, the current io that flows through the

load becomes smaller, not a desirable outcome.

Finally, we note that although circuit designers cannot usually do much about the value of Rs; they may

have to devise a circuit solution that minimizes or eliminates the loss of signal strength that results when

the source is connected to the load.

7

8 Chapter 1 Signals and Amplifiers

EXERCISES

1.1 For the signal-source representations shown in Figs. 1.1(a) and 1.1(b), what are the open-circuit

output voltages that would be observed? If, for each, the output terminals are short-circuited (i.e.,

wired together), what current would flow? For the representations to be equivalent, what must the relationship be between vs, is, and Rs?

Ans. For (a), voc = vs(t); for (b), voc = Rsis(t); for (a), i sc = v s ( t ) â„ R s ; for (b), isc = is(t); for equivalency,

vs(t) = Rsis(t)

1.2 A signal source has an open-circuit voltage of 10 mV and a short-circuit current of 10 Î¼A. What is the

source resistance?

Ans. 1 kÎ©

1.3 A signal source that is most conveniently represented by its ThÃ©venin equivalent has vs = 10 mV and

Rs = 1 kÎ©. If the source feeds a load resistance RL, find the voltage vo that appears across the load for

RL = 100 kÎ©, 10 kÎ©, 1 kÎ©, and 100 Î©. Also, find the lowest permissible value of RL for which the

output voltage is at least 80% of the source voltage.

Ans. 9.9 mV; 9.1 mV; 5 mV; 0.9 mV; 4 kÎ©

1.4 A signal source that is most conveniently represented by its Norton equivalent form has is = 10 Î¼A

and Rs = 100 kÎ©. If the source feeds a load resistance RL, find the current io that flows through the load

for RL = 1 kÎ©, 10 kÎ©, 100 kÎ©, and 1 MÎ©. Also, find the largest permissible value of RL for which the

load current is at least 80% of the source current.

Ans. 9.9 Î¼A; 9.1 Î¼A; 5 Î¼A; 0.9 Î¼A; 25 kÎ©

From the discussion above, it should be apparent that a signal is a time-varying quantity that

can be represented by a graph such as that shown in Fig. 1.3. In fact, the information content of

the signal is represented by the changes in its magnitude as time progresses; that is, the information

is contained in the â€œwigglesâ€ in the signal waveform. In general, such waveforms are difficult to

characterize mathematically. In other words, it is not easy to describe succinctly an arbitrarylooking waveform such as that of Fig. 1.3. Of course, such a description is of great importance for

the purpose of designing appropriate signal-processing circuits that perform desired functions on

the given signal. An effective approach to signal characterization is studied in the next section.

Figure 1.3 An arbitrary voltage signal vs (t).

1.2 Frequency Spectrum of Signals 9

1.2 Frequency Spectrum of Signals

An extremely useful characterization of a signal, and for that matter of any arbitrary function

of time, is in terms of its frequency spectrum. Such a description of signals is obtained

through the mathematical tools of Fourier series and Fourier transform.1 We are not interested here in the details of these transformations; suffice it to say that they provide the means

for representing a voltage signal vs(t) or a current signal is(t) as the sum of sine-wave signals

of different frequencies and amplitudes. This makes the sine wave a very important signal in

the analysis, design, and testing of electronic circuits. Therefore, we shall briefly review the

properties of the sinusoid.

Figure 1.4 shows a sine-wave voltage signal va(t),

v a ( t ) = V a sin Ï‰ t

(1.1)

where Va denotes the peak value or amplitude in volts and Ï‰ denotes the angular frequency in

radians per second; that is, Ï‰ = 2 Ï€ f rad/s, where f is the frequency in hertz, f = 1/T Hz, and

T is the period in seconds.

The sine-wave signal is completely characterized by its peak value Va , its frequency Ï‰,

and its phase with respect to an arbitrary reference time. In the case depicted in Fig. 1.4, the

time origin has been chosen so that the phase angle is 0. It should be mentioned that it is common to express the amplitude of a sine-wave signal in terms of its root-mean-square (rms)

value, which is equal to the peak value divided by 2. Thus the rms value of the sinusoid va(t)

of Fig. 1.4 is Va â„ 2. For instance, when we speak of the wall power supply in our homes as

being 120 V, we mean that it has a sine waveform of 120 2 volts peak value.

Returning now to the representation of signals as the sum of sinusoids, we note that the Fourier series is utilized to accomplish this task for the special case of a signal that is a periodic function of time. On the other hand, the Fourier transform is more general and can be used to obtain

the frequency spectrum of a signal whose waveform is an arbitrary function of time.

The Fourier series allows us to express a given periodic function of time as the sum of an

infinite number of sinusoids whose frequencies are harmonically related. For instance, the

symmetrical square-wave signal in Fig. 1.5 can be expressed as

4V

v ( t ) = ------- (sin Ï‰ 0 t + --13- sin 3 Ï‰ 0 t + --15- sin 5 Ï‰ 0 t + . . . )

Ï€

(1.2)

Figure 1.4 Sine-wave voltage signal of

amplitude Va and frequency f = 1/T Hz. The

angular frequency Ï‰ = 2Ï€ f rad/s.

1

The reader who has not yet studied these topics should not be alarmed. No detailed application of this

material will be made until Chapter 9. Nevertheless, a general understanding of Section 1.2 should be

very helpful in studying early parts of this book.

10 Chapter 1 Signals and Amplifiers

Figure 1.5 A symmetrical square-wave signal of amplitude V.

where V is the amplitude of the square wave and Ï‰ 0 = 2 Ï€ â„ T (T is the period of the square

wave) is called the fundamental frequency. Note that because the amplitudes of the

harmonics progressively decrease, the infinite series can be truncated, with the truncated

series providing an approximation to the square waveform.

The sinusoidal components in the series of Eq. (1.2) constitute the frequency spectrum of

the square-wave signal. Such a spectrum can be graphically represented as in Fig. 1.6, where

the horizontal axis represents the angular frequency Ï‰ in radians per second.

The Fourier transform can be applied to a nonperiodic function of time, such as that

depicted in Fig. 1.3, and provides its frequency spectrum as a continuous function of frequency, as indicated in Fig. 1.7. Unlike the case of periodic signals, where the spectrum consists of discrete frequencies (at Ï‰ 0 and its harmonics), the spectrum of a nonperiodic signal

contains in general all possible frequencies. Nevertheless, the essential parts of the spectra

of practical signals are usually confined to relatively short segments of the frequency (Ï‰)

axisâ€”an observation that is very useful in the processing of such signals. For instance, the

spectrum of audible sounds such as speech and music extends from about 20 Hz to about

20 kHzâ€”a frequency range known as the audio band. Here we should note that although

some musical tones have frequencies above 20 kHz, the human ear is incapable of hearing

frequencies that are much above 20 kHz. As another example, analog video signals have

their spectra in the range of 0 MHz to 4.5 MHz.

Figure 1.6 The frequency spectrum (also known as the line spectrum) of the periodic

square wave of Fig. 1.5.

1.3 Analog and Digital Signals 11

Figure 1.7 The frequency spectrum of

an arbitrary waveform such as that in Fig.

1.3.

We conclude this section by noting that a signal can be represented either by the manner in

which its waveform varies with time, as for the voltage signal va(t) shown in Fig. 1.3, or in

terms of its frequency spectrum, as in Fig. 1.7. The two alternative representations are known

as the time-domain representation and the frequency-domain representation, respectively. The

frequency-domain representation of va(t) will be denoted by the symbol Va(Ï‰).

EXERCISES

1.5 Find the frequencies f and Ï‰ of a sine-wave signal with a period of 1 ms.

3

Ans. f = 1000 Hz; Ï‰ = 2 Ï€ Ã— 10 rad/s

1.6 What is the period T of sine waveforms characterized by frequencies of (a) f = 60 Hz? (b) f = 10âˆ’3 Hz?

(c) f = 1 MHz?

Ans. 16.7 ms; 1000 s; 1 Î¼s

1.7 The UHF (ultra high frequency) television broadcast band begins with channel 14 and extends from

470 MHz to 806 MHz. If 6 MHz is allocated for each channel, how many channels can this band

accommodate?

Ans. 56; channels 14 to 69

1.8 When the square-wave signal of Fig. 1.5, whose Fourier series is given in Eq. (1.2), is applied to a resisT

tor, the total power dissipated may be calculated directly using the relationship P = 1 â„ T âˆ« 0 ( v 2 â„ R ) dt

or indirectly by summing the contribution of each of the harmonic components, that is, P = P1 + P3 +

P5 + â€¦, which may be found directly from rms values. Verify that the two approaches are equivalent.

What fraction of the energy of a square wave is in its fundamental? In its first five harmonics? In its first

seven? First nine? In what number of harmonics is 90% of the energy? (Note that in counting harmonics,

the fundamental at Ï‰ 0 is the first, the one at 2Ï‰ 0 is the second, etc.)

Ans. 0.81; 0.93; 0.95; 0.96; 3

1.3 Analog and Digital Signals

The voltage signal depicted in Fig. 1.3 is called an analog signal. The name derives from

the fact that such a signal is analogous to the physical signal that it represents. The magnitude of an analog signal can take on any value; that is, the amplitude of an analog signal

exhibits a continuous variation over its range of activity. The vast majority of signals in the

12 Chapter 1 Signals and Amplifiers

world around us are analog. Electronic circuits that process such signals are known as analog circuits. A variety of analog circuits will be studied in this book.

An alternative form of signal representation is that of a sequence of numbers, each number representing the signal magnitude at an instant of time. The resulting signal is called a

digital signal. To see how a signal can be represented in this formâ€”that is, how signals can

be converted from analog to digital formâ€”consider Fig. 1.8(a). Here the curve represents a

voltage signal, identical to that in Fig. 1.3. At equal intervals along the time axis, we have

marked the time instants t0, t1, t2, and so on. At each of these time instants, the magnitude of

the signal is measured, a process known as sampling. Figure 1.8(b) shows a representation

of the signal of Fig. 1.8(a) in terms of its samples. The signal of Fig. 1.8(b) is defined only at

the sampling instants; it no longer is a continuous function of time; rather, it is a discretetime signal. However, since the magnitude of each sample can take any value in a continuous

range, the signal in Fig. 1.8(b) is still an analog signal.

Now if we represent the magnitude of each of the signal samples in Fig. 1.8(b) by a number

having a finite number of digits, then the signal amplitude will no longer be continuous;

rather, it is said to be quantized, discretized, or digitized. The resulting digital signal then is

simply a sequence of numbers that represent the magnitudes of the successive signal samples.

The choice of number system to represent the signal samples affects the type of digital

signal produced, and has a profound effect on the complexity of the digital circuits required

to process the signals. It turns out that the binary number system results in the simplest possible digital signals and circuits. In a binary system, each digit in the number takes on one of

(a)

Figure 1.8 Sampling the continuous-time analog signal in (a) results in the discrete-time signal in (b).

1.3 Analog and Digital Signals 13

v (t)

5

Logic values

0

1

0

1

1

0

1

0

0

Time, t

Figure 1.9 Variation of a particular binary digital signal with time.

only two possible values, denoted 0 and 1. Correspondingly, the digital signals in binary systems need have only two voltage levels, which can be labeled low and high. As an example, in

some of the digital circuits studied in this book, the levels are 0 V and +5 V. Figure 1.9

shows the time variation of such a digital signal. Observe that the waveform is a pulse train

with 0 V representing a 0 signal, or logic 0, and +5 V representing logic 1.

If we use N binary digits (bits) to represent each sample of the analog signal, then the digitized sample value can be expressed as

0

1

2

Nâˆ’1

D = b 0 2 + b 1 2 + b 2 2 + â€¦ + b Nâˆ’1 2

(1.3)

where b0, b1, â€¦, bNâ€“1, denote the N bits and have values of 0 or 1. Here bit b0 is the least

significant bit (LSB), and bit bNâ€“1 is the most significant bit (MSB). Conventionally, this binary

number is written as bNâ€“1 bNâ€“2 â€¦ b0. We observe that such a representation quantizes the analog

sample into one of 2N levels. Obviously the greater the number of bits (i.e., the larger the N), the

closer the digital word D approximates the magnitude of the analog sample. That is, increasing

the number of bits reduces the quantization error and increases the resolution of the analog-todigital conversion. This improvement is, however, usually obtained at the expense of more complex and hence more costly circuit implementations. It is not our purpose here to delve into this

topic any deeper; we merely want the reader to appreciate the nature of analog and digital signals.

Nevertheless, it is an opportune time to introduce a very important circuit building block of modern electronic systems: the analog-to-digital converter (A/D or ADC) shown in block form in

Fig. 1.10 The ADC accepts at its input the samples of an analog signal and provides for each

input sample the corresponding N-bit digital representation (according to Eq. 1.3) at its N output

terminals. Thus although the voltage at the input might be, say, 6.51 V, at each of the output terminals (say, at the ith terminal), the voltage will be either low (0 V) or high (5 V) if bi is supposed

Analog

v

input A

A/D

converter

b0

b1

bN1

Digital

output

Figure 1.10 Block-diagram representation of the analog-to-digital converter (ADC).

14 Chapter 1 Signals and Amplifiers

to be 0 or 1, respectively. The dual circuit of the ADC is the digital-to-analog converter (D/A or

DAC). It converts an N-bit digital input to an analog output voltage.

Once the signal is in digital form, it can be processed using digital circuits. Of course

digital circuits can deal also with signals that do not have an analog origin, such as the signals that represent the various instructions of a digital computer.

Since digital circuits deal exclusively with binary signals, their design is simpler than that of

analog circuits. Furthermore, digital systems can be designed using a relatively few different

kinds of digital circuit blocks. However, a large number (e.g., hundreds of thousands or even millions) of each of these blocks are usually needed. Thus the design of digital circuits poses its own

set of challenges to the designer but provides reliable and economic implementations of a great

variety of signal-processing functions, many of which are not possible with analog circuits. At

the present time, more and more of the signal-processing functions are being performed digitally.

Examples around us abound: from the digital watch and the calculator to digital audio systems,

digital cameras and, more recently, digital television. Moreover, some longstanding analog systems such as the telephone communication system are now almost entirely digital. And we

should not forget the most important of all digital systems, the digital computer.

The basic building blocks of digital systems are logic circuits and memory circuits. We

shall study both in this book, beginning in Chapter 13.

One final remark: Although the digital processing of signals is at present all-pervasive,

there remain many signal-processing functions that are best performed by analog circuits.

Indeed, many electronic systems include both analog and digital parts. It follows that a good

electronics engineer must be proficient in the design of both analog and digital circuits, or

mixed-signal or mixed-mode design as it is currently known. Such is the aim of this book.

EXERCISE

1.9 Consider a 4-bit digital word D = b3b2b1b0 (see Eq. 1.3) used to represent an analog signal vA that varies

between 0 V and +15 V.

(a) Give D corresponding to vA = 0 V, 1 V, 2 V, and 15 V.

(b) What change in vA causes a change from 0 to 1 in (i) b0, (ii) b1, (iii) b2, and (iv) b3?

(c) If vA = 5.2 V, what do you expect D to be? What is the resulting error in representation?

Ans. (a) 0000, 0001, 0010, 1111; (b) +1 V, +2 V, +4 V, +8 V; (c) 0101, â€“4%

1.4 Amplifiers

In this section, we shall introduce the most fundamental signal-processing function, one that

is employed in some form in almost every electronic system, namely, signal amplification.

We shall study the amplifier as a circuit building-block; that is, we shall consider its external

characteristics and leave the design of its internal circuit to later chapters.

1.4.1 Signal Amplification

From a conceptual point of view the simplest signal-processing task is that of signal amplification. The need for amplification arises because transducers provide signals that are said to be

â€œweak,â€ that is, in the microvolt (Î¼V) or millivolt (mV) range and possessing little energy. Such

1.4 Amplifiers

signals are too small for reliable processing, and processing is much easier if the signal magnitude is made larger. The functional block that accomplishes this task is the signal amplifier.

It is appropriate at this point to discuss the need for linearity in amplifiers. Care must be

exercised in the amplification of a signal, so that the information contained in the signal is

not changed and no new information is introduced. Thus when we feed the signal shown in Fig.

1.3 to an amplifier, we want the output signal of the amplifier to be an exact replica of that at

the input, except of course for having larger magnitude. In other words, the â€œwigglesâ€ in the

output waveform must be identical to those in the input waveform. Any change in waveform

is considered to be distortion and is obviously undesirable.

An amplifier that preserves the details of the signal waveform is characterized by the relationship

vo ( t ) = A vi ( t )

(1.4)

where vi and vo are the input and output signals, respectively, and A is a constant representing

the magnitude of amplification, known as amplifier gain. Equation (1.4) is a linear relationship; hence the amplifier it describes is a linear amplifier. It should be easy to see that if the

relationship between vo and vi contains higher powers of vi, then the waveform of vo will no

longer be identical to that of vi. The amplifier is then said to exhibit nonlinear distortion.

The amplifiers discussed so far are primarily intended to operate on very small input signals.

Their purpose is to make the signal magnitude larger and therefore are thought of as voltage

amplifiers. The preamplifier in the home stereo system is an example of a voltage amplifier.

At this time we wish to mention another type of amplifier, namely, the power amplifier.

Such an amplifier may provide only a modest amount of voltage gain but substantial current

gain. Thus while absorbing little power from the input signal source to which it is connected,

often a preamplifier, it delivers large amounts of power to its load. An example is found in the

power amplifier of the home stereo system, whose purpose is to provide sufficient power to

drive the loudspeaker, which is the amplifier load. Here we should note that the loudspeaker is

the output transducer of the stereo system; it converts the electric output signal of the system

into an acoustic signal. A further appreciation of the need for linearity can be acquired by

reflecting on the power amplifier. A linear power amplifier causes both soft and loud music

passages to be reproduced without distortion.

1.4.2 Amplifier Circuit Symbol

The signal amplifier is obviously a two-port network. Its function is conveniently represented by

the circuit symbol of Fig. 1.11(a). This symbol clearly distinguishes the input and output ports

and indicates the direction of signal flow. Thus, in subsequent diagrams it will not be necessary

to label the two ports â€œinputâ€ and â€œoutput.â€ For generality we have shown the amplifier to have

two input terminals that are distinct from the two output terminals. A more common situation is

illustrated in Fig. 1.11(b), where a common terminal exists between the input and output ports of

the amplifier. This common terminal is used as a reference point and is called the circuit

ground.

1.4.3 Voltage Gain

A linear amplifier accepts an input signal vI (t) and provides at the output, across a load resistance RL (see Fig. 1.12(a)), an output signal vO(t) that is a magnified replica of vI (t). The

voltage gain of the amplifier is defined by

v

Voltage gain ( A v ) â‰¡ ----OvI

(1.5)

15

16 Chapter 1 Signals and Amplifiers

(a)

Figure 1.11 (a) Circuit symbol for amplifier. (b) An amplifier with a common terminal (ground) between

the input and output ports.

Fig. 1.12(b) shows the transfer characteristic of a linear amplifier. If we apply to the input

of this amplifier a sinusoidal voltage of amplitude VË† , we obtain at the output a sinusoid of

amplitude A vVË† .

1.4.4 Power Gain and Current Gain

An amplifier increases the signal power, an important feature that distinguishes an amplifier

from a transformer. In the case of a transformer, although the voltage delivered to the load

could be greater than the voltage feeding the input side (the primary), the power delivered to

the load (from the secondary side of the transformer) is less than or at most equal to the power

supplied by the signal source. On the other hand, an amplifier provides the load with power

greater than that obtained from the signal source. That is, amplifiers have power gain. The

power gain of the amplifier in Fig. 1.12(a) is defined as

load power ( P L )

Power gain ( Ap ) â‰¡ ---------------------------------------input power ( P I )

vO iO

= --------vI iI

(a)

Figure 1.12 (a) A voltage amplifier fed with a signal vI (t) and connected to a load resistance RL.

(b) Transfer characteristic of a linear voltage amplifier with voltage gain Av .

(1.6)

(1.7)

1.4 Amplifiers

where iO is the current that the amplifier delivers to the load (RL), iO = vO /RL, and iI is the current the amplifier draws from the signal source. The current gain of the amplifier is defined as

i

Current gain ( A i ) â‰¡ ---OiI

(1.8)

From Eqs. (1.5) to (1.8) we note that

A p = Av A i

(1.9)

1.4.5 Expressing Gain in Decibels

The amplifier gains defined above are ratios of similarly dimensioned quantities. Thus they

will be expressed either as dimensionless numbers or, for emphasis, as V/V for the voltage

gain, A/A for the current gain, and W/W for the power gain. Alternatively, for a number of

reasons, some of them historic, electronics engineers express amplifier gain with a logarithmic measure. Specifically the voltage gain Av can be expressed as

Voltage gain in decibels = 20 log Av

dB

and the current gain Ai can be expressed as

Current gain in decibels = 20 log A i

dB

Since power is related to voltage (or current) squared, the power gain Ap can be expressed in

decibels as

Power gain in decibels = 10 log A p

dB

The absolute values of the voltage and current gains are used because in some cases Av or

Ai will be a negative number. A negative gain Av simply means that there is a 180Â° phase difference between input and output signals; it does not imply that the amplifier is attenuating

the signal. On the other hand, an amplifier whose voltage gain is, say, â€“20 dB is in fact attenuating the input signal by a factor of 10 (i.e., Av = 0.1 V/V).

1.4.6 The Amplifier Power Supplies

Since the power delivered to the load is greater than the power drawn from the signal source,

the question arises as to the source of this additional power. The answer is found by observing that amplifiers need dc power supplies for their operation. These dc sources supply the

extra power delivered to the load as well as any power that might be dissipated in the internal circuit of the amplifier (such power is converted to heat). In Fig. 1.12(a) we have not

explicitly shown these dc sources.

Figure 1.13(a) shows an amplifier that requires two dc sources: one positive of value VCC

and one negative of value VEE. The amplifier has two terminals, labeled V + and V â€“, for connection to the dc supplies. For the amplifier to operate, the terminal labeled V + has to be connected to the positive side of a dc source whose voltage is VCC and whose negative side is

connected to the circuit ground. Also, the terminal labeled V â€“ has to be connected to the negative side of a dc source whose voltage is VEE and whose positive side is connected to the circuit

ground. Now, if the current drawn from the positive supply is denoted ICC and that from the

negative supply is IEE (see Fig. 1.13a), then the dc power delivered to the amplifier is

17

18 Chapter 1 Signals and Amplifiers

P dc = V CC I CC + V EE I EE

If the power dissipated in the amplifier circuit is denoted Pdissipated, the power-balance equation for the amplifier can be written as

P dc + P I = P L + P dissipated

where PI is the power drawn from the signal source and PL is the power delivered to the load.

Since the power drawn from the signal source is usually small, the amplifier power efficiency is defined as

P

Î· â‰¡ ------L- Ã— 100

P dc

(1.10)

The power efficiency is an important performance parameter for amplifiers that handle large

amounts of power. Such amplifiers, called power amplifiers, are used, for example, as output amplifiers of stereo systems.

In order to simplify circuit diagrams, we shall adopt the convention illustrated in Fig. 1.13(b).

Here the V + terminal is shown connected to an arrowhead pointing upward and the V â€“ terminal

to an arrowhead pointing downward. The corresponding voltage is indicated next to each arrowhead. Note that in many cases we will not explicitly show the connections of the amplifier to the

dc power sources. Finally, we note that some amplifiers require only one power supply.

ICC

VCC

ICC

VCC

IEE

IEE

(a)

VEE

VEE

(b)

Figure 1.13 An amplifier that requires two dc supplies (shown as batteries) for operation.

Example 1.2

Consider an amplifier operating from Â±10-V power supplies. It is fed with a sinusoidal voltage having 1 V

peak and delivers a sinusoidal voltage output of 9 V peak to a 1-kÎ© load. The amplifier draws a current of

9.5 mA from each of its two power supplies. The input current of the amplifier is found to be sinusoidal

with 0.1 mA peak. Find the voltage gain, the current gain, the power gain, the power drawn from the dc

supplies, the power dissipated in the amplifier, and the amplifier efficiency.

Solution

9

Av = --- = 9 V/V

1

1.4 Amplifiers 19

or

A v = 20 log 9 = 19.1 dB

9V

IË†o = -----------1 kÎ©

IË†

A i = ---o- =

IË†

i

= 9 mA

9-----= 90 A/A

0.1

or

A i = 20 log 90 = 39.1 dB

9 9

P L = V orms I o rms = ------- ------- = 40.5 mW

2 2

1 0.1

P I = V irms I irms = ------- ------- = 0.05 mW

2 2

PL

40.5

A p = ------ = ---------- = 810 W/W

PI

0.05

or

A p = 10 log 810 = 29.1 dB

P dc = 10 Ã— 9.5 + 10 Ã— 9.5 = 190 mW

P dissipated = P dc + P I â€“ P L

= 190 + 0.05 â€“ 40.5 = 149.6 mW

P

Î· = ------L- Ã— 100 = 21.3%

P dc

From the above example we observe that the amplifier converts some of the dc power it

draws from the power supplies to signal power that it delivers to the load.

1.4.7 Amplifier Saturation

Practically speaking, the amplifier transfer characteristic remains linear over only a limited

range of input and output voltages. For an amplifier operated from two power supplies the output voltage cannot exceed a specified positive limit and cannot decrease below a specified negative limit. The resulting transfer characteristic is shown in Fig. 1.14, with the positive and

negative saturation levels denoted L+ and Lâ€“ , respectively. Each of the two saturation levels is

usually within a fraction of a volt of the voltage of the corresponding power supply.

Obviously, in order to avoid distorting the output signal waveform, the input signal swing

must be kept within the linear range of operation,

L

L

----âˆ’- â‰¤ v I â‰¤ ----+Av

Av

In Fig. 1.14, which shows two input waveforms and the corresponding output waveforms,

the peaks of the larger waveform have been clipped off because of amplifier saturation.

20 Chapter 1 Signals and Amplifiers

Figure 1.14 An amplifier transfer characteristic that is linear except for output saturation.

1.4.8 Symbol Convention

At this point, we draw the readerâ€™s attention to the terminology we shall employ throughout

the book. To illustrate the terminology, Fig. 1.15 shows the waveform of a current iC (t) that

is flowing through a branch in a particular circuit. The current iC (t) consists of a dc component IC on which is superimposed a sinusoidal component ic(t) whose peak amplitude is Ic.

Observe that at a time t, the total instantaneous current iC (t) is the sum of the dc current IC

and the signal current i c ( t ) ,

iC ( t ) = IC + ic ( t )

(1.11)

where the signal current is given by

i c ( t ) = I c sin Ï‰t

Thus, we state some conventions: Total instantaneous quantities are denoted by a lowercase

symbol with uppercase subscript(s), for example, iC (t), vDS (t). Direct-current (dc) quantities are

denoted by an uppercase symbol with uppercase subscript(s), for example IC , VDS . Incremental

1.5 Circuit Models for Amplifiers 21

iC

ic

Ic

iC

IC

0

t

Figure 1.15 Symbol convention employed throughout the book.

signal quantities are denoted by a lowercase symbol with lowercase subscript(s), for example,

ic(t), vgs(t). If the signal is a sine wave, then its amplitude is denoted by an uppercase symbol

with lowercase subscript(s), for example Ic , Vgs. Finally, although not shown in Fig. 1.15, dc

power supplies are denoted by an uppercase letter with a double-letter uppercase subscript, for

example, VCC , VDD. A similar notation is used for the dc current drawn from the power supply,

for example, ICC , IDD.

EXERCISES

1.10 An amplifier has a voltage gain of 100 V/V and a current gain of 1000 A/A. Express the voltage and

current gains in decibels and find the power gain.

Ans. 40 dB; 60 dB; 50 dB

1.11 An amplifier operating from a single 15-V supply provides a 12-V peak-to-peak sine-wave signal

to a 1-kÎ© load and draws negligible input current from the signal source. The dc current drawn from the

15-V supply is 8 mA. What is the power dissipated in the amplifier, and what is the amplifier efficiency?

Ans. 102 mW; 15%

1.5 Circuit Models for Amplifiers

A substantial part of this book is concerned with the design of amplifier circuits that use transistors of various types. Such circuits will vary in complexity from those using a single transistor to

those with 20 or more devices. In order to be able to apply the resulting amplifier circuit as a

building block in a system, one must be able to characterize, or model, its terminal behavior. In

this section, we study simple but effective amplifier models. These models apply irrespective of

the complexity of the internal circuit of the amplifier. The values of the model parameters can be

found either by analyzing the amplifier circuit or by performing measurements at the amplifier

terminals.