Electronic Devices and Circuits I.J. Nagrath
Electronic Devices and Circuits I.J. NAGRATH Adjunct Professor Former Deputy Director Birla Institute of Technology & Science Pilani New Delhi-110001 2012
ELECTRONIC DEVICES AND CIRCUITS I.J. Nagrath 2007 by PHI Learning Private Limited, New Delhi. All rights reserved. No part of this book may be reproduced in any form, by mimeograph or any other means, without permission in writing from the publisher. ISBN-978-81-203-3195-2 The export rights of this book are vested solely with the publisher. Sixth Printing º º º October, 2012 Published by Asoke K. Ghosh, PHI Learning Private Limited, M-97, Connaught Circus, New Delhi-110001 and Printed by Rajkamal Electric Press, Plot No. 2, Phase IV, HSIDC, Kundli-131028, Sonepat, Haryana.
Contents Preface ix 1. Semiconductors, Diodes and Diode Circuits 1 77 1.1 Introduction to Electronics 1 1.2 Typical Electronic Systems 1 1.3 Classification of Electronic Systems and Devices 3 1.4 The Future 4 1.5 Conduction in Solids 4 1.6 Doped Semiconductors 9 1.7 Junction Diodes 14 1.8 DC Analysis of Diode Circuits 20 1.9 Zener Diode as Voltage Regulator 23 1.10 Diode Circuits with Time-Varying Sources 23 1.11 Transition and Diffusion Capacitances 26 1.12 Switching Characteristics of a Diode 27 1.13 Special Purpose Diodes 28 1.14 Rectifiers and Power Supplies 38 1.15 Filters 48 1.16 Some Diode Wave Shaping Circuits 56 1.17 Additional Examples 61 Problems 72 2. Transistors and Other Devices 78 131 2.1 Introduction 78 2.2 Bipolar Junction Transistor (BJT) 80 2.3 Junction Field Effect Transistor (JFET) and Metal Oxide Semiconductor Field Effect Transistor (MOSFET) 94 iii
iv Contents 2.4 Manufacturing Integrated Devices and Circuits 107 2.5 Four-Layer Devices Thyristors 107 2.6 Additional Examples 114 Problems 125 3. Small-Signal Models, Amplification and Biasing 132 208 3.1 Introduction 132 3.2 Small-Signal Transistor Models 133 3.3 Hybrid-p Model 141 3.4 h-parameter Model 142 3.5 Transistor Biasing 150 3.6 Constant Current and Current Mirror Circuits 163 3.7 Bias Design, AC Gain, Input Output Impedances 168 3.8 Some Special Circuits 172 3.9 Darlington Pair 180 3.10 Feedback Pair 183 3.11 Emitter Coupled Pair 186 3.12 CMOS Circuits 189 3.13 Additional Examples 191 Problems 203 4. Small-Signal Amplifiers Frequency Response 209 275 4.1 Introduction 209 4.2 Single-Stage RC-Coupled Amplifier 213 4.3 Frequency Response 218 4.4 Tuned Amplifier 241 4.5 Gain Bandwidth Product 246 4.6 Multistage Amplifiers 249 4.7 Cascode Amplifier (CE-CB Configuration) 251 4.8 Additional Examples 256 Problems 269 5. Large-Signal Amplifiers 276 319 5.1 Amplifier Classes 276 5.2 Class-A Power Amplifiers 278 5.3 Transformer-Coupled Power Amplifier 287 5.4 Class-B Power Amplifiers 292 5.5 Complementary Symmetry Circuits 298 5.6 Distortion in Amplifiers 301 5.7 Class-AB Amplifiers 306 5.8 Class-C Power Amplifiers 306
Contents v 5.9 New Power Transistors 309 5.10 Additional Examples 314 Problems 318 6. Feedback Amplifiers and Oscillators 320 357 6.1 Feedback Concepts 320 6.2 Types of Feedback Circuits 321 6.3 Block Diagram Representation of Feedback Amplifiers 323 6.4 Effect of Feedback on Impedances 324 6.5 Some Negative Feedback Circuits 326 6.6 Properties of Negative Feedback 330 6.7 Stability in Feedback Amplifiers 334 6.8 Oscillator Operation 334 6.9 Phase Shift Oscillator 335 6.10 Wein Bridge Oscillator 338 6.11 Tuned Oscillators 339 6.12 Crystal Oscillators 342 6.13 Unijunction Oscillator 343 6.14 Phase-Locked Loop (PLL) 348 6.15 Additional Examples 350 Problems 354 7. Operational Amplifiers 358 409 7.1 Introduction 358 7.2 Basic Operational Amplifier 358 7.3 Differential Amplifier 365 7.4 Basic Operational Amplifier Circuit 372 7.5 Applications of OPAMPs 375 7.6 Linear Applications of OPAMPs 376 7.7 OPAMP Filters (Active Filters) 384 7.8 Nonlinear Applications of OPAMPs 391 7.9 Analog Simulation 397 7.10 Additional Examples 400 Problems 405 8. Multivibrators and Switching Regulators 410 444 8.1 Multivibrators 410 8.2 Analog Multivibrators 416 8.3 555 Timer 421 8.4 Power Supplies and Regulators 429 Problems 442
vi Contents 9. Integrated Circuits Fabrication 445 473 9.1 Introduction 445 9.2 Pre-Fabrication Stage 446 9.3 IC Fabrication 446 9.4 The Planar Processes 447 9.5 Illustration A Simple IC Fabrication 453 9.6 Monolithic Transistors Bipolar 455 9.7 Fabrication of MOSFET 459 9.8 Monolithic Diodes 461 9.9 Integrated Resistors 462 9.10 Integrated Capacitors 465 9.11 Metal Semiconductor Contact 466 9.12 Characteristics of IC Components 468 9.13 Monolithic Circuit Layout 468 9.14 Levels of Integration 469 Problems 472 10. Circuit Theory 474 520 10.1 Introduction 474 10.2 Voltage and Current Sources 474 10.3 Resistance 476 10.4 The Basic Laws of Electric Circuits 476 10.5 Resistances in Series and Parallel 478 10.6 General Methods of Network Analysis 480 10.7 Network Theorems 484 10.8 Step Response of RC Circuits 487 10.9 Duality of Networks 492 10.10 Sinusoidal Steady-State Circuit Analysis 493 10.11 Resonance 502 10.12 Miller s Theorem 504 10.13 Two-Port Networks 505 10.14 Frequency Response 512 Problems 516 11. Cathode Ray Oscilloscope (CRO) 521 534 11.1 Introduction 521 11.2 Cathode Ray Tube 521 11.3 CRO Applications 530
Contents vii Appendix The Ebers-Moll Model of the BJT 535 539 References 541 542 Answers to Problems 543 548 Index 549 554
Preface This book is designed to be course-specific for the undergraduate students pursuing courses in Electronics and Electrical Engineering and its related disciplines. The topics are presented to meet the standards and syllabi of various universities. The background material required for the study of the characteristics and applications of the electronic devices and circuits is covered in the first chapter. It includes introduction to semiconductors both intrinsic and doped (extrinsic) the concept of electrons and holes, drift and diffusion currents and pn-junction behaviour. The devices treated in Chapter 2 are diodes (including special purpose diodes), transistors BJTs, JFETs, and MOSFETs and also fourlayered devices, i.e. thyristors. These chapters acquaint the students with theory, characteristics, and construction of the electronic devices covered. Chapter 3 contains the presentation of smallsignal modelling of transistors, dc biasing of transistors, and some special circuits. The circuitry and analysis of small signal amplifiers, power amplifiers, feedback amplifiers, and oscillators are covered in Chapters 4 6. The circuits of both types of transistors are treated together in each of these chapters. Operational amplifiers and their parameters, differential amplifiers, and their linear and nonlinear applications form the contents of Chapter 7. Special circuits (multivibrators and switching regulators) and compound configurations of various kinds find a detailed treatment in Chapter 8. Chapter 9 is devoted to IC fabrication technology. A short but comprehensive presentation on circuit theory is offered in Chapter 10, primarily for quick reference or for teaching purposes where it forms part of the courseware. Finally, the concluding Chapter 11 offers a brief treatment of Cathode Ray Oscilloscope, so often required for practical measurements. The treatment of the topics throughout is succinct, to the point, yet well-explained and rigorous. The author acknowledges with thanks the efforts of the editorial and production teams of Prentice-Hall of India towards bringing out this book in excellent form. The feedback from the readers towards improvement of the book will be gratefully acknowledged by the author. I.J. NAGRATH ix
1 Semiconductors, Diodes and Diode Circuits 1.1 INTRODUCTION TO ELECTRONICS Electronics is a very wide field embracing almost all walks of human endeavour. In a way, electronics is the branch of electrical engineering which employs devices in which current flow is due to the controlled flow of charge carriers in a gas, in vacuum or in semiconductors. Electronic devices came into existence in the beginning of twentieth century. These devices used gaseous or vacuum medium for the flow of negatively charged particles, electrons. These devices were widely used for communications, controls and computers. A major breakthrough was achieved in the field of electronics when it became possible to use semiconductors such as silicon and germanium for making electronic devices. The semiconductor devices are smaller, cheaper, more reliable and consume less power than the vacuum or the gaseous devices. Further developments in the semiconductor technology made it possible to integrate a large number of devices in a small silicon chip, known as Integrated Circuit (IC). Today, the number of devices on a chip has gone well beyond ten million. The integrated circuits have revolutionized the field of electronics and it will not be unrealistic to call the present age as the electronics age. The impact of developments in electronics can be gauged from the availability of personal computers, which have tremendous capabilities as compared to computers in 1950s and 1960s, which occupied large space, consumed large power and costed millions of dollars. The major areas of application of electronics are communication, controls and computers, although it has invaded almost every field in our modern living. 1.2 TYPICAL ELECTRONIC SYSTEMS As human beings, we are interested in communicating with people around us. If the persons with whom we want to have communication are closeby, such as in a small classroom, we can 1
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