Fundamentals of RF and Microwave Transistor Amplifiers

Transcription

1 Fundamentals of RF and Microwave Transistor Amplifiers Inder J. Bahl A John Wiley & Sons, Inc., Publication

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3 Fundamentals of RF and Microwave Transistor Amplifiers

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5 Fundamentals of RF and Microwave Transistor Amplifiers Inder J. Bahl A John Wiley & Sons, Inc., Publication

6 Copyright 2009 by John Wiley & Sons, Inc. All rights reserved. Published by John Wiley & Sons, Inc., Hoboken, New Jersey Published simultaneously in Canada. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Sections 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, (978) , fax (978) , or on the web at Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) , fax (201) , or online at Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives or written sales materials. The advice and strategies contained herein may not be suitable for your situation. You should consult with a professional where appropriate. Neither the publisher nor author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages. For general information on our other products and services or for technical support, please contact our Customer Care Department within the United States at (800) , outside the United States at (317) or fax (317) Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic formats. For more information about Wiley products, visit our web site at Library of Congress Cataloging-in-Publication Data: Bahl,I.J. Fundamentals of RF and Microwave Transistor Amplifiers / Inder Bahl. p. cm. Includes bibliographical references and index. ISBN (cloth) 1. Amplifiers, Radio frequency. 2. Microwave amplifiers. 3. Transistor amplifiers. I. Title. TK6565.A55B dc Printed in the United States of America

7 Contents in Brief 1. Introduction 1 2. Linear Network Analysis Amplifier Characteristics and Definitions Transistors Transistor Models Matching Network Components Impedance Matching Techniques Amplifier Classes and Analyses Amplifier Design Methods High-Efficiency Amplifier Techniques Broadband Amplifier Techniques Linearization Techniques High-Voltage Power Amplifier Design Hybrid Amplifiers Monolithic Amplifiers Thermal Design Stability Analysis Biasing Networks Power Combining Integrated Function Amplifiers Amplifier Packages Transistor and Amplifier Measurements 613

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9 Contents Foreword Preface xvii xix 1. Introduction Transistor Amplifier Early History of Transistor Amplifiers Benefits of Transistor Amplifiers Transistors Design of Amplifiers Amplifier Manufacturing Technologies Applications of Amplifiers Amplifier Cost Current Trends Book Organization 13 References Linear Network Analysis Impedance Matrix Admittance Matrix ABCD Parameters S-Parameters S-Parameters for a One-Port Network Relationships Between Various Two-Port Parameters 29 References 31 Problems Amplifier Characteristics and Definitions Bandwidth Power Gain Input and Output VSWR Output Power Power Added Efficiency Intermodulation Distortion IP ACPR EVM Harmonic Power 43

10 viii CONTENTS 3.8. Peak-to-Average Ratio Combiner Efficiency Noise Characterization Noise Figure Noise Temperature Noise Bandwidth Optimum Noise Match Constant Noise Figure and Gain Circles Simultaneous Input and Noise Match Dynamic Range Multistage Amplifier Characteristics Multistage IP Multistage PAE Multistage NF Gate and Drain Pushing Factors Amplifier Temperature Coefficient Mean Time to Failure 58 References 59 Problems Transistors Transistor Types Silicon Bipolar Transistor Figure of Merit High-Frequency Noise Performance of Silicon BJT Power Performance GaAs MESFET Small-Signal Equivalent Circuit Figure of Merit High-Frequency Noise Properties of MESFETs Heterojunction Field Effect Transistor High-Frequency Noise Properties of HEMTs Indium Phosphide phemts Heterojunction Bipolar Transistors High-Frequency Noise Properties of HBTs SiGe Heterojunction Bipolar Transistors MOSFET 86 References 88 Problems Transistor Models Transistor Model Types Physics/Electromagnetic Theory Based Models Analytical or Hybrid Models Measurement Based Models MESFET Models Linear Models Nonlinear Models phemt Models Linear Models 105

11 CONTENTS ix Nonlinear Models HBT Model MOSFET Models BJT Models Transistor Model Scaling Source-Pull and Load-Pull Data Theoretical Load-Pull Data Measured Power and PAE Source Pull and Load Pull Measured IP3 Source and Load Impedance Source and Load Impedance Scaling Temperature-Dependent Models 120 References 121 Problems Matching Network Components Impedance Matching Elements Transmission Line Matching Elements Microstrip Coplanar Lines Lumped Elements Capacitors Inductors Resistors Bond Wire Inductors Single Wire Ground Plane Effect Multiple Wires Maximum Current Handling of Wire Broadband Inductors 145 References 147 Problems Impedance Matching Techniques One-Port and Two-Port Networks Narrowband Matching Techniques Lumped-Element Matching Techniques Transmission Line Matching Techniques WideBand Matching Techniques Gain Bandwidth Limitations Lumped-Element Wideband Matching Techniques Transmission Line Wideband Matching Networks Balun-Type Wideband Matching Techniques Bridged-T Matching Network 180 References 182 Problems Amplifier Classes and Analyses Classes of Amplifiers Analysis of Class-A Amplifiers 188

12 x CONTENTS 8.3. Analysis of Class-B Amplifiers Single-Ended Class-B Amplifier Push Pull Class-B Amplifier Overdriven Class-B Amplifier Analysis of Class-C Amplifiers Analysis of Class-E Amplifiers Analysis of Class-F Amplifiers Comparison of Various Amplifier Classes 204 References 207 Problems Amplifier Design Methods Amplifier Design Transistor Type and Fabrication Technology Transistor Size Selection Design Method Circuit Topology Circuit Analysis and Optimization Stability and Thermal Analyses Amplifier Design Techniques Load-Line Method Low Loss Match Design Technique Nonlinear Design Method Taguchi Experimental Method Matching Networks Reactive/Resistive Cluster Matching Technique Amplifier Design Examples Low-Noise Amplifier Design Maximum Gain Amplifier Design Power Amplifier Design Multistage Driver Amplifier Design GaAs HBT Power Amplifer Silicon Based Amplifier Design Si IC LNA Si IC Power Amplifiers 249 References 255 Problems High-Efficiency Amplifier Techniques High-Efficiency Design Overdriven Amplifier Design Class-B Amplifier Design Class-E Amplifier Design Class-F Amplifier Design Harmonic Reaction Amplifier Harmonic Injection Technique Harmonic Control Amplifier High-PAE Design Considerations 284

13 CONTENTS xi Harmonic Tuning Bench Matching Network Loss Calculation Matching Network Loss Reduction 289 References 290 Problems Broadband Amplifier Techniques Transistor Bandwidth Limitations Transistor Gain Roll-off Variable Device Input and Output Impedance Power Bandwidth Product Broadband Amplifier Techniques Reactive/Resistive Topology Feedback Amplifiers Balanced Amplifiers Distributed Amplifiers Active Matching Broadband Technique Cascode Configuration Comparison of Broadband Techniques Broadband Power Amplifier Design Considerations Topology Selection Device Aspect Ratio Low-Loss Matching Networks Gain Flatness Technique Harmonic Termination Thermal Design 327 References 328 Problems Linearization Techniques Nonlinear Analysis Single-Tone Analysis Two-Tone Analysis Phase Distortion Linearization of Power Amplifiers Pulsed-Doped Devices and Optimum Match Predistortion Techniques Feedforward Technique Efficiency Enhancement Techniques for Linear Amplifiers Chireix Outphasing Doherty Amplifier Envelope Elimination and Restoration Bias Adaptation Linear Amplifier Design Considerations Amplifier Gain Minimum Source and Load Mismatch Linear Amplifier Design Examples 350 References 358 Problems 361

14 xii CONTENTS 13. High-Voltage Power Amplifier Design Performance Overview of High-Voltage Transistors Advantages Applications High-Voltage Transistors Si Bipolar Junction Transistors Si LDMOS Transistors GaAs FieldPlate MESFETs GaAs FieldPlate phemts GaAs HBTs SiC MESFET SiC GaN HEMTs High-Power Amplifier Design Considerations Thermal Design of Active Devices Power Handling of Passive Components Power Amplifier Design Examples HV Hybrid Amplifiers HV Monolithic Amplifiers Broadband HV Amplifiers Series FET Amplifiers 390 References 394 Problems Hybrid Amplifiers Hybrid Amplifier Technologies Printed Circuit Boards Hybrid Integrated Circuits Thin-Film MIC Technology Thick-Film MIC Technology Cofired Ceramic and Glass Ceramic Technology Design of Internally Matched Power Amplifiers Low-Noise Amplifiers Narrowband Low-Noise Amplifier Ultra-wideband Low-Noise Amplifier Broadband Distributed LNA Power Amplifiers Narrowband Power Amplifier Broadband Power Amplifier 416 References 416 Problems Monolithic Amplifiers Advantages of Monolithic Amplifiers Monolithic IC Technology MMIC Fabrication MMIC Substrates MMIC Active Devices MMIC Matching Elements 423

15 CONTENTS xiii MMIC Design CAD Tools Design Procedure EM Simulators Design Examples Low-Noise Amplifier High-Power Limiter/LNA Narrowband PA Broadband PA Ultra-Wideband PA High-Power Amplifier High-Efficiency PA Millimeter-Wave PA Wireless Power Amplifier Design Example CMOS Fabrication 448 References 449 Problems Thermal Design Thermal Basics Transistor Thermal Design Cooke Model Single-Gate Thermal Model Multiple-Gate Thermal Model Amplifier Thermal Design Pulsed Operation Heat Sink Design Convectional and Forced Cooling Design Example Thermal Resistance Measurement IR Image Measurement Liquid Crystal Measurement Electrical Measurement Technique 475 References 476 Problems Stability Analysis Even-Mode Oscillations Even-Mode Stability Analysis Even-Mode Oscillation Suppression Techniques Odd-Mode Oscillations Odd-Mode Stability Analysis Odd-Mode Oscillation Suppression Techniques Instability in Distributed Amplifiers Parametric Oscillations Spurious Parametric Oscillations Low-Frequency Oscillations 502

16 xiv CONTENTS References 503 Problems Biasing Networks Biasing of Transistors Transistor Bias Point Biasing Schemes Biasing Network Design Considerations Microstrip Biasing Circuit Lumped-Element Biasing Circuit High-PAE Biasing Circuit Electromigration Current Limits Self-Bias Technique Biasing Multistage Amplifiers Biasing Circuitry for Low-Frequency Stabilization Biasing Sequence 524 References 525 Problems Power Combining Device-Level Power Combining Circuit-Level Power Combining Graceful Degradation Power Combining Efficiency Power Dividers, Hybrids, and Couplers Power Dividers Hybrids Coupled-Line Directional Couplers N-Way Combiners Corporate Structures Power Handling of Isolation Resistors Spatial Power Combiners Comparison of Power Combining Schemes 553 References 553 Problems Integrated Function Amplifiers Integrated Limiter/LNA Limiter/LNA Topology Limiter Requirements Schottky Diode Design and Limiter Configuration W Limiter/LNA Design Test Data and Discussions Transmitter Chain Variable Gain Amplifier Variable Power Amplifier Amplifier Temperature Compensation Power Monitor/Detector Protection Against Load Mismatch 580

17 CONTENTS xv Cascading of Amplifiers 581 References 581 Problems Amplifier Packages Amplifier Packaging Overview Brief History Types of Packages Materials for Packages Ceramics Polymers Metals Ceramic Package Design Design of RF Feedthrough Cavity Design Bias Lines Ceramic Package Construction Ceramic Package Model Plastic Package Design Plastic Packages Plastic Package Model Package Assembly Die Attach Die Wire Bonding Assembly of Ceramic Packages Assembly of Plastic Packages Hermetic Sealing and Encapsulation Thermal Considerations CAD Tools For Packages Power Amplifier Modules 609 References 611 Problems Transistor and Amplifier Measurements Transistor Measurements I V Measurements S-Parameter Measurements Noise Parameter Measurements Source-Pull and Load-Pull Measurements Amplifier Measurements Measurements Using RF Probes Driver Amplifier and HPA Test Large-Signal Output VSWR Noise Figure Measurements Distortion Measurements AM AM and AM PM IP3/IM3 Measurement ACPR Measurement NPR Measurement EVM Measurement 630

18 xvi CONTENTS Phase Noise Measurement Recovery Time Measurement 632 References 635 Problems 636 Appendix A. Physical Constants and Other Data 637 Appendix B. Units and Symbols 639 Appendix C. Frequency Band Designations 641 Appendix D. Decibel Units (db) 643 Appendix E. Mathematical Relationships 647 Appendix F. Smith Chart 649 Appendix G. Graphical Symbols 651 Appendix H. Acronyms and Abbreviations 653 Appendix I. List Of Symbols 657 Appendix J. Multiple Access and Modulation Techniques 661 Index 663

19 Foreword It has been a pleasure to review a book manuscript called Fundamentals of RF and Microwave Transistor Amplifiers and to reflect on the career of the author, my friend and colleague of more than 25 years, Dr. Inder Bahl. Dr. Bahl is a man who is passionate about microwaves. Microwaves are his work and his play. I recall a time when those of us working with Dr. Bahl could tell when he was on vacation because as he sat at his desk working his latest microwave project, he wasn t wearing a tie! Dr. Bahl has been a prodigious contributor to the microwave art, authoring or coauthoring over 150 papers, 12 books, serving as the editor of International Journal of RF and Microwave Computer-Aided Engineering, and successfully completing literally hundreds of low noise, power, and control MMIC designs. Beyond the science, engineering, and the math, Dr. Bahl has a canny intuitive feel for how microwave circuits behave. It is almost as though Dr. Bahl can surf the microwaves through the circuit, feeling the gains and losses, experiencing the discontinuities, and uncovering the hidden gremlins! The writing of this text is a gift from Dr. Bahl to the microwave community. Authoring a text of the scope and magnitude of Fundamentals of RF and Microwave Transistor Amplifiers is a monumental task the success of which is a tribute to Dr. Bahl s broad and extensive experience in the field, and to his dedication. His goal is to support and encourage others to participate in the microwave art to which Dr. Bahl has dedicated his life, and to share his excitement! In this book, Dr. Bahl has outlined for his readers the keys to successful transistor amplifier design. In the following text, you will get the opportunity to see the world of solid-state RF and microwave amplifiers through the eyes of a master. What does he think about? What s important? How does he proceed with a design? Sit back, read, enjoy, and get prepared for what the future will bring. The excitement is just beginning! Dr. Edward L. Griffin Roanoke, Virginia December 2008

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21 Preface Amplifiers have played a vital role in the development of high-performance and low-cost solutions for front-end RF and microwave systems. Numerous articles scattered in a wide array of technical journals and conference proceedings, book chapters, and even books have been published on amplifiers. However, no comprehensive text dedicated to this topic covering both theory and practical aspects exists. Thus there is an urgent need to bring out a book on this subject to fill the void. This book evolved basically with my transistor amplifier design experience over the past 28 years. I have been actively involved with numerous amplifier designs from the concept level to the end products. The present book provides a comprehensive treatment of RF and microwave low-noise and power amplifier circuits including, low noise, narrowband, broadband, linear, high power, high efficiency, and high voltage. The topics discussed include modeling, analysis, design, packaging, and thermal and fabrication considerations. The elements of the book are self-contained and cover practical aspects in detail. The book also includes extensive design information in the form of equations, tables, graphs, and examples and has a unique integration of theory and practical aspects of amplifier circuits. Amplifier related design problems range from matching networks to biasing and stability. Practical examples (over 80 fully solved) make it simple to understand the concepts of amplifier design. Simple design equations are also included to help the reader understand design concepts. In addition to the solved examples, over 160 problems are provided to help readers test their basic amplifier and circuit design skills. With its emphasis on theory, design, and practical aspects geared toward day-to-day applications, this book is intended for students, teachers, scientists, and practicing engineers. Students are required to have prior knowledge of topics such as solid state device basics, theory of transmission lines, basic circuit theory, and electromagnetics taught at the undergraduate level. It is hoped that through this book, readers will benefit in their quest to understand RF and microwave transistor amplifier circuit design. The unique features of this book include in-depth study of transistor amplifiers, extensive design equations and figures, treatment of the practical aspects of amplifier circuits, and description of fabrication technologies. It provides a broad view of solid state transistor amplifiers. It has dedicated chapters on topics such as stability analysis, high-efficiency amplifiers, broadband amplifiers, monolithic amplifiers, high-voltage design, biasing of amplifiers, thermal design, power combining, integrated function amplifiers, and amplifier measurements. This book is not intended to cover any specific application, however; its purpose is to present essential background material in the fundamentals of amplifier design including both theoretical and practical aspects. RF and microwave circuits using Si bipolar and CMOS technologies have made tremendous progress and an enormous number of papers have been published in recent years.

22 xx PREFACE This topic is covered in a limited scope because there are several excellent books available on this subject and amplifier designs are largely based on analog design concepts. The book is divided into 22 chapters, with the material treated precisely and thoroughly and covering various aspects of amplifiers in each chapter. These chapters present the basic principles, analysis, techniques, and designs used in transistor amplifiers and provide the foundation for the analysis and design of RF and microwave transistor amplifiers. Design procedures and examples are provided in each chapter. The step-by-step procedures help to eliminate any doubts and help the student sharpen his/her design skills. In addition, technical information and remarks on various components, devices, and circuits update the reader on the most widely used microwave techniques. It is hoped that the selection of topics and their presentation will meet the expectations of the readers. Like any other comprehensive book, the work of other researchers is included or cited for further reading. This book also includes a comprehensive list of references. Finally, most chapters have a set of problems. Chapter 1 provides an introduction to transistor amplifiers and their applications in both commercial and military systems. Chapter 2 establishes the basic amplifier analysis parameters and representation of RF and microwave networks. Fundamental network analysis tools such as impedance, admittance, ABCD, and scattering matrix techniques are introduced together with the properties of multiport networks. Relationships between the commonly used matrix representation forms are established to permit the researcher or designer to work in the system of his/her preference. Chapter 3 deals with the definition of amplifier terms and characterization of amplifiers. Fundamental amplifier parameters are defined, together with a brief introduction to reliability. The intent of this chapter is to define amplifier characteristics at one place for quick reference. Chapter 4 deals with transistors, including Si bipolar, GaAs FETs, GaAs phemts, GaAs HBTs, Si MOSFETs, and SiGe HBTs. The treatment is limited to emphasize characteristics that will be of interest to students and design engineers. Chapter 5 deals with linear and nonlinear transistor models. These models are the backbone of amplifier designs and are based on equivalent circuit formulations. The device models included are for low-noise and low-power applications. The devices included are MESFETs, phemts, HBTs, and MOSFETs. The EC model, model scaling, and source-pull and load-pull characterizations are also detailed in this chapter. In Chapter 6, the fundamentals of transmission lines and lumped elements are considered, including their characteristics. Since the book is primarily devoted to planar circuits, the characteristics of commonly used planar transmission media such as microstrip line and coplanar waveguide are described. Discontinuities and coupling aspects in the microstrip line are also covered. The design of lumped elements such as capacitors, inductors, and resistors is treated at the end of the chapter. All of this leads naturally into Chapter 7 on impedance matching networks that are fundamental to any microwave circuit or system. Impedance matching circuits for narrowband and wideband applications and their design techniques are discussed. Finally, their practical realization aspects are considered. Analyses of most commonly used amplifier classes are discussed in Chapter 8. It also provides a comparison of the various amplifier classes used for high-efficiency applications. High-efficiency operation of the power amplifiers can be obtained by operating the transistor in class B or C as well as using load impedances for class E or F. The switched-mode class-e tuned power amplifiers are widely used at low RF

23 PREFACE xxi frequencies while class-f amplifiers are realized up to microwave frequencies. Practical aspects of high-efficiency amplifiers are provided in greater detail in later chapters. The next five chapters describe amplifier designs, beginning with Chapter 9 on amplifier design methods. The fundamental design methods for amplifiers, including linear, nonlinear, and statistical, are described. Nonlinear circuit analysis, employing time and frequency domain simulations, is a powerful CAD tool for design and optimization of power amplifiers developed for different applications. The advantages of such tools include accurate design predicting nonlinear behavior, first-pass success for MMICs, and reduced product development time and cost. Design procedures and typical design examples are presented for GaAs FETs, phemts, and HBTs, and for Si CMOS and SiGe HBT amplifiers. Using the material in Chapter 8 as background, high-efficiency amplifier design techniques are discussed in Chapter 10. This critical component is treated in depth, starting with an overdriven class-a amplifier and concluding with harmonic tuning techniques for high PAE. Design examples are provided and important design considerations for high PAE are discussed. The design of broadband amplifiers is described in Chapter 11. Bandwidth for amplifiers is always an important consideration, and several methods used in broadbanding amplifiers are presented. This includes reactive/resistive, feedback, balanced, and distributed amplifiers. Critical design considerations for the broadband amplifiers are discussed. These circuits are seeing widespread use, particularly in electronic warfare, countermeasures, and support systems. The design of linear amplifiers is presented in Chapter 12. As in previous chapters, the emphasis is on the design of these components and thus different circuit possibilities for each component, design considerations, limitations of design, and so on are presented. Linearization techniques are discussed together with design techniques, realization aspects, and special design considerations. Chapter 13 covers the fast evolution of high-voltage transistors, which are gaining widespread acceptance and application. Pros and cons of high-voltage transistor based amplifies are described. Si bipolar and LDMOS, GaAs MESFET, phemt, and HBT and SiC MESFET and GaN HEMT devices are considered, and their design techniques are presented. Both the hybrid and monolithic high-voltage amplifiers are described. High-voltage operation employing several low-voltage transistors in series is also discussed. Using the material presented in the previous chapters, it is naturally hoped that the reader will embark on the design and fabrication of microwave integrated circuit (MIC) amplifiers. While mastering the complexity of the manufacture of these circuits can only come from years of practical experience, Chapters 14 and 15 expose one to the types of hybrid and monolithic MIC amplifiers, along with their design considerations, fabrication procedures, and design criteria. Adequate material is presented to allow the designer to make a good choice of substrates and materials for design and fabrication, for both hybrid MICs and monolithic MICs. Examples of hybrid MIC amplifiers are illustrated. Chapter 15 deals with monolithic microwave integrated circuit (MMIC) amplifiers. Several types of amplifiers are discussed and MMIC examples are presented. The next four chapters are devoted to the practical design aspect of various types of amplifiers. These include thermal design, stability analyses, biasing networks, and power combining. Chapter 16 deals with the thermal design of power amplifiers. Thermal models for channel temperature calculation for both transistors and amplifiers are described. Practical methods for thermal resistance determination are also discussed. Amplifier stability is the topic of Chapter 17. A comprehensive treatment is given of theoretical and practical aspects of amplifier stability with several examples.

24 xxii PREFACE Biasing is another important aspect for successful amplifier design, which is treated in Chapter 18. The biasing of transistors is discussed first, followed by a detailed description of biasing networks. Biasing of multistage amplifiers as well as biasing for low-frequency stabilization of power amplifiers are discussed. Chapter 19 gives an overview of power combining techniques. After the basics of power combining are described, the fundamental differences between the device and circuit combining techniques are presented. Power combiners are also covered in this chapter together with the methods for design and analysis for both hybrids and couplers. Practical examples of multichip MMIC based combined HPAs are included. Applications of amplifiers in modern commercial and military systems require cost-effective solutions. A popular technique to achieve product cost goals is to integrate more functions into a single MMIC amplifier chip or into a package or module. For example, a high level of integration at the MMIC chip level reduces the number of chips and interconnects and results in low test and assembly costs, which in turn increases the reliability and reduces the subsystem cost. Chapter 20 includes examples of this type of integration such as a limiter/lna, transmitter chains with several stages, amplifiers with variable gain and output power, amplifiers with built-in power monitors, temperature compensation for gain, and output mismatch protection. Chapter 21 deals with amplifier packaging issues. Both plastic and ceramic packages are described. Design of the feed and cavity for ceramic packages is treated in detail. Brief descriptions of die attach and wire bonding techniques are also included. Measurements of transistor and amplifiers are covered in the last chapter. The characterization of transistors is described first, followed by amplifier testing including S -parameters, noise figure, source-pull and load-pull characterization, VSWR, output power versus input power, PAE, harmonics, distortion, phase noise, and recovery time. At the end, several appendix are included to facilitate the designs of readers. This book contains enough material for a one-year course at the senior or graduate level. With judicious selection of specific topics, one can use the book for one-semester, two-semester, or two-quarter courses. Problems are given at the end of most chapters. They have been tested to ensure that their level of difficulty and complexity is suitable for the student. This book is dedicated to all my colleagues who have done pioneer work in the advancement of microwave engineering. I am also indebted to Dr. Edward L. Griffin who introduced me to the wonderful field of microwave amplifiers. He reviewed the manuscript and made excellent suggestions. Many friends and colleagues, at Tyco Electronics and elsewhere, have significantly contributed to improvements in this book. I particularly want to thank George Studtmann for critically reviewing and editing the complete manuscript, making numerous suggestions to greatly enhance the text, and also providing HBT amplifier examples. I wish to thank Mark Dayton, Andy Peake, Tom Winslow, Jain Zhao, James Perdue, and Gordon Tracy for providing critical reviews of chapters and for their support. The preparation of this book has depended on my organization and a number of very supportive individuals, including David Conway, Michael Rachlin, Janice Blackwood, and Neil Alls. I owe a special note of thanks to Linda Blankenship for expertly transforming some of my handwritten text into word-processing documents. I would like to thank Tyco Electronics management for its support and encouragement. This book became a reality only because of the great support I received from George Telecki and his staff including Lucy Hitz and Lisa Morano Van Horn at John Wiley & Sons.

25 PREFACE xxiii Finally, I want to express my deep appreciation to my wife, Subhash Bahl, for her love, encouragement, enduring unselfishness, and support. Her patience allowed me to work during many evenings, holidays, and weekends to complete this gigantic task. Especially, I wish to thank my daughter, Preeti, my son-in-law, Ashutosh, my son, Puneet, and my grandsons, Karan and Rohan, for their love, support, and patience. They all truly deserve much of the credit. Roanoke, Virginia March 2009 Inder J. Bahl

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27 Chapter1 Introduction Among electronic circuits, signal amplification is one of the most important radiofrequency (RF) and microwave circuit functions. The introduction of radar during World War II provided the first significant application requiring amplification of microwave signals. In recent times, the wireless communication revolution has provided an explosion of RF and microwave amplification applications. During the last two decades, amplifier technology has made tremendous progress in terms of devices (low noise and power), circuit computer-aided design (CAD) tools, fabrication, packaging, and applications. Low-cost power amplifiers for wireless applications are a testament to this explosion. Early microwave amplifiers were the exclusive province of vacuum tube devices such as Klystrons [1 3], traveling-wave tube (TWT) amplifiers [2 4], and magnetrons [2, 3]. Today, microwave amplification is dominated by solid state amplifiers except for applications at high output powers ( 100 watts). Today, the most common vacuum tube application is the 900-watt microwave oven using a 2.45-GHz magnetron. The power levels achievable for tube amplifiers are on the order of 10 3 higher than achievable for solid state amplifiers. The microwave oven magnetron, with a manufacturing cost of about $10 ( $0.01/watt), has no solid state competition in sight. Likewise, today s $0.50/watt 900-MHz to 2-GHz cell phone solid state transistor amplifier and $0.30/watt W L/S-band base station transistor power amplifiers have no tube competition. Solid state amplifiers are of two general classes: those based on two-terminal negative resistance diode devices, and those based on three-terminal devices known as transistors. Early solid state amplifiers were dominated by two-terminal devices because diodes are typically much easier to fabricate than transistors. Quite an array of two-terminal amplifier designs have been introduced, including parametric amplification (varactor diodes) [5 8], tunneling diodes [7 9], transferred electron diodes (Gunn and LSA diodes) [8, 10, 11], and avalanche transit-time diodes (IMPATT, TRAPATT, and BARITT) [8, 12]. Such diodes are used only for special amplifier functions. 1.1 TRANSISTOR AMPLIFIER Today, solid state amplification is dominated by use of three-terminal transistors [13 36]. Using a small voltage applied at the input terminal of the device, one can control, in an efficient manner, a large current at the output terminal when the Fundamentals of RF and Microwave Transistor Amplifiers. ByInderJ.Bahl Copyright 2009 John Wiley & Sons, Inc. 1

28 2 Chapter 1 Introduction common terminal is grounded. This is the source for the name transistor, which is a unification of the words transfer resistor. Solid state transistors may be grouped into two categories: bipolar and unipolar devices. The bipolar devices are comprised of silicon (Si) bipolar junction transistors (BJTs) and silicon germanium (SiGe) and gallium arsenide (GaAs) heterojunction bipolar transistors (HBTs). The unipolar devices include Si metal oxide semiconductor field effect transistors (MOSFETs), GaAs metal semiconductor field effect transistors (MESFETs), and pseudomorphic high electron mobility transistors (phemts). The switchover to three-terminal devices was largely due to cost. Diodes are typically less expensive to manufacture than transistors but the associated circuitry to achieve gain from a two-terminal device is much more expensive than that for a three-terminal device. For example, a transistor (without any matching network) connected between 50-ohm input and output terminals can provide db gain at radiofrequencies and 6 8 db at 20 GHz. In addition, design of three-terminal amplifiers for stable operation and routine high-yield manufacturing is exceedingly simple. Signal amplification is a fundamental function in all RF and microwave systems. When the strength of a weak signal is increased by a device using a direct current (DC) power supply, the device along with its matching and biasing circuitry is known as an amplifier. Here the DC power from the power supply is converted into RF power to enhance the incoming signal strength. If a device is a transistor, the signal is applied to the input terminal (gate/base) and the amplified signal appears at the output (drain/collector) and the common terminal (source/emitter) is usually grounded. The matching networks help in exciting the device and collecting the output signal more efficiently. Figure 1.1 shows a schematic representation of a single-stage transistor amplifier. Basic constituents are a transistor, input and output matching networks, bias circuitry, and input and output RF connections. The DC bias and RF connections may be made to connectors if housed in a fixture or to lead frame if assembled in a package depending on the amplifier fabrication scheme. There are various types of amplifiers used at RF and microwave frequencies. Basic types consist of low-noise, buffer, variable gain, linear power, saturated high-power, high-efficiency, narrowband, and broadband amplifiers. The design of Bias to connector or lead frame Bias to connector or lead frame Input to connector or lead frame Output match Via source ground Wire bond Transistor Input match Substrate Carrier or heat sink Output to connector or lead frame Figure 1.1 Schematic representation of a transistor amplifier.

29 1.3 Benefits of Transistor Amplifiers 3 amplifiers requires essentially device models/s-parameters, CAD tools, matching and biasing networks, and fabrication technology. Each type mandates additional insights to meet required amplifier specifications. For example, a low-noise amplifier (LNA) needs a low-noise device and a low-loss input matching network while a power amplifier (PA) requires a power device and low-loss output matching network. RF and microwave amplifiers have the following characteristics: Band-limited RF response Less than 100% DC to RF conversion efficiency Nonlinearity that generates mixing products between multiple signals RF coupled and no DC response Power-dependent amplitude and phase difference between the output and input Temperature-dependent gain, higher gain at lower temperatures and vice versa 1.2 EARLY HISTORY OF TRANSISTOR AMPLIFIERS The use of Si based bipolar transistors and GaAs based MESFET for amplifiers have been reported since the mid-1960s and early 1970s, respectively. Most of the initial work on Si based bipolar transistor amplifiers was below C-band frequencies, whereas GaAs based MESFET amplifiers were designed above L-band frequencies (see Appendix C for frequency band designations). Low-noise HEMTs were reported in the early 1980s. Internally matched narrowband MESFET power amplifiers working from S- through X-band were available during the 1980s and Ku-band amplifiers were introduced in the early 1990s. The GaAs monolithic microwave integrated circuit (MMIC) amplifier was reported in 1976 and since then there has been tremendous progress in both LNAs and PAs. Some of the early development milestones in MMIC amplifiers are as follows: X-band low-power GaAs MESFET amplifier in 1976 X-band GaAs MESFET power amplifier in 1979 K-band GaAs MESFET LNA in 1979 Q-band GaAs MESFET power amplifier in 1986 V-band GaAs HEMT LNA in 1988 X-band GaAs HEMT power amplifier in 1989 W-band HEMT LNA/power amplifier in BENEFITS OF TRANSISTOR AMPLIFIERS Major benefits of transistor amplifiers versus tube amplifiers are smaller size, lighter weight, higher reliability, high level of integration capability, high-volume and high-yield production capability, greater design flexibility, lower supply voltages, reduced maintenance, and unlimited application diversity. Transistors have much longer operating life (on the order of millions of hours) and require much lower warming time. Solid state amplifiers also do not require adjustment in the bias or the circuit, as required in tubes, over long periods of operation.

30 4 Chapter 1 Introduction In comparison to solid state diode amplifiers, transistor amplifiers have greater flexibility in terms of designing matching networks, realizing high-stability circuits, and cascading amplifier stages in series for high gain. The outstanding progress made in monolithic amplifiers is attributed to three-terminal transistors, especially on GaAs substrates. Monolithic amplifiers are fabricated on wafers in batches, and hundreds or thousands can be manufactured at the same time. For example, over 15,000 amplifiers, each having a chip size of 1 mm 2, can be obtained on a single 6-inch diameter GaAs wafer. Thus monolithic amplifiers have a great advantage in terms of the manufacturing cost per unit. In general, monolithic amplifiers will have advantage in terms of size and weight over hybrid integrated techniques. It is worth mentioning that the weight of an individual or discrete chip resistor or a chip capacitor or an inductor is typically more than an entire monolithic amplifier chip. Many of today s high-volume applications using amplifiers are in hand-held gadgets. Both hybrid and monolithic MIC technologies are used and considered reliable. However, a well-qualified MMIC process can be more reliable because of the much lower part counts and far fewer wire bonds. 1.4 TRANSISTORS During the past two decades outstanding progress has been made in microwave and millimeter-wave transistors. The low-noise and power performance as well as the operating voltages have significantly been advanced. Among low-noise devices, the phemt is the most popular due to its low noise figure and high gain characteristics. Other devices for small-signal applications are MESFETs, MOSFETs, and SiGe HBTs. Today, a designer has several different types of power transistors available as discrete devices (in chip or packaged form) or as part of a foundry service to design power amplifier MMICs. Several solid state devices are being used to develop power amplifier (PA) circuits including BJTs, laterally diffused metal oxide semiconductor (LDMOS) transistors, MESFETs, or simply FETs, both GaAs and indium phosphide (InP) based HEMTs, GaAs based HBTs and silicon carbide (SiC) based FETs, and gallium nitride (GaN) HEMTs. Each device technology has its own merits, and an optimum technology choice for a particular application depends not only on technical issues but also on economic issues such as cost, power supply requirements, time to develop a product, time to market a product, and existing or new markets. HEMTs have the highest frequency of operation, lowest noise figure, and high power and PAE capability. Due to the semi-insulating property of GaAs substrates, the matching networks and passive components fabricated on GaAs have lower loss than on Si. The GaAs FET as a single discrete transistor has been widely used in hybrid microwave integrated circuit (MIC) amplifiers for broadband, medium-power, high-power, and high-efficiency applications. This wide utilization of GaAs FETs can be attributed to their high frequency of operation and versatility. However, increasing emphasis is being placed on new devices for better performance and higher frequency operation. HEMT and HBT devices offer potential advantages in microwave and millimeter-wave IC applications, arising from the use of heterojunctions to improve charge transport properties (as in HEMTs) or pn-junction injection characteristics (as in HBTs). HEMTs have a performance edge in ultra low-noise, high-linearity, and high-frequency applications. The MMICs produced using novel structures such as pseudomorphic and lattice matched HEMTs have significantly improved power and power added efficiency (PAE) performance and high-frequency (up to 280 GHz) operation. The phemts that utilize multiple epitaxial III V compound layers have