Content text 5-Analog Circuit Design by Phillip E. Allen Douglas R. Holberg.pdf
Third Edition CMOS Analog Circuit Design Phillip E. Allen Professor Emeritus, Georgia Institute of Technology Douglas R. Holberg Consultant NewYork Oxford OXFORD UNIVERSITY PRESS
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xi PREFACE T he objective of the third edition of this book continues to be to teach the design of CMOS analog circuits. The teaching of design reaches far beyond giving examples of circuits and showing analysis methods. It includes knowing the necessary fundamentals and background and applying them in a hierarchical manner that the novice can understand. Probably of most importance is to teach the concepts of designing analog integrated circuits in the context of CMOS technology. These concepts enable the reader to understand the oper- ation of an analog CMOS circuit and to know how to change its performance. In today's com- puter-oriented thinking, it is crucial to maintain personal control of a design, to know what to expect, and to discern when simulation results may be misleading. As integrated circuits become more complex, it is crucial to know “how the circuit works.” Simulating a circuit without the understanding of how it works can lead to disastrous results. How does the reader acquire the knowledge of how a circuit works? The answer to this question has been the driving motivation of this text beginning with the first edition. There are several important steps in this process. The first is to learn to analyze the circuit. This analysis should produce simple results that can be understood and reapplied in different cir- cumstances. The second is to view analog integrated-circuit design from a hierarchical view- point. This means that the designer is able to visualize how subcircuits are used to form circuits, how simple circuits are used to build complex circuits, and so forth. The third step is to set forth procedures that will help the new designer come up with working designs. This has resulted in the inclusion of many “design recipes,” which became popular with the first and second editions and have been enlarged in the third edition. It is important that the designer realize that there are simply three outputs of the electrical design of CMOS analog circuits. They are (1) a schematic of the circuit, (2) dc currents, and (3) W/L ratios and component values. Most design flows or “recipes” can be organized around this viewpoint very easily. Previous Editions The first edition of CMOS Analog Circuit Design published in 1987 was the first to present a hierarchical approach to the design of CMOS analog circuits. Since its introduction, it has
xii PREFACE found extensive use in industry and classrooms worldwide. Of course, technology advances and methodologies mature, making it clear that the first edition needed revision. The second edition resulted from a unique blending of industry and academia. Between the period of the first and second editions (15 years), over 50 short courses were taught from the first edition to over 1500 engineers worldwide. In these short courses, the engineers demanded to understand the concepts and insights to designing analog CMOS circuits, and many of the responses to those demands were included in the second edition. In addition to the industrial input to the second edition, the authors have taught this material at Georgia Institute of Technology and the University of Texas at Austin. This experience provided insight that was included in the second edition from the viewpoint of students and their ques- tions. Moreover, the academic application of this material has resulted in a large body of new problems that were given as tests and included in the second edition. Third Edition The third edition has focused on cleaning up the material and removing that which is not used. Homework problems that were not effective have been removed and replaced by better prob- lems. This edition has introduced the idea of design problems. These problems give the desired specifications and a score for grading the problem. The reader is to do the design by hand and then use the computer to simulate the performance and extract the score. These are great vehicles for teaching the trade-off of optimizing the score versus the time spent. Also in this edition, answers to selected problems are found at the back of the book. Key changes to the third edition are as follows. • The technology in Chapter 2 has been updated and a new appendix created to give details on layout (Appendix B). • In Chapter 3 the large-signal MOS model has been extended to include velocity saturation. • In Chapter 4, the bandgap section has been updated and completely rewritten. • The cascode op amps in Chapter 6 have been updated and the enhanced-gain technique used to create op amps with ultra large voltage gains. • In Chapter 7, the differential-in, differential-out op amps have been updated and the material on output common-mode feedback expanded. • Chapter 9, on switched capacitor circuits, was removed and condensed into Appendix E. • A design illustration was presented in Section 10.5 to show the steps in designing an open-loop, buffered, sample-and-hold circuit. • Also included in Chapter 9 at the conclusion is the website to an Excel spreadsheet that has all published ADC converters from 1997 through 2010. This information is extremely useful for understanding the trends in converters. • Design problems have been introduced. These problems give the desired specifications and a score for grading the problem. The reader is to do the design by hand and then use the computer to simulate the performance and extract the score. These are great vehicles for teaching the trade-off of optimizing the score versus the time spent. • Readers of the previous editions have requested answers to the problems. In this edi- tion, answers to selected problems are found at the back of the book.