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Review of Jim Williams: Analog Circuit Design

Butterworth-Heinemann, 1991, 400 pages

In June 2011, two of the most popular analog designers, Jim Williams and Bob Pease, died within a few days. This book, edited by Jim Williams, discusses many different aspects of analog design with contributions from a lot of famous designers. It contains 4 chapters by Jim Williams and 2 chapters by Bob Pease. And you can get many of their writings for free at Application Notes by Jim Williams and Columns and Application Notes by Bob Pease. Please note that this is not a textbook on analog circuit design. Each of the contributing authors was given the freedom to write about whatever aspect of analog electronics he wanted. The subtitle "Art, Science, and Personalities" sums it up quite nicely.

In chapter 4 Williams explains why analog circuit designers will always be in demand, even though the majority of developers work in digital design - the world itself is analog after all. In chapter 13 he warns against the false promise that computer tools will make the design of electronic circuits a trivial task - 20 years later this warning is still very relevant. From a technical point of view, however, his other 2 chapters are much more interesting. In chapter 7 he discusses an oscillator that is based on the Wien Bridge. The fascinating thing is that he starts with a circuit from 1939 that used a lamp for amplitude stabilistation. Williams built this circuit with modern components (using an op amp instead of tubes) and discusses in much detail how he modified it step by step (he even discusses the steps that went into the wrong direction), until he finally arrived at an oscillator with less than 3ppm distortion. On p.52 he describes what he calls Williams Rule: "Always Invert (except when you can't)" - it refers to using an op amp in the inverting amplifier configuration, because this will make your circuit independent of the op amps CMRR. You can get a short version of this chapter for free in AN43 Bridge Circuits p.29. In chapter 23 he describes in detail how he developed a voltage to frequency converter with a maximum power consumption of 200uA. He started with a voltage to frequency design by Bob Pease and discusses how, with several step by step modifications and finally one very clever idea, he arrived at the final circuit. A short version of this chapter is in the free app note AN23 Micropower Circuits for Signal Conditioning p. 10 "10 kHz Voltage-to-Frequency Converter" and p.18 Box Section A (you should have a look at it even if you own the book - the schematics in the app note are much easier to read than his hand drawn version in the book).

In chapter 9 Bob Pease tells the story of the P2, a solid state operational amplifier from 1960 with only picoamperes of input current. It is an awfully complicated circuit, so this chapter is historically interesting, but it will not teach you how you can design your circuits. More relevant to current technology is chapter 29: Pease desrcibes how he built a voltage to frequency converter of the charge dispensing type (the 4701) in 1967 while he was at Philbrick. He desribes the principle of operation of the circuit and some interesting tricks he used in detail. This V/F converter evolved into a highly successfull product line for Philbrick. Later when Pease joined National Semiconductor he designed the LM331, a V/F converter IC.

Some chapters by other authors that I found most interesting: In chapter 16 Brokaw describes some building blocks for the linear IC designer, with a very good discussion of several variants of current mirrors. In chapter 24 Bowers first gives a short introduction to the history of the Analog IC (when you read the section "So Where Are We Today ?", please remember that "Today" was 1991...) But what he calls "Philosophical Considerations" is timeless. He then gives some advice about SPICE (you can find more of this in chapter 27 by Kennedy). Franco, author of Design with Operational Amplifiers and Analog Integrated Circuits, has contributed chapter 25 about current feedback amplifiers, Sheingold gives an introduction to Op Amps and their characteristics (chapter 30), Matthys compares several designs for Crystal Oscillator circuits (chapter 28). Other authors describe their approach to design (and even inventing new concepts) and troubleshooting in general, often with some personal history mixed in.

So who should read this book ? It will not help you to pass your exams. And if you need some specific information to help you to design a circuit, it is unlikely that you will find it in the book - it contains some very good information, but like isolated nuggets of wisdom from a very wide range of unrelated topics. What the book does very good, is to show the enthusiasm for analog electronics of many different personalities. If you feel the same enthusiasm for analog, you will enjoy reading it. Also if you are yet undecided whether analog electronics is for you, the wide range of topics that are presented may help with you with your decision. However, please note that the book is from 1991 (and some authors focus on some historical aspect of electronics ranging back to the 1960s or even earlier), so some areas of analog electronics that are hot today are not covered. Apart from the fun that you will have reading the book, you can benefit from it in the long term. You will learn about many different approaches to analog design, and you can choose the one that best suites your own style.

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