Introduction to the first edition (Tim Williams, 1990)

Electronic circuit design can be divided into two areas: the first consists in designing a circuit that will fulfil its specified function, sometimes, under laboratory conditions; the second consists in designing the same circuit so that every production model of it will fulfil its specified function, and no other undesired and unspecified function, always, in the field, reliably over its lifetime. When related to circuit design skills, these two areas coincide remarkably well with what engineers are taught at college – basic circuit theory, Ohm’s law, Thévenin, Kirchhoff, Norton, Maxwell and so on – and what they learn on the job – that there is no such thing as the ideal component, that printed circuits are more than just a collection of tracks, and that electrons have an unfortunate habit of never doing exactly what they’re told.

This book has been written with the intention of bringing together and tying up some of the loose ends of analog and digital circuit design, those parts that are never mentioned in the textbooks and rarely admitted elsewhere. In other words, it relates to the second of the above areas.

Its genesis came with the growing frustration experienced as a senior design engineer, attempting to recruit people for junior engineer positions in companies whose foundations rested on analog design excellence. Increasingly, it became clear that the people I and my colleagues were interviewing had only the sketchiest of training in electronic circuit design, despite offering apparently sound degree-level academic qualifications. Many of them were more than capable of hooking together a microprocessor and a few large-scale functional block peripherals, but were floored by simple questions such as the nature of the p–n junction or how to go about resistor tolerancing. It seems that this experience is by no means uncommon in other parts of the industry.

The colleges and universities can hardly be blamed for putting the emphasis in their courses on the skills needed to cope with digital electronics, which is after all becoming more and more pervasive. If they are failing industry, then surely it is industry’s job to tell them and to help put matters right. Unfortunately it is not so easy. A 1989 report from Imperial College, London, found that few students were attracted to analog design, citing inadequate teaching and textbooks as well as the subject being found “more difficult”. Also, teaching institutions are under continuous pressure to broaden their curriculum, to produce more “well-rounded” engineers, and this has to be at the expense of greater in-depth coverage of the fundamental disciplines.

Nevertheless, the real world is obstinately analog and will remain so. There is a disturbing tendency to treat analog and digital design as two entirely separate disciplines, which does not result in good training for either. Digital circuits are in reality only over-driven analog ones, and anybody who has a good understanding of analog principles is well placed to analyze the more obscure behavior of logic devices. Even apparently simple digital circuits need some grasp of their analog interactions to be designed properly, as Chapter 6 of this book shows. But also, any product which interacts with the outside world via typical transducers must contain at least some analog circuits for signal conditioning and the supply of power. Indeed, some products are still best realized as all-analog circuits. Jim Williams, a well-known American linear circuit designer (who bears no relation to the author of the first two editions of this book), put it succinctly when he said “wonderful things are going on in the forgotten land between ONE and ZERO. This is Real Electronics.”

Because analog design appears to be getting less popular, those people who do have such skills will become more sought-after in the years ahead. This book is meant to be a tool for any aspiring designer who wishes to develop these skills. It assumes at least a background in electronics design; you will not find in here more than a minimum of basic circuit theory. Neither will you find recipes for standard circuits, as there are many other excellent books which cover those areas. Instead, there is a serious treatment of those topics which are “more difficult” than building-block electronics: grounding, temperature effects, EMC, component sourcing and characteristics, the imperfections of devices, and how to design so that someone else can make the product.

I hope the book will be as useful to the experienced designer who wishes to broaden his or her background as it will to the neophyte fresh from college who faces a first job in industry with trepidation and excitement. The traditional way of gaining experience is to learn on-the-job through peer contact, and this book is meant to enhance rather than supplant that route. It is offered to those who want their circuits to stand a greater chance of working first time every time, and a lesser chance of being completely redesigned after six months. It does not claim to be conclusive or complete. Electronic design, analog or digital, remains a personal art, and all designers have their own favorite tricks and their own dislikes. Rather, it aims to stimulate and encourage the quest for excellence in circuit design.

I must here acknowledge a debt to the many colleagues over the years who have helped me towards an understanding of circuit design, and who have contributed towards this book, some without knowing it: in particular Tim Price, Bruce Piggott and Trevor Forrest. Also to Joyce, who has patiently endured the many brainstorms that the writing of it produced in her partner.

Introduction to the second edition (Tim Williams, 2004)

The first edition was written in 1990 and eventually, after a good long run, went out of print. But the demand for it has remained. There followed a period of false starts and much pestering, and finally the author was persuaded to pass through the book once more to produce this second edition. The aim remains the same but technology has progressed in the intervening fourteen years, and so a number of anachronisms have been corrected and some sections have been expanded. I am grateful to those who have made suggestions for this updating, especially John Knapp and Martin O’Hara, and I hope it continues to give the same level of help that the first edition evidently achieved.

Introduction to the third edition (Peter Wilson, 2012)

The third edition of the book has really been an exercise of revision rather than revolution, and I have tried to keep the philosophy the same as the original author intended. As with the second edition, the aim has been to update the technological aspects in the book, expand some sections and offer a slightly different personal perspective to hopefully further enhance the book. I am very grateful to Tim Williams for allowing me to make these revisions, and for his discussions about the book’s previous editions. I also acknowledge the advice, teaching and knowledge of many friends and colleagues over the past three decades which have provided much insight into the art of analog electronics, including my father, Tom Wilson, Frank Fisher while at Ferranti, Professor Alan Mantooth at the University of Arkansas, and Dr Neil Ross and Dr Reuben Wilcock, at the University of Southampton. I must also thank my wife, Caroline, who has tolerated my fascination with electronics for many years. I hope that further generations of electronic designers will find this edition useful and that the book will continue to provide the assistance and help to circuit designers that the previous editions have done over the last two decades.