Don't monkey around with analog circuits

Engineers engaged in the test or data-acquisition function frequently need to design some analog circuits. I prefer that you get your analog-design tips from sibling publication EDN (which I also edit), but self-interest aside, you can't go wrong having Analog Circuits: World Class Designs on your bookshelf. Editor Bob Pease, staff scientist at National Semiconductor, presents his own work (for example, a chapter titled “What's all this error-budget stuff, anyhow?”) as well as the work of seven contributors.

The book provides good background material on topics like feedback control and stability, and it presents the basics of op-amp topologies and data conversion. You'll find many op-amp, filter, and data-conversion circuits you can adapt to your own needs.

But what I find most interesting in this book are the chapters in which the authors shed light on how they solve design problems. In chapter 2, for example, Phil Perkins of LTX notes that he combines circuit analysis using the traditional loop and node equations with an analysis-by-inspection technique he learned at MIT. He continues applying the technique for building V-I cards that can force current or voltage into a test load.

In addition, Richard S. Burwen, one of the founders of Analog Devices, describes how he designs circuits without filling notebook pages with calculations and without screen after screen of computer simulations. “Probably, I am the last circuit designer in the world to acquire a computer,” he writes. In contrast, Bonnie Baker of Texas Instruments presents a chapter on solving analog problems in the digital domain.

My favorite chapter, though, is “The Zoo Circuit,” by Jim Williams of Linear Technology, in which the author recounts how a monkey frolicking on parallel bars helped him design a low-power CMOS voltage-to-frequency converter. I guess the lesson is that a good engineer accepts help wherever he or she can find it.