Dear Dennis... EN-Genius Network's Dennis Feucht answers your design queries in his new Circuit Design Clinic! June, 2006

EN-Genius Network presents a new, interactive analog design service to readers! Send us your design questions (with relevant data; schematics in JPEG or GIF, please) for some free engineering advice from EN-Genius Network's circuit consultant, Dennis Feucht, on how you might solve a design problem or improve circuit performance. Submissions may be edited for clarity or brevity, and submitters and their email addresses will remain anonymous (unless otherwise indicated). Please send your questions to Dennis here.

Intuitive Analog Circuit Design
by Paul McGoldrick

I have to admit that the moment I saw that word "Intuitive" in this title my toes curled up a little. When I received the text for review I opened it on multiple occasions and put it back down each time because I couldn't get my brain around how I was going to express myself about this work.

The back of the book describes it as "appealing to the engineer's innate knowledge" and "This unique approach to the subject de-emphasizes mathematics so readers can develop an 'intuitive' way of thinking about analog circuit design." Wow! But in reality the book is more mathematical than anything I have picked up in a long while. As an example, we have MATLAB scripts in the Appendix and oddities like Cramer's rule solving matrices in pole splitting.

The first chapter is an introduction to analog engineering with some history of the IC and races into a log amp, a translinear circuit and then a fifth-order elliptic ladder filter. Bizarre! The second chapter leaps right into a "Review of Signal-Processing Basics" which in the author's mind means Laplace Transforms and Pole/Zero plots right up through second-order systems. The Chapters end with a set of problems (there are no answers, unless they are on the CD-ROM that is included). This goes on for an interminable sixteen chapters.

If I describe the text any further I am likely to get extremely frustrated -- and rather angry -- such as in the use of angular frequency in radians/second, instead of just plain old frequency in Hz, moves you as far away from day-to-day reality as you are likely to get.

It is this kind approach to analog electronic design which must put off an incredible number of would-be analog engineers. You would peruse this text only with the intent of passing an examination set by the author. The words SPICE and simulation are not even in the Index. I remember at college being given the "perfect op amp" route of explanation and finding it bizarre that there was no real-world approach as to what actually worked. This text uses the venerable 741 (designed by that delightful gentleman, Dave Fullagar) as an example of a commercial "plug and play" op amp, but any analog engineer worth his bacon would advise playing with nearly anything else as a first step.

I cannot recommend this book as anything but an academic treatise, and certainly it is not going to help an engineer design circuits -- and, most certainly, not intuitively. I would instead commend the new analog designer into the hands of Bonnie Baker in her A Baker's Dozen: Real Analog Solutions for Digital Designers (ISBN 0-7506-7819-4) and for more advanced designers Jim Williams (who as a totally-analog person keeps a notepad in his Palm Pilot case) in his The Art and Science of Analog Circuit Design (ISBN 0-7506-7062-2). The pages of EN-Genius Network also contain many useful design TechNotes including our series from Tim Green (of TI) on operational amplifiers, which is a fine balance between theory, simulation and the real-world result. And, for really advanced analog design techniques, go to http://www.innovatia.com and savor the lessons that Dennis Feucht has learned over the years at the leading edge of instrument design.