Posted by mike demler on October 19, 2007
You may be familiar with a famous quote often attributed to the U.S. Patent Office commissioner back in the late 1800s: “Everything that can be invented has been invented”. While research seems to conclude that this quote is actually a long-lived urban myth, could we say something similar about analog design? Has every analog circuit that can be designed … been designed?
Before all you analog designers take offense, I should explain my motivation for posing this provocative question. Firstly, it is to encourage you to review a little history of analog design by reading an excellent set of articles published in this month’s IEEE Solid State Circuits Society newsletter. You should be able to access the articles online even if you are not an IEEE member: Tales of the Continuum: A Subsampled History of Analog Circuits by Thomas H. Lee and A History of the Continuously Innovative Analog Integrated Circuit by Ian Young.
Some of my earliest design influences are recalled here: Bob Widlar, Paul Brokaw, Alan Grebene, Hans Camenzind, and many more. If you are doing analog design and are not already intimately familiar with the contributions of these individuals, this should be required reading. If, like me, you studied the designs of these icons of analog early in your career, you will enjoy the retrospective. You may also be surprised to learn that early demonstrations of how the world is analog can be traced back to the ancient Greeks. Lee begins the history of analog design with the discovery of the first analog computer, the Antikythera mechanism, which is traced to the wreck of a cargo vessel in the Aegean Sea more than 2000 years ago!
Secondly, my purpose is to encourage designers to look back at circuit techniques that may have been published long ago, perhaps in a different context, for inspiration on how to solve problems today. Perhaps a more appropriate quote or title for this post is that “everything old is new again”. There are many examples of innovation in analog designs that have demonstrated that is true. As an example, some may think that delta-sigma techniques for ADCs and DACs are new, but do you know that the delta-sigma modulator had its origin more than thirty years earlier, in the field of communications? CMOS technology and the requirement for small, high-resolution converters created the opportunity to apply the technique that is now used almost universally in consumer electronics.
What new-old analog circuit techniques have you seen lately?