A blog reading all Jim Williams app notes
Kent Lundberg dropped me a note that he has decided to re-read all of JimWilliams’ app notes and book chapters and blog about the experience. His introduction to the blog says:
- Jim Williams passed away four weeks ago on June 12, 2011. He was a hero, role model, mentor, and friend. I deeply miss our flea-market sprees, our junk-store pilgrimages, and our oscilloscope-repair adventures. Most of all, I miss our effortless random conversations, discussing history, business, pranks, and, of course, circuits. Thankfully, he will never be gone completely: he left behind over 350 publications relating to analog circuit design, so generations of engineers can continue to learn from his wisdom. To fill some of the void left by his untimely departure, I’ve decided to (re)read his seven book chapters and his 62 Linear Technology application notes (over 1600 pages!) and to write some commentary as I do. Reading a long book is often compared to having an intimate conversation with the author. In effect, this is my final conversation with Jim.
I note Kent’s blog is up to App note 13. He asks why Jim did not use a Mil-spec version of the LM101, and my question is why did he use a National part at all? It would be interesting to read the National Semiconductor notes Jim wrote as well, except National took his name off them after he left for Linear Technology. I also was amused at Kent’s amazement at Jim’s use of a tunnel diode in this old app note. Heck Williams told me a few months ago that he was using obsolete tunnel diodes to whack a pulse into a brand new oscilloscope with a rise time that exceed the bandwidth of the scope. Jim noted that the displayed waveform had a little ringing artifact before the start of the pulse. I won’t name the brand of scope because my buddy analog guru Paul Grohe reminded me that this likely was the scope software “connecting the dots” and that the algorithm might well put in a pre-event artifact. Paul said you have to be sure to put the scope into “points mode,” where it just shows you the actual data points. If the rise time of that tunnel diode was faster than the bandwidth of the scope, you wouldn’t expect more than a point or two during the rise.
I feel it is a bit shameless to use my blog to push my articles, but I did want to mention the effect Jim Williams had on my recent Prying Eyes feature of the Tektronix 1101 scope probe power supply. This is a case of Jim Williams helping me out from beyond the grave. It was Jim that mentioned how cool the guts of this power supply is, and how clever the circuitry is, in that it sequences and if one of the +/-15 or 5-volt supply goes out, it will inhibit the other supplies. This came up since my buddy Martin DeLateur, the International Man of Mystery, had given me a great deal on a broken 1101 he had at the Silicon Valley eFlea. Martin was cool enough to let me have this Faberge Egg of electronics for 10 bucks, and he included a schematic as well.
So with both Jim Williams and Bob Pease dying, I was inundated with work, all extra relative to still having to get a magazine out every two weeks. Crack managing editor Amy Norcross held me together during the horrible time, letting me turn stuff in late. Fran Granville, the EDN editor who re-writes all my features so they are understandable, was turning my late things around after working over the weekend to accommodate my overload. So when Amy reminded me I had this Prying Eyes feature due, I was really worried that I would not be able to get something interest photographed and analyzed in a couple days, as opposed to the week it usually takes. Then I saw the broken 1101 sitting on my lab bench. I was reminded of what Jim Williams told me, how it was a beautiful piece of hardware. It took two seconds to whip the thing open, and sure enough, as if I very doubted it, Jim Williams was right. This thing is absolutely beautiful inside. Jim’s spirit must have been at my side, since the photographs started coming out great right from the start, with only two re-shoots to get the lighting right on a couple of shots. The words also flowed easier than any other Prying Eyes I have ever done. So I guess all this is just a way of saying “Thanks Jim Williams”. He helped me learn analog electronics with 40 years of articles and he gave me the inspiration for this great feature even after he was gone. I will miss him every day.