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Author Topic: National Semiconductor's Bob Pease & Jim Williams of Linear Technology- updated  (Read 5001 times)
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W3GMS
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« on: June 20, 2011, 04:21:53 PM »

First Jim Williams and then Bob Pease.  I did not realize Jim passed away until I read this piece about Bob passing.  Two great Analog guy gone....
Joe, W3GMS

http://www.edn.com/article/518568-Analog_engineering_legend_Bob_Pease_killed_in_car_crash.php

Here is the info on Jim Williams of LT:

http://www.edn.com/article/518496-Analog_guru_Jim_Williams_dies_after_stroke.php


---------------------------------------------------------------------------------
Here is a new link that has some great info concerning Jim:

http://www.cancomdigital.com/newsletters/EDN/Analog/1106/06_21_11/edn_analog.html

Joe, W3GMS
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Simplicity is the Elegance of Design---W3GMS
KA0HCP
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« Reply #1 on: June 20, 2011, 05:50:59 PM »

What a shock, and such a tragedy about Bob.  We all hoped he would keep writing forever.  Even us amateurs are richer for having read his columns.

b.
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New callsign KA0HCP, ex-KB4QAA.  Relocated to Kansas in April 2019.
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Patrick J. / KD5OEI
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« Reply #2 on: June 21, 2011, 12:07:10 AM »

this takes the wind out of my sails.
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Brrrr- it's cold in the shack! Fire up the BIG RIG


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« Reply #3 on: June 21, 2011, 10:02:45 PM »


Yeah, I read about this a day or so ago on DiyAudio.com... Sad

None too good, I always enjoyed Pease's column in Electronic Design mag.
Sort of like when Steven St. Croix of Mix mag died kinda young of cancer...
They "made" the magazine...

Beside Pease being a designer of considerable talent and contribution.

Cherish each day, and each contact on-the-air.

                          _-_-bear
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_-_- bear WB2GCR                   http://www.bearlabs.com
VE3GZB
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« Reply #4 on: June 24, 2011, 07:43:25 PM »

We get Electronic Design at work and the first thing I turn to is Bob's articles in the back.

I was fortunate enough to buy from himself directly a book for my stepdaughter. He wrote a book "How to drive into accidents - and how not to". He signed it too.

Sometimes I would e-mail Bob if I saw a peculiar problem and we'd banter it around. Had some occasional troublesome transistors and after talking via email he said I could mail them to him when I came across some of the odd ones (2n3904s).

My most recent e-mail to him was last week about why as a unity gain buffer an LMC6034 will oscillate under a capacitive load but an LM324 would not oscillate in the same circuit. He explained it to me very clearly! The older LM324 isn't as internally compensated as the modern CMOS LMC6034 is.

It's the internal compensation which is causing the oscillation.

We had quite a discussion about why some of us love to persist with vacuum tubes in a solid state age too!

Very sad indeed, both Jim Williams and Bob Pease gone way too early.

National has a video up to remember him.

http://www.national.com/en/corporate/remembering_bob_pease.html
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VE3GZB
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« Reply #5 on: June 24, 2011, 11:09:23 PM »

My last communication with Bob Pease. My part of the conversation is in italics. Bob's are in Bold.

Bob, I've got a question for you. Recently at work we encountered an oscillation problem and although it was not entirely unexpected, something else was a little unexpected.

For a buffered 1/2 Vcc bias buss in our RF circuitry, we use a unity gain buffer fed from a simple voltage divider feeding the non-inverting input to the buffer. The op amps that are used in the circuit are the LMC6034. Our circuit uses actually a total of 4 LMC6034s for various analog processing functions but only 1/4 of one LMC6034 is being used for this bias buss function.

*** Check. 

Because there are several RF decoupling caps on the bias buss, a number of 0.1uF and a couple of 1uf caps, oscillation out of the LMC6034 when coupled to a capacitive load was expected so we decouple the output of the opamp from the buss with a series resistor (220 ohms or something like that) and tie the op amp's inverting input to the feedpoint after the decoupling resistor.
*** Yeah,  but, as  you  observed:   220 ohms  ain't  enough ( no matter  how reasonable it seems).

Looks like this circuit:

http://i.cmpnet.com/audiodesignline/2008/03/audio_buffer_fig5t.jpg

Ok, so at the same time when we scope the bias buss looking for any noise, any RF, any path where an errant signal could end up where we don't want it, we see bits of RF and we don't want to have RF on the bias buss because it's caused RF feedback and instability before.

My boss was toying with the value of the decoupling resistor coming out of the op amp and he felt that dropping it down to 3.3 Ohms would keep the bias buss clear and free of bits of RFI.

*** Not  for  CMOS  op-amps.   Sorry.  Let me  also search  around. 

When I put that into production, I scope it and see that low frequency oscillation comes on the bias buss, not unexpected because the op amp has to now support a capacitive load, right?
*** Check.

We're constantly looking at circuit revisions depending on what kind of pricing we can get on other chips. My boss asked me to try the venerable LM324 in place of the LMC6034 we've been using for decades.
*** Check.

To my surprise the LM324 works without any trace of oscillation in this circuit when the decoupling resistor is 3.3 Ohms.

***  I  believe it.  The  LM741  also  can  be very good.

So my question is why would the LM324 work without low frequency oscillation down to 3.3 Ohms in this application and the LMC6034 oscillates when run down to 3.3 Ohms? Their output current ratings are not so entirely different when I compare the data sheets?
*** Explanation:

 - To get nice  response   as  an  op-amp,  all these  damn'  CMOS  op-amps  have  NICE  LOOPS
  around  their  output stages, inside  the  chip.  These  NICE LOOPS   cause  the output  to go  berserk  with CL.
*I'm  sorry as a bastard,  but those  NICE LOOPS do that.  At present  I don't know  anybody's  CMOS  op-amps  that  don't have  that  problem.   If  you can fit in  a bipolar op-amp,  do it  for  now.

 The  usual tricks  such as Noise Gain -  Don't help.  More  decoupling & multiple  feedback - Don't help.

I'll get  back  to you./  rap


I guess he won't be getting back to me. This e-mail was just one of many we would fire back and forth. Feels like I lost a brother.
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Tom WA3KLR
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« Reply #6 on: June 25, 2011, 06:22:52 PM »

I was very saddened to hear of the demise of both Jim Williams and Robert Pease, two of the most visible and talented analog geeks in the published engineering world today.  Pease died behind the wheel of his 1969 Volkswagen beetle he used to write about, while returning from Jim Williams’ funeral service.  What a tragic event.

I remember Jim being present at a Linear Technology seminar I attended many years ago.  I think Jim was retired from Linear Technology and active on an audio hobbyist technology website, gearslutz.com I think it was.

I won a copy of one of Bob Pease’s paperback books “Troubleshooting Analog Circuits” at a National Semiconductor i.c. seminar October 25, 1995.  

My copy of the book is autographed by him:

“Best wishes to you
- and may
all your Troubles
be Middle-sized;
so you can find ‘em!

RAP 285X95”

I have enjoyed reading Bob's column "Pease Porridge" published on the last page of electronic design magazine, for many years.  He was allowed to venture into topics not in the slightest bit about electronics such as hiking.  

R.I.P. RAP.

Highly experienced circuit design engineers like Bob and Jim are extremely rare and so they will be greatly missed in the electronics design world as others above have stated.

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73 de Tom WA3KLR  AMI # 77   Amplitude Modulation - a force Now and for the Future!
Steve - K4HX
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« Reply #7 on: June 26, 2011, 09:32:10 AM »

Quote
I have enjoyed reading Bob's column "Pease Porridge" published on the last page of electronic design magazine, for many years.  He was allowed to venture into topics not in the slightest bit about electronics such as hiking. 

Me too. Great reading and a great guy. Sorry to hear he's gone.
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