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My encounter with the world of Bob Pease

I think knowledge and scientific facts must be shared and spread.

I have in my archives a small series of three e-mails I had exchanged back in 2009 with RAP – Bob Pease, regarding a problem I was trying to resolve in a circuit.

I had some very educational e-mail communications with this gigantic personality and exeptional scientist and personality. It was such an honour for me. We had spoken in private about some issues regarding analog electronics including noise. Unfortuantely he is not among us any more.

The specific problem was about a BJT's behaviour under some certain biasing conditions.

Some of my guesses regarding the problem were not all 100% accurate, but RAP was a great teacher and it was one of the times that I did not only have the privelege to learn “esoteric” analonics (my term for analog electronics) but also about my mistakes highlighted and pointed out by a master guru as RAP was. The problem is still very important and relevant and I share it with you:

From: “Robert A. Pease”

To: “John Piliounis”

Sent: Tuesday, January 13, 2009 12:40 AM

Subject: Next test….

Hello John,

There is an NPN transistor with its base grounded. There is a + 12-volt supply connected, driving through a 1k resistor to the NPN's emitter, to put ~ 6 mA into its emitter.

This NPN could be monolithic (LM3046) or metal can (2N2222) or plastic (2N3904) or ANY. If you apply a high-Z voltmeter (DVM or any) to the collector, what is the Vc, referred to ground? Why? Have fun. / rap

From: “John Piliounis”

To: “Robert A. Pease”

Sent: Tuesday, January 13, 2009 7:15 PM

Subject: Re: Next test….

Dear rap hello,

I just had some time to build the problem on a breadboard. I used a 12V battery (13.2 V without load), a VICOR ammeter and a PHILIPS voltmeter and I was measuring 5.8 mili-amperes from the +lead of the battery to the 1KOhm resistor before the Emitter of the 2N2222 and -0,40 volt between Collector and Ground. Base was also grounded.

So when you say WHY, you mean WHY the measured voltage has a minus sign, or WHY the measured voltage is of this low level?

As far as I know, this configuration is/may be a voltage one-stage amplifier. Very low current gain and large dependence of the Emitter’s bias voltage. Here we apply a very large positive input bias in the Emitter-Base stage, which means that we drive the NPN into the upper flat area of amplification and the Collector-Base stage has been left without a voltage source and a load.

This means that the voltmeter, when connected as: Red-lead to Collector, Black-lead to the Base/Ground, causes a current to flow on its internal resistance from Base/Ground to Collector which now is presented into this stage as more negative than Base. That's why I think we get a (-) sign on the voltmeter's reading. Correct or wrong Rap? Best, John

From: Robert A. Pease

To: John Piliounis ;

Sent: Friday, January 16, 2009 9:16 PM

Subject: Re: Next test….

Hello, John, see at ***

John Piliounis wrote:

Dear rap hello,

I just had some time to build the problem on a breadboard. I used a 12V battery (13.2 V without load), a VICOR ammeter and a PHILIPS voltmeter and I was measuring 5.8 mili-amperes from the +lead of the battery to the 1KOhm resistor before the Emitter of the 2N2222 and -0,40 volt between Collector and Ground. Base was also grounded. So when you say WHY you mean WHY the measured voltage has a minus sign, or WHY the measured voltage is of this low level?

***YES, BOTH.

As far as I know, this configuration is/may be a voltage one-stage amplifier.

*** There is no transistor action. Ain't no HOLES or ELECTRONS crossing the barrier from the emitter to the collector, to make the output go -.

*** It is – PHOTONS. NPN's glow in the dark when you zener the emitter. These illuminate the collector junction.

Very low current gain and large dependence of the Emitter's bias voltage.

*** No, it depends on the emitter CURRENT. You are right about the current gain:

The collector current is something like 0.03% of Ie.

Here we apply a very large positive input bias in the Emitter-Base stage, which means that we drive the NPN into the upper flat area of amplification and the Collector-Base stage has been left without a voltage source and a load.

*** Actually, in this case, even if you _DO_ provide a bias voltage, and a high resistor load (such as a 10-Meg DVM's input resistance) , the collector tries to go negative. That's what the light does, when you shine it on ANY P-N Junction.

** If you had two NPN's in one can, and put up a fine metal screen between them, to prevent any connection or cross-talk, the light would push both collectors negative. Even if you put up a MIRROR!

*** Why is the Vout only -0.3 or -0.4 volts? Because when you get the Vc negative compared to the base, the C-B junction starts to conduct. Photojunctions always do that.

This means that the voltmeter, when connected as: Red-lead to Collector, Black-lead to the Base/Ground, causes a current to flow on it's internal resistance from Base/Ground to Collector which now is presented into this stage as more negative than Base. That's why I think we get a (-) sign on the voltmeter's reading.

Correct or wrong Rap?

*** Well, not quite right. Not quite correct.

*** Well, if you look at one of these transistors glowing in the dark, you won't forget it.

*** But when you are all done with this transistor, you should (virtually) throw it away, as the Vbe and beta have been degraded by the zenering.

*** THIS is not found in any SPICE model, except maybe MINE.

*** Historical details later. / rap

Best, /RAP

From: “Robert A. Pease”

To: “John Piliounis” ;

“Robert A Pease”

Sent: Friday, January 16, 2009 9:25 PM

Subject: Zener

Historical background…. (Rap)

——————————————-

Hi John,

Some engineers at (Editor’s note : another rival company ) were working at that problem with the NPN with ~ 6 mA into its emitter, and the grounded Base. What is Vc?

THEY wasted so much time, and got SO pissed off at wasting their time, and not getting an answer that was satisfying, or believable, that THEY sent the problem to their (arch rival) (Editor’s note : another rival company ). (The actual test results are indeed repeatable and believable.)

The (Editor’s note : another rival company ) guys wasted so much time, and got SO pissed off at wasting their time, and not getting an answer that was satisfying, that THEY sent it to ME. (rap)

I looked at the typed problem for 5 seconds, and I knew the answer – and why. I didn't waste any time at all. (At least that part is true.) I published it in my April Fool Column. It puzzled a lot of people…)

&&& Note, some correspondents claim that part of the current is caused by Hot Carrier Injection into the surface. This may be partly true, but the light emission is sufficient to suit ME. Best regards. / rap

rap@galaxy.nsc.com

—or:

Mail Stop D2597A, National

Semiconductor, P.O. Box 58090,

Santa Clara, CA 95052-8090, USA.

Bob Pease obtained a BSEE from MIT in 1961 and is staff scientist at National Semiconductor Corp., Santa Clara, Calif.

2 comments on “My encounter with the world of Bob Pease

  1. carlpic44
    October 30, 2015

    I remember the seminars done by Bob Pease were very lively. Power point was not allowed and he could manipulate the foils on an overhead projector so fast that you didn't need animated graphics.

    On my last encounter with him, I accquired an autographed copy of his book “Accidents and how to avoid them” I think it was called, with a cartoon picture of his beloved Camper van on the front. Ironically it was this car that he died in when returning from a friend's funeral I believe.

    he was definitely one of the analogue Guru's that cannot be replaced.

    Carl Scargill

  2. Victor Lorenzo
    October 31, 2015

    I met him at Barcelona years ago in a seminar. His presentation included Power Point slides….with pictures of hand writen notes and diagrams.

    We talked a few minutes before lunch about ways to solve a design problem I was facing at that time during development of one portable device.

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