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November 5, 2009
[Pease Porridge]
What's All This 2401BG Stuff, Anyhow?
Back about 1965, when I was at Philbrick, we were doing some business with Amelco Semiconductor. I had designed a good hybrid op amp (the Q85AH) and Amelco was trying to build it, but they had some test problems, and some yield problems... so I flew out to help find and solve their problems. The first morning, I put in an hour looking at their test setup. Nothing showed up right away. So we went over to their cafeteria for a cup of coffee. Several engineers ...
October 29, 2009
[Pease Porridge]
Bob's Mailbox: Readers Respond To Recent Columns
Readers offer analog guru Bob Pease their own anecdotes about working on sensor arrays, noise rejection, and driving one-handed.
October 6, 2009
[Pease Porridge]
Bob's Mailbox: Readers Respond To "What's All This Little Guy Stuff, Anyhow?"
Design guru Bob Pease exchanges some correspondence with readers about his August 13 column, "What's All This Little Guy Stuff, Anyhow?"
September 30, 2009
[Pease Porridge]
What’s All This Driving One-Handed Stuff, Anyhow?
Analog design guru Bob Pease tackles the challenges of driving his 1969 Beetle with one hand, as he takes us on a couple of test drives.
October 1, 2009
[Pease Porridge]
What's All This Noise-Rejection Stuff, Anyhow?
IT’S WELL KNOWN THAT audio power amplifiers like to get a good set of grounds, or noise around the inputs may not be rejected properly, causing hum and buzz. So when a guy called me asking how to clean up his interface from his clean audio signals to his LM3886 power amplifier, whose ground system was pretty noisy and lumpy, I thought for a second and replied that the solution was easy (Fig....
September 8, 2009
[Pease Porridge]
Bob's Mailbox
Design guru Bob Pease answers reader questions about how to build a variable-frequency power supply and 2N706 circuit failures.
August 27, 2009
[Pease Porridge]
Bob's Mailbox
HI BOB, Quite some time ago, I sent you a circuit similar to this file (see the figure). You were very kind and answered all of my questions. However, one thing you said was that the noise gain of this circuit is 1. How did you arrive at that value? (If the VOS of the op amp changes by 1 mV, the voltage across the load R will be ...
August 20, 2009
[Pease Porridge]
What's All This Trust Stuff, Anyhow?
Contributing Editor Bob Pease recalls a lesson about trust he learned while hiking down from Everest Base Camp in the Himalayas.
July 23, 2009
[Pease Porridge]
What's All This "Little Guy" Stuff, Anyhow?
Bob Pease has a reputation for helping his readers out with problems, sometimes sending them samples, even when they aren't big customers. That's because he believes in helping the "little guy." Also, working these problems out often helps him learn something new.
July 23, 2009
[Pease Porridge]
Bob's Mailbox
HI BOB, I like your bridge amplifier (“What’s All This Bridge Amplifier Stuff, Anyhow?”). I can’t figure out what the VREF driven offset into the first stage does (It is just a tiny bias, so if the input goes ±12 µV, the circuit will keep on working. /rap) and I can’t figure out what the diode-configured transistor in the...
July 9, 2009
[Pease Porridge]
What's All This Knot Stuff, Anyhow? (Part 4)
When I was about 16, I went to work at Consolidated Cigar Corp. in Broad Brook, Conn. Shade-grown tobacco, under tent-cloth. I bicycled over there every morning in the summer. One of my first jobs in June 1957 was tying. All the tobacco plants had to be tied up with a string, to a wire overhead, to keep them from flopping over in bad weather. There were about 30 plants in a “bent” that was 30 feet long. We got paid about 11 cents per bent, as ...
June 25, 2009
[Pease Porridge]
Bob's Mailbox
HI BOB, I read your response to Arthur Williams in the April 23 column (“Bob’s Mailbox”). The answer as to whether or not to remove the ground plane underneath inductors is: it depends. If the inductors are cans or toroids, it does not matter as the fields are contained inside the inductor. If the inductors are air wound or chip inductors, it might be best to try...
June 11, 2009
[Pease Porridge]
What's All This Bridge Amplifier Stuff, Anyhow?
I was helping some engineers working on a strain-gauge preamp not too long ago. We had it functioning, but there seemed to be some bad linearity problems. We even set up a little calibrator and tried to get it linear, yet we kept getting odd errors, using the conventional amplifier setup per Figure 1. The guys said, “We don’t have to worry about precision or calibration because we’re calibrating it in ...
May 21, 2009
[Pease Porridge]
Bob's Mailbox
HI BOB, Regarding quad op amps (“Cdesign.com/ArtICles/ArtICleID/20895/20895.html">What’s All This ‘Free Amplifier’ Stuff, Anyhow?”), I thought I’d pass on this tidbit from my early days in the late 1970s. I was working at an industrial controls company on the east coast named Leeds & Northrup Co. (now defunct). (Yeah, I have collaborated...
May 7, 2009
[Pease Porridge]
What's All This Counting Stuff, Anyhow?
Once upon a time when I was about four years old, my father went up the road to buy a couple of piglets, and he took me along. We brought them home to our little farm in a burlap bag in the back of our pickup truck. I guess I must have thought this was quite exciting, because my mother thought I was overstimulated. She sent me in to the living room to take a nap, even though it was only 11 a.m. So, I lay quietly on the couch and tried to get to...
April 23, 2009
[Pease Porridge]
Bob's Mailbox
BOB, I’ve got 35 years as an electronics design engineer doing microprocessors, hardware, and quite a bit of analog. In the late 1970s, I was involved with two different slewrate- limited applications. One was control of the throttle and pitch of the props on patrol boats. The bridge could signal full ahead, and this condition would cause engine stalls. So, a slew-rate control was needed to bring the engine to full power and adjust the prop...
April 9, 2009
[Pease Porridge]
What's All This "Free Amplifier" Stuff, Anyhow?
One of my friends was working on a story. She observed correctly that an “ideal” op amp would have infinite gain and common-mode rejection ratio (CMRR)—and zero IB and VOS— and zero price. She conceded she would never get rich selling those op amps! But there is a zero-price op amp, and I have been using them for many years—over 40. Maybe you have too. Let’s assume I have used three-fourths of an LM324 for three tasks, and that is working...
March 26, 2009
[Pease Porridge]
Bob's Mailbox
DEAR MR. PEASE, The “Financial Floobydust” section of your latest piece is, I think, anything but floobydust (Jan. 15; ED Online 20410). I believe you have touched upon a fundamental weakness at the core of so much financial and macroeconomic modeling, black-box investing, and other quantitative aspects of high finance. As you...
March 12, 2009
[Pease Porridge]
What's All This Rock-Hopping Stuff, Anyhow?
Untitled Document I went on a hike last weekend. Some of the trail was uphill, some was downhill, and I hiked along fine (if slowly). That’s not a surprise. But when I had to hop across a tiny stream, ...
February 26, 2009
[Pease Porridge]
Bob's Mailbox
HI BOB, We know that the noise power generated in a resistor is proportional to temperature. If we have a resistor with a zero thermal coefficient so that the resistance is constant with the temperature, does the temperature of the resistor increase due to the thermal noise? (No, not even sub-infinitesimally! / rap) In other words, does the resistor noise create noise voltage or current in the resistor, which in turn heats the resistor to a ...
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Bob Pease obtained a BSEE from MIT in 1961 and is staff scientist at National Semiconductor Corp., Santa Clara, Calif.
