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From: email@example.com (Tom Bruhns)
Subject: Re: Historical question: negative feedback and the op amp
Date: 13 Nov 2002 12:09:11 -0800
NNTP-Posting-Date: 13 Nov 2002 20:09:11 GMT
"Mike" wrote in message news:...
> Harold Black came up with his negative feedback theory in 1927, yet the
> first op-amp wasn't invented until the 1950s.
> The op-amp seems like such a natural extension, once you know about negative
> feedback. Why did it take so long for the op-amp to come along?
I think in many respects, something that used to be called a "servo
amplifier" really is an op amp. You might discover that we've had op
amps for longer, but just not under that name. I suppose that the
name grew out of analog computing. I wish my uncle were still around;
he worked at RadLab during WWII on navigation and control, and was one
of the early users/developers of analog computation. I'm sure he'd
have had some good insights into all the history. But you can also
probably get some good info from the RadLab books. Just be ready to
recognize an op amp, even if it's not called an op amp.
I have some modules which are labeled "operational amplifier" but
which are specifically for 400Hz AC. The 400Hz is essentially a
carrier frequency for slow (by comparison to electronic circuits)
servo systems. They aren't old enough to qualify as antiques, but I'm
almost certain you can find amplifiers performing the same function in
WWII era control systems.
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