From: Chuck Simmons
Organization: You jest.
X-Mailer: Mozilla 4.61 [en] (X11; U; Linux 2.0.33 i586)
Subject: Re: Historical question: negative feedback and the op amp
Date: Wed, 13 Nov 2002 12:59:23 GMT
NNTP-Posting-Date: Wed, 13 Nov 2002 04:59:23 PST
Tony Williams wrote:
> In article ,
> Mike wrote:
> > Harold Black came up with his negative feedback theory in 1927, yet the
> > first op-amp wasn't invented until the 1950s.
> I think the term operational amplifier was used before
> then, in analogue computers, possibly during WWII and
> therefore not immediately publishable.
There might well have been some of that in WWII. However, a lot of
analog computing devices used then were electromechanical and used AC
carrier control. Examples would be the Norden Bomb Sight and the B-29
fire control system. I am less familiar with naval applications but it
appears that guns on ships may have used AC carrier control (especially
ships built near the end of the war). One problem with DC amplifiers is
that it is hard to make low drift vacuum tube DC coupled amplifiers and
generally it was a good idea to avoid them in critical applications.
BTW, I never actually saw a Norden Bomb Sight but there were lots of
B-36 Bomb Sights around in the late 50s and early 60s and I looked at
those pretty carefully. They were said to be similar to the Norden.
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons firstname.lastname@example.org