From: firstname.lastname@example.org (Frank Miles)
Subject: Re: Historical question: negative feedback and the op amp
Date: 14 Nov 2002 18:57:40 GMT
Organization: University of Washington, Seattle
References: <email@example.com> <3DD24CD4.ECD230B9@webaccess.net> <firstname.lastname@example.org>
In article <email@example.com>,
Tony Williams wrote:
> The earliest analogue computing element that I can
> think of is the Miller Integrator, used initially
> as a linear sawtooth generator, but known as a
> mathematical integrator from day.1. F.E Terman
> credits the application of the Miller Effect to the
> integrator application to A.D Blumlein. That was
> via Blumlein's colleague F.C Williams, because
> Blumlein himself was killed in a wartime plane crash.
> I don't have any date-reference for Blumlein's work,
> mainly because (by 1939) the UK was into WWII and I
> believe that Blumlein was already working at a high
> security establishment (TRE, Malvern). However,
> Terman himself (apparently) described Blumlein's
> Integrator in his 1943 Radio Engineers' Handbook,
> based on a pentode with a feedback capacitance from
> anode-grid. He notes that Cin = Cf*(1+A), where A= gm*Rl.
> Note the "apparently". I don't have Terman's 1943
> book but have a 1950 Terman book, where he references
> back to his 1943 book in the footnotes.
I just checked my copy of Terman's 1943 REH. I haven't
been able to find any integrator, with or without pentode.
There is some nice stuff about the properties of feedback,
along with references to HS Black, H Nyquist, and other
familiar persons (no Bode, though).
Couldn't find any reference to sawtooth, ramp, or sweep
generators either. No Cin formula either -- there's
an equivalent circuit for a triode (without any
acknowledgement for what we know today as the Miller effect).
No similar equivalent is shown for the pentode.
There is a lot of amazing stuff on effects of grid design,
electron optics in CRTs, and hosts of other stuff nobody
but specialists deal with any more.