From: Tony Williams
Subject: Re: Historical question: negative feedback and the op amp
Date: Sat, 16 Nov 2002 14:04:53 +0000 (GMT)
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In article ,
Frank Miles wrote:
> For derivation, see F.E.Terman, "Radio Engineering," 2nd
> ed., p.232, McGraw-Hill, NY. See also J.M.Miller,
> Dependence of the Input Impedance of a Three-electrode
> Vacuum Tube upong the Load of the Plate Circuit, Bur.Standards
> Sci. Paper 351: M. von Ardenne and W. Stoff, On the Values
> and the Effects of Stray Capacities in Resistance-coupled
> Amplifiers, Proc. I.R.E. Vol. 15, p. 895, Nov. 1927; E.L.
> Chafee, Equivalent Circuits of an Electron Tube and the
> Equivalent Input and Output Admittances, Proc. I.R.E. Vol.
> 17, p. 1633, Sep. 1929.
> (John Woodgate -- you're right on the mark regarding Miller)
Thanks for the research.
> He goes on to relate the input capacitance to problems related to
> tuned circuit implementations. And while he describes the reduction
> in input impedance due to negative (voltage) feedback, I still see
> no mention of integration in any form; no intentional negative
> voltage feedback.
Not in 1943, no. The patent application was in wartime
Britain, in 1942. I suppose they kept all such patent
applications in abeyance (in secret) until after the war.