Comment on remarks by Bitrex. Transcontinental phone lines required many amplifiers to boost the signal o ver such large distances. ?Simple? amplifiers drifted too m uch and caused so much distortion that the signal became unintelligible. It is recorded that ?every hour on the hour? someone had to a djust filament and plate supply voltages of every amplifier to keep the sys tem working. Harold Black invented the idea of negative feedback and showe d practically that stable amplifiers could be built.
Black H.S. (1934): Stabilised Feedback Amplifiers; Bell Syst. Tech. J. 13,
1-18. See also reprint in Proc. IEEE 72, 715-722, 1984.
Black H.S. (1977): Inventing the Negative Feedback Amplifier; IEEE Spectrum 14, 54-60.
Klein R. (1993): Harold Black and the Negative-Feedback Amplifier; IEEE Con trol Systems 13 No.4, 82-85.
This was not generally accepted since the ?theory? at the time was that this could/should not work. Luckily Harry Nyquist examined th e mathematical theory and showed that Black was correct and negative feedba ck did what had been demonstrated.
Nyquist H. (1932): Regeneration Theory; Bell Sys. Tech. J. 13, 126-147.
However the general diffusion of this idea was very slow though some recogn ised the potential:
Terman F.E., Buss R.R., Hewlett W.R., Cahill F.C. (1939): Some Applications of Negative Feedback with Particular Reference to Laboratory Equipment; Pr oc. IRE 27, 649-655
Bode H. W. (1940): Relation Between Attenuation and Phase in Feedback Amp1i fier Design; Bell Syst. Tech. J. 19, 412-454.
and it was not till considerably later (WWII intervening) with the book by Henrik Bode, Network Analysis and Feedback Amplifier Design, that it really caught on. It was fortuitous that these three, Black, Nyquist and Bode, we re colleagues at Bell Labs. It may be noted that probably the first report on what came to be known as negative feedback in electronic systems was the paper:
Miller J.M. (1919): Dependence of the Input Impedance of a Three-Electr ode Vacuum Tube upon the Load in the Plate Circuit; National Bureau of Stan dards Sci. Papers 15, No.351, 367-385.
(the consequence of grid-plate capacity) but in this case it was viewed as a deleterious effect since it decreased the bandwidth of the amplifier. How ever this paper is the origin of the term ?Miller integrator? ? for what we now know as the usual operational integrator. Re the remark s by Bitrex about the very much earlier steam engine ball regulator and Tim Wiliams regarding Maxwell it may be noted that the latter did analyse the regulator:
Maxwell J.C. (1868): On Governors; Proceedings Royal Society 16, 270-283.
Scott.