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Use of the Non-Inverting Op Amp Input

One aspect of things that did not change as yet was the use of the op amp signal input. All of the examples in the Korn and Korn book (Reference 50, again) use the op amp with the single-input, parallel feedback mode. In fact, although some of the op amp circuit examples shown in the book have balanced, dual triode inputs, engineering practice out in the world was still in the inverting-only mode. A glance at a topology such as Fig. 4 reveals the difficulty with applying CM inputs— the amplifier simply was not designed to handle such signals. This was to change, but not very rapidly.
There are of course sound technical reasons why op amps didn't get much use in a noninverting mode. Probably the biggest single reason would be the fact that it was much more difficult to make an op amp work over a high CM range (such as ±100V) which was then used with many circuits. This would require a major redesign of the front end, and most likely would have also eliminated the use of chopper stabilization.
Despite that, one early reference to the use of the op amp in a non-inverting signal manner was by Omar Patterson, in a patent filed in 1951 (Reference 51: Omar L. Patterson, "Computing Circuits," US Patent 2,855,145, filed July 30, 1951, issued Oct. 7, 1958. (A catalog of analog computation circuits based on a fully differential input op amp circuit, including use of a voltage follower configuration)). Although Patterson's patent is a broad array of analog computing circuits, they do utilize a common op amp structure, which is detailed as his Fig. 1.
In this design Patterson uses a fully-balanced dual triode front end, with the long-tailed pair's cathode current being established by a triode tube. With the balanced plate loading and regulated cathode current, the topology would have good CM response, and be capable of handling a fairly wide range of CM voltages. This op amp is reported to have a gain as high as 10,000 (80dB), so it was capable of reasonable accuracy.
Patterson goes on in the patent to outline a voltage follower gain stage using this op amp (his Fig. 10). In the extreme case of 100% feedback, the feedback stage's gain would be unity, with high input impedance. This is quoted for use of the circuit as an improved cathode follower. Quoting directly, "The advantages of this circuit lie in its extremely low output impedance, and its high degree of independence of tube characteristics."
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