(25) Resistance Computation adder-subtractor circuits

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An excerpt from Simple Rules for Choosing Resistor Values in Adder-Subtractor Circuits, volume 10, no. 1, 1976, pages 14 & 18, analog dialogue magazine, for the HP-25 programmable calculator.

THE PROBLEM
I want to take a linear combination of analog voltages with both positive & negative coefficients, using a single operational amplifier …
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A SOLUTION!
This is a mechanized procedure for computing all the required values. It works in all practical cases, for any number of inputs on either side, whether the circuit is inverting-only, non-inverting only, or an adder-subtractor, and for all reasonable values of gain or attenuation.
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That's all, folks!
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If many similar networks with differing gains are to be designed, the reader may be interested in an HP-25 program that will provide fast and accurate implementation of the above procedure for up to 3 inputs on each side. It appears on page 18.

BEST!
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