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(25) Resistance Computation adder-subtractor circuits
02-18-2022, 10:05 PM
Post: #1
(25) Resistance Computation adder-subtractor circuits
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 …

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.

That's all, folks!


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!
SlideRule
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02-19-2022, 05:07 AM
Post: #2
RE: (25) Resistance Computation adder-subtractor circuits
That is very cool! Over the decades I have used many Analog Devices parts in various products including Op-Amps, analog gates, level converters, audio CODECs and DSPs. It is one of my favorite electronic parts companies.

The HP-25 program on page 18 seems reasonably clever. I have always been amazed at what you can do with 49 steps. I found it so capable that I used my HP-25 for 10 years though High School, college and my first engineer job.

Thanks!
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