Analog: Comparator (publ. 2025-04-14)

I was very busy with some other things for a week or two, but I am working on my analog computer again. Right now I am adding a comparator to the board. The Grappendorf schematics I have been following do not have a schematic for a comparator, so I started with the comparator design in the Analog Thing (THAT) schematics. However, THAT uses Schmitt-Trigger inverters, which require a 5V supply, and I didn't want to mess around with that. So, I decided to just replace those with another inverting op amp, and to feed the op amp signals directly into the DC212B analog switch inputs. These analog switches have protection built-in so current is automatically limited to a max 20 mA, so I didn't both with any kind of current limiting of my own, though perhaps that would have been the proper thing to do. The switches will work with +/- 15V supply and a GND connection.

I haven't quite finished wiring up everything on the comparator, but I tested the initial op amps connected to the two analog switches, and I was able to feed in a square wave and get a pair of LEDs to alternate accordingly.

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