Discrete difference amplifier - DC analysis

RE: Discrete difference amplifier - DC analysis

Jan Cumps — Sun, 05 Jul 2026 10:13:29 GMT

first signal measurements.

I used a 100 mVpp, 1 kHz sinus. Output loaded with a 27K resistor.

signal at in1, in2 to ground
signal at in2, in1 to ground
same signal at both

the amp does what it needs to do. Amplifies differences, reject the same signal

AI says the gain is 7.96 dB.

> what is the gain in dB if I input 100 mV peak-to-peak and I get 250 mV peak-to-peak out?

RE: Discrete difference amplifier - DC analysis

DAB — Sat, 04 Jul 2026 20:52:47 GMT

Very interesting.

Well done Jan.

RE: Discrete difference amplifier - DC analysis

shabaz — Sat, 04 Jul 2026 15:41:19 GMT

Nice setup! Love that triple-output power supply, it looks like a very useful beast.

If anyone is interested in simulating things with KiCad, this is a suitable example project for that I think, and more useful now that people can see the values in reality too for comparison.

The screenshot shows how to get to the simulator in KiCad:

And then one button-click to run the simulation, and the values for each node in the circuit will be displayed directly on the schematic: