[sdiy] Differential amps and noise cancellation in dsPIC 33FJ128GP802 uP's DAC

[Ingo Debus]

> Am 06.05.2021 um 09:55 schrieb Steve Lenham <steve at bendentech.co.uk>:
> 
> You're not mistaken - the input impedances of the single-opamp differential amplifier are not equal.

Sorry, my bad. You're absolutely right of course.
The two input impedances are only equal if the two input voltages are same (with respect to ground), in other words, if there’s no differential input signal.

Seems I took the superposition principle one step too far. Make things as simple as possible, but not simpler (paraphrasing Albert Einstein).

Ingo