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

[Guy McCusker]

> Ignoring the capacitor to make life easier, a signal connected at R7
> sees 20k to ground always.
> With the input at R7 grounded, a signal connected at R6 sees 10k to
> the virtual ground. I can't see any circumstances under which a signal
> at R6 sees 20k to ground.
>
> What am I missing?

One thing I was missing is that the 6 I thought I saw was really a 5:
replace R6 by R5 in the above. Sorry.

Guy.