[sdiy] Newbie questions about summing buffers
David G Dixon
dixon at mail.ubc.ca
Fri Feb 24 20:36:33 CET 2012
> >Capacitor across Rf forms a low pass filter, helps dampen any high
> >frequency oscillations at the output.
> People often write this but it isn't quite true. The
> feedback cap stabilizes the circuit by compensating for opamp
> nonidealities, not by acting as a LP filter. IOW you can't
> clculate the cap size just from the frequency of the spurious
> oscillations. There is a good TI writeup about this online somewhere.
I've been reading up on this stuff myself -- break points and loop gain and
all the rest of it -- but I must confess that when I've got spurious
oscillations in a circuit, I use good old trial and error to find the cap
value which eliminates them.
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