carlgrace wrote on Jul 8th, 2011, 10:16am:( C3 || (C1 + C2) ) + expected external load
That should be good enough for some ac analysis to look at gain and such. But be sure you do extensive transients to look for ringing.
Hi Carlgrace,
That assumption looks a little bit conservative to me. In my opinion C1 and C2 do not act as a capacitive load since:
1) They are connected to opamp virtual ground during phase 2 --> thus there is no AC voltage signal accross them and therefore they do not act as a load.
2) I would use the equivalent CT resistor they represent when running AC simulations
So total load for me would be C3 + external load, and an input impedance of 1/fck*(C1+C2)
Best
Tosei