Hello,
I am looking at an application note for a current to voltage converter utilizing an opamp. There is an input capacitance across the inputs to the opamp, which the application note says introduces a zero at f =
1/(2 Pi R_feedback C) in the noise gain transfer function. This doesn't make sense to me. Shouldn't a shunted cap introduce a pole by attenuating the input signal as the cap shorts? The only way I can resolve this is by thinking that what they mean is that at higher frequencies the capacitor shunts out the signal to be amplified, and therefore noise dominates, introducing an effective zero in the noise gain transfer function. Does this make sense?The application note that I am looking at is on page 20 of:
Cheers, Chris