Koji and Haixing,
We did a tolerance analysis to specify the conner frequency for passive lowpass filtering in the AA filter of Cymac. The
link to the wiki page for the AA filter goes as follows (one can have a look at the simple schematics):
http://blue.ligowa.caltech.edu:8000/40m/Electronics/BNC_Whitening_AA
Basically, we want to add the following passive lowpass filter (boxed) before connecting to the instrumentation amplifier:
Suppose (i) we have 10% error in the capacitor value and (ii) we want to have commonmode rejection
error to be smaller than 0.1% at low frequencies (up to the sampling frequency 64kHz), what would be
conner frequency, or equivalently the values for the capacitor and resistor, for the lowpass filter?
Given the transfer function for this lowpass filter:
and the error propagation equation for its magnitude:
we found that the conner frequency needs to be around 640kHz in order to have
with
