theV terminals are low with respect to R1-R2, and matched. In this type of filter, C3 V IN AD621 IN AD622 should be chosen much larger than C1 or C2 (C3 ≥ C1, C2), in order to suppress spurious differential sig- nals due to CM⇒DM conversion resulting from mismatch of the R1-C1 and R2-C2 time constants.
