Switched capacitor filter

摘要

A switched capacitor filter circuit which closely matches single pole RC filters at voice frequency. The filter pole is determined by the ratio of a first and second capacitor (C1 and C2). Any resulting loss is compensated for by an operational amplifier (13) in combination with third and fourth capacitors (C3 and C4) operating as a voltage divider circuit. A switch (16) may be provided for discharging one of the latter capacitors during nonsampling intervals. A further switch (17) may also be provided to cancel charge due to gate-to-drain overlap of the first switch.