Bell Telephone Laboratories

Armando J Vera

Donald L Fraser, Jr

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 (C.sub.1 and C.sub.2). Any resulting loss is compensated for by an operational amplifier (13) in combination with third and fourth capacitors (C.sub.3 and C.sub.4) 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.

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Methuen, MA, United States of America

Armando J Vera