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Switched-capacitance coupling networks for differential-input amplifiers, not requiring balanced input signals

  • US 4,896,156 A
  • Filed: 10/03/1988
  • Issued: 01/23/1990
  • Est. Priority Date: 10/03/1988
  • Status: Expired due to Fees
First Claim
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1. A switched-capacitance coupling network responsive to the difference between voltages appearing respectively at first and second nodes for applying that difference between first and second input connections of a differential amplifier, said switched capacitor apparatus comprising:

  • a third node for receiving a common-mode voltage;

    fourth and fifth nodes for receiving respective voltages, one of which is positive in a given amount respective to said common-mode voltage and the other of which is negative in said given amount respective to said common-mode voltage, at any given time;

    a first capacitor having respective first and second plates;

    a second capacitor having respective first and second plates;

    means for generating in staggered phase relationship a first train of pulses, a second train of pulses and a third train of pulses, pulses of which trains occur cyclically in order of their train number and do not overlap;

    means for selectively connecting the first plates of said first and second capacitors to said third node only during each pulse of said first train;

    means for selectively connecting the second plates of said first and second capacitors to separate ones of said first and second nodes only during each pulse of said second train;

    means for selectively connecting the first plates of said first and second capacitors to separate ones of first and second input connections of said differential amplifier, only during each pulse of said third train;

    means for selectively connecting the second plates of said first and second capacitors to separate ones of said fourth and fifth nodes only during intervals between pulses in said second train including times when pulses appear in said first train and times when pulses appear in said third train; and

    means for selectively connecting the first plates of said first and second capacitors solely to each other during each pulse of said second train and disconnecting them from each other at least at times their second plates are connected to said fourth and fifth nodes, respectively.

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