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Capacitance voltage conversion circuit, input apparatus using the same, electronic instrument, and capacitance voltage conversion method

  • US 9,261,545 B2
  • Filed: 02/07/2012
  • Issued: 02/16/2016
  • Est. Priority Date: 02/08/2011
  • Status: Active Grant
First Claim
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1. A capacitance voltage conversion circuit which converts a capacitance of each of a plurality of sensor capacitors into a voltage, the capacitance voltage conversion circuit comprising:

  • a plurality of capacitance current conversion circuits disposed in respective correspondence with the sensor capacitors, each of the capacitance current conversion circuit configured to generate a detection current corresponding to a capacitance of a corresponding sensor capacitor;

    a current average circuit configured to average the detection currents, which are generated by the capacitance current conversion circuits, to generate an average current; and

    a plurality of current voltage conversion circuits disposed in respective correspondence with the sensor capacitors, each of the current voltage conversion circuit configured to convert a difference current between a corresponding detection current and the average current into a voltage,wherein each current average circuit comprises;

    a plurality of third transistors disposed on a path of the corresponding detection current, in respective correspondence to the sensor capacitors, respective control terminals of the third transistors being connected to each other in common; and

    a plurality of fourth transistors disposed in respective correspondence with the sensor capacitors, each fourth transistor connected to a corresponding third transistor to form a current mirror circuit therewith,wherein the current average circuit outputs a current, flowing in each of the fourth transistors, as the average current.

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