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Pixel sensing circuit with common mode cancellation

  • US 8,115,497 B2
  • Filed: 11/11/2008
  • Issued: 02/14/2012
  • Est. Priority Date: 11/13/2007
  • Status: Active Grant
First Claim
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1. A capacitive sensing pixel for a biometric data detection system, comprising:

  • a first conductor supported by a semiconductor substrate;

    a second conductor supported by said semiconductor substrate, said first and second conductors being spaced apart from each other;

    a first reference voltage source providing a first input voltage having a first phase;

    a second reference voltage source providing a second input voltage having a second phase substantially opposite to said first phase;

    an inverting amplifier having an input and output;

    an input capacitor connected between said first reference voltage source and said input of said inverting amplifier;

    said first and second conductors forming at least a portion of a sensing capacitor connected between said second reference voltage source and said input of said inverting amplifier; and

    a feedback capacitor connected between said input and said output of said inverting amplifier.

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