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SIGNAL PROCESSING DEVICE AND PHOTODETECTION DEVICE

  • US 20120018621A1
  • Filed: 01/29/2010
  • Published: 01/26/2012
  • Est. Priority Date: 02/03/2009
  • Status: Active Grant
First Claim
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1. A signal processing device that outputs an electrical signal having a value according to an amount of charge generated in a photodiode according to an amount of incident light onto the photodiode, comprising:

  • an integration circuit including an integration capacitor element that accumulates a charge output from the photodiode, for outputting a voltage value according to an amount of the charge accumulated in the integrating capacitor element;

    a comparator circuit for comparing the voltage value output from the integration circuit and input thereto with a predetermined reference value, and when the voltage value has reached the reference value, outputting a saturation signal indicating that fact;

    a charge injection circuit for, based on the saturation signal output from the comparator circuit, injecting a constant amount of charge having a polarity opposite to that of the charge accumulated in the integrating capacitor element of the integration circuit into the integrating capacitor element;

    a counter circuit for, based on the saturation signal output from the comparator circuit, counting a number of times that the voltage value output from the integration circuit has reached the reference value;

    a holding circuit for holding and outputting the voltage value output from the integration circuit;

    an amplifier circuit for outputting a voltage value that is K times as large as the voltage value held and output by the holding circuit and input thereto (where K>

    1); and

    an A/D converter circuit in which a voltage value that is K times as large as the reference value is set as a maximum input voltage value, for outputting a digital value corresponding to the voltage value output from the amplifier circuit and input thereto.

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