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Photodiode operable in photoconductive mode and photovoltaic mode

  • US 9,366,570 B1
  • Filed: 03/10/2014
  • Issued: 06/14/2016
  • Est. Priority Date: 03/10/2014
  • Status: Active Grant
First Claim
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1. A device comprising:

  • a photodiode having a light-sensitive area, an anode, and a cathode, wherein the photodiode operates in a photoconductive mode when reverse biased, in which the photodiode generates an internal photocurrent directed from the cathode to the anode in response to light incident on the light-sensitive area, and operates in a photovoltaic mode when not reverse biased, in which the photodiode develops a voltage between the cathode and the anode in response to light incident on the light-sensitive area;

    a first voltage source;

    a second voltage source;

    a sampling capacitor coupled to an output node;

    a plurality of switches, including;

    a first switch coupled between the anode of the photodiode and the first voltage source;

    a second switch coupled between the cathode of the photodiode and the first voltage source;

    a third switch coupled between the anode of the photodiode and the sampling capacitor;

    a fourth switch coupled between the cathode of the photodiode and the sampling capacitor; and

    a fifth switch coupled between the second voltage source and either the anode or the cathode of the photodiode; and

    a controller configured to operate the plurality of switches and to obtain voltage measurements of the sampling capacitor, through the output node, so as to alternately;

    (i) configure the photodiode to operate in the photoconductive mode during a first exposure interval, and obtain, through the output node, a voltage measurement indicative of an amount of current drained through the photodiode during the first exposure interval; and

    (ii) configure the photodiode to operate in the photovoltaic mode during a second exposure interval, and obtain, through the output node, a voltage measurement indicative of a voltage developed across the photodiode during the second exposure interval.

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