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Apparatus for high sensitivity, low lag, high voltage swing in a pixel cell with an electronic shutter

  • US 6,720,592 B1
  • Filed: 06/29/2001
  • Issued: 04/13/2004
  • Est. Priority Date: 06/29/2001
  • Status: Expired due to Term
First Claim
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1. A circuit for a pixel cell, comprising:

  • (a) a photogate disposed over a P−

    substrate, wherein electrons collect in a region underneath the photogate when a potential on the photogate is high and light is incident on the photogate;

    (b) an N+ floating diffusion area disposed adjacent to the photogate on the surface of the P−

    substrate and a first and a second capacitance coupled to opposite sides of a shutter transistor, the N+ floating diffusion area and the first and second capacitances storing electrons that migrate from underneath the photogate when the potential on the photogate is low;

    (c) a reset transistor coupled between the N+ floating diffusion area and a supply voltage, wherein the electrons stored in the N+ floating diffusion area move to the supply voltage when the reset transistor conducts; and

    (d) a first transistor having a gate coupled to the shutter transistor and the N+ floating diffusion area, wherein when the shutter transistor is non-conducting, a signal voltage representing light incident on the photogate is stored on the second capacitance that is coupled to one side of the shutter transistor and also coupled to the gate of the first transistor, so that the signal voltage is presented at the gate of the first transistor for read out.

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