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

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 switch, 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 switch 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 switch closes;
• and
• (d) a first transistor having a gate coupled to the shutter switch and the N+ floating diffusion area, wherein when the shutter switch is open, a signal voltage representing light incident on the photogate is stored on the second capacitance that is coupled to one side of the shutter switch 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.

A pixel cell circuit, comprising:

• (a) means for collecting charges underneath a photogate when the photogate is active, a shutter is open and light is incident on the photogate;
• (b) means for storing electrons comprising a first means for storing electrons that is arranged to store electrons on a first side of the shutter, and a second means for storing electrons that is arranged to store electrons on a second side of the shutter, wherein the electrons migrate from beneath the photogate to the means for storing electrons when the photogate is inactive and the shutter is closed, and wherein the first side of the shutter is coupled to the photogate when the shutter is open;
• (c) means for closing the shutter to isolate a storage node on one side of the shutter;
• (d) a signal voltage that is related to the charge of the stored electrons, the signal voltage being representative of the amount of light incident on the photogate when the shutter is closed;
• and
• (e) means for reading out the signal voltage.