Image sensor
AssigneeSTMicroelectronics S.r.l.
InventorRobert Henderson
Life of this patent
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Abstract
An image sensor includes pixels which are of the four-transistor, PIN photodiode type. In each pixel, the charge on a photodiode is transferred by a transfer gate to a sensing node. Readout of reset and read voltages is via an amplifier. A gain capacitor is connected in feedback across the amplifier. Read and reset gates are controlled so that the pixel is reset to a virtual ground voltage controlled by the gain capacitor. This is independent of the pixel parasitic capacitance.
Claims6
An image sensor having an array of light sensitive pixels, each pixel comprising a photosensitive element which develops a charge in response to incident light, a transfer gate operable to transfer said charge to a sense node, a reset gate, a read gate, and a source follower forming part of an amplifier;
- each pixel further including a gain capacitor connected to form part of a feedback path across the amplifier controlled by the read and reset gates to reset the pixel to a controlled virtual ground voltage.
An image sensor according to any preceding claim, in which the photosensitive element is a PIN photodiode.
A method of operating a four-transistor PIN diode pixel image sensor, the method comprising transferring the photodiode charge onto a gain capacitor connected in feedback across the pixel output amplifier.
Dependencies are inferred from the claim text.