Pinned photodiode CMOS image sensor with a low supply voltage
AssigneeSTMicroelectronics S.r.l.
InventorsFrédéric Barbier, Yvon Cazaux
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Abstract
A device for controlling an image sensor including at least one photosensitive cell including a photodiode capable of discharging into a sense node via a first MOS transistor, the sense node being connected to the gate of a second MOS transistor having its source connected to a processing system. The device includes a bias circuit capable of increasing the voltage of the source during the discharge of the photodiode into the sense node.
Claims20
A device for controlling an image sensor comprising an array of columns of photosensitive cells, each photosensitive cell of a same column being connected to a read column, said read column being connected to a processing circuit, at least one of the photosensitive cells comprising a photodiode capable of discharging into a sense node via a first MOS transistor, the sense node being connected to the gate of a second MOS transistor, wherein the second MOS transistor has a source directly connected to the read column without interposition of an intermediate MOS transistor, said device comprising a bias circuit adapted to increase the voltage of said read column during the discharge of the photodiode into the sense node, wherein the device is configured to change a bias of the sense node during a reset period of the sense node to a voltage level lower than a voltage level of the sense node at a start of the reset period.
A method for controlling an image sensor comprising an array of columns of photosensitive cells, each photosensitive cell of a same column being connected to a read column, said read column being connected to a processing circuit, at least one of the photosensitive cells comprising a photodiode capable of discharging into a sense node via a first MOS transistor, the sense node being connected to the gate of a second MOS transistor, wherein the second MOS transistor has a source directly connected to the read column without interposition of an intermediate MOS transistor, said method comprising:
- increasing the voltage of said read column during the discharge of the photodiode into the sense node;
- and
- changing a bias of the sense node during a reset period of the sense node to a voltage level lower than a voltage level of the sense node at a start of the reset period.
An image sensor comprising:
- a photosensitive cell having a photodiode configured to discharge into a sense node via a first MOS transistor;
- a second MOS transistor having a gate coupled to the sense node and a source directly connected to a read column without interposition of an intermediate MOS transistor;
- and
- a bias circuit adapted to increase a voltage of the read column during the discharge of the photodiode into the sense node, wherein the image sensor is configured to change a bias of the sense node during a reset period of the sense node to a voltage level lower than a voltage level of the sense node at a start of the reset period.
Dependencies are inferred from the claim text.