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US 6,888,572 B1Granted
Compact active pixel with low-noise image formation
AssigneeRockwell Science Center, Inc.
InventorLester J. Kozlowski
Life of this patent
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Abstract
A low-noise active pixel circuit is disclosed that efficiently suppresses reset (kTC) noise by using a compact preamplifier consisting of a photodetector and only three transistors of identical polarity, in conjunction with ancillary circuits located on an imager's periphery. The use of only three transistors with a tapered reset signal allows the optical area to be increased, while still providing a low-noise imager.
Claims13
An active pixel sensor circuit comprising:
- a photodetector;
- an access transistor connected to the photodetector;
- an electronically reconfigurable transistor, successively operated as a source follower driver and a feedback amplifier, connected to an output of the access transistor and to a signal output bus;
- a reset transistor connected between the access transistor and the electronically reconfigurable transistor, wherein the reset transistor is reset with a tapered reset signal;
- and
- a first column buffer connected to the electronically reconfigurable transistor and to the reset transistor, the first column buffer comprising:
- a first switch transistor connected to the reset transistor;
- and
- a second switch transistor connected to the electronically reconfigurable transistor;
- wherein during a reset operation, the first and second switch transistors connect the reset transistor with the electronically reconfigurable transistor to form a feedback path.
7 more elements
A CMOS imager array comprising a plurality of pixels, each pixel comprising:
- a photodetector;
- an access MOSFET having a source connected to the photodetector;
- an amplifier MOSFET having a gate connected to a drain of the access MOSFET, a source connected to a signal bus, and a drain connected to a column buffer;
- a reset MOSFET having a source connected to the drain of the access MOSFET, a drain connected to the column buffer, and a gate connected to a tapered reset signal generator;
- and
- a distributed feedback amplifier comprising the amplifier MOSFET, the reset MOSFET and the column buffer to taper reset the photodetector,
- wherein the column buffer comprises:
- a first switch transistor connected to drain of the reset MOSFET;
- and
- a second switch transistor connected to the drain of the amplifier MOSFET;
- wherein during a reset operation, the first and second switch transistors connect the drain of the reset MOSFET with the drain of the amplifier MOSFET to form a feedback path.
8 more elements
An active pixel sensor circuit comprising:
- a photodetector;
- an access transistor connected to the photodetector;
- an amplifier transistor, connected to an output of the access transistor and to a signal output bus;
- a reset transistor connected between the access transistor and the amplifier transistor, wherein the reset transistor is reset with a tapered reset signal;
- and
- a first column buffer connected to the amplifier transistor and to the reset transistor, the first column buffer comprising:
- a first switch transistor connected to the reset transistor;
- and
- a second switch transistor connected to the amplifier transistor;
- wherein during a reset operation, the first and second switch transistors connect the reset transistor with the amplifier transistor to form a feedback path.
7 more elements
Dependencies are inferred from the claim text.