Three transistor active pixel sensor architecture with correlated double sampling
First Claim
1. An active pixel sensor having a plurality of pixels with at least one pixel comprising:
- a photodetector operatively connected to a first electrical node;
a pixel signal coupling capacitor having a first side connected to the first electrical node and a second side connected to a second electrical node;
a reset transistor having a first source that is connected to the first electrical node and a second source that is connected to the second electrical node;
a reset gate on the reset transistor connected to a reset control buss and a drain on the reset transistor connected to a voltage supply buss; and
an amplifier operatively connected to the second electrical node.
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Accused Products
Abstract
An active pixel sensor having a plurality of pixels with at least one pixel comprising: a photodetector operatively connected to a first electrical node; a pixel signal coupling capacitor having a first side connected to the first electrical node and a second side connected to a second electrical node; a reset transistor having a first source that is connected on the first electrical node and a second source that it connected to the second electrical node; a reset gate on the reset transistor connected to a reset control buss and a drain on the reset transistor connected to a voltage supply buss; an amplifier operatively connected to the second electrical node; and a select transistor operatively coupled to the amplifier. The preferred embodiment of the invention has a gate electrode layer formed over at least a portion of the photodetector and functions also as the gate of the transistor amplifier. It is envisioned by the preferred embodiment that the gate electrode layer be either polysilicon or indium tin oxide (ITO) which are materials typically used as gate electrode materials.
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Citations
22 Claims
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1. An active pixel sensor having a plurality of pixels with at least one pixel comprising:
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a photodetector operatively connected to a first electrical node;
a pixel signal coupling capacitor having a first side connected to the first electrical node and a second side connected to a second electrical node;
a reset transistor having a first source that is connected to the first electrical node and a second source that is connected to the second electrical node;
a reset gate on the reset transistor connected to a reset control buss and a drain on the reset transistor connected to a voltage supply buss; and
an amplifier operatively connected to the second electrical node. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An active pixel sensor having a plurality of pixels with at least one pixel comprising:
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a photodetector having a reset mechanism operatively connected to a first side of a capacitor at a first electrical node;
a second side of the capacitor that is operatively coupled to the reset mechanism at a second electrical node;
means for activating the reset mechanism such that the first and the second electrical nodes are set to respective first and second potentials; and
an amplifier operatively connected to the second electrical node; and
wherein application of a predetermined signal to the reset mechanism resets the first electrical node and the photodetector to a predetermined first potential, the second electrical node to a predetermined second potential, and application of a second predetermined signal to the reset mechanism allows the second side of the capacitor on the second electrical node to float while the photodetector connected to the first electrical node is allowed to collect charge. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
a reset transistor having a first source that is connected on the first electrical node and a second source that is connected to the second electrical node; and
a reset gate on the reset transistor connected to a reset control buss and a drain on the reset transistor connected to a supply voltage buss.
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12. The invention of claim 10 wherein the amplifier is a source follower amplifier coupled to a select means which comprise a select transistor such that enabling the select transistor provides the source follower output signal corresponding to the magnitude of the second electrical node voltage onto an output signal buss.
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13. The invention of claim 12 further comprising a select transistor that is a row select transistor that provides the source follower output signal corresponding to the magnitude of the second electrical node voltage to a column output signal buss.
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14. The invention of claim 10 wherein the first side and the second side of the capacitor store any change in potential after application of the second predetermined signal to the reset gate.
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15. The invention of claim 10 wherein the signal coupling capacitor is formed by the photodetector, and a polysilicon layer overlapping at least a portion of the photodetector, and separated from the photodetector by a dielectric layer.
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16. The invention of claim 10 further comprising an indium tin oxide (ITO) electrode operatively connected to the photodetector to control the photodetector potential level.
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17. The invention of claim 10 wherein the signal coupling capacitor is formed by the photodetector, and an indium tin oxide (ITO) layer overlapping at least a portion of the photodetector, and separated from the photodetector by a dielectric layer.
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18. The invention of claim 10 wherein the reset mechanism further comprises a first transistor and a second transistor coupled respectively to the first and second electrical nodes.
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19. A method of making an active pixel sensor:
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providing a pixel having a photodetective element operatively coupled to reset means and amplification means;
AC coupling the photodetective element and the amplification means by a capacitive element that is electrically connected to the reset means on both sides of the capacitive element such that each side of the capacitive element is on a separate electrical node;
forming means for resetting both sides of the capacitive element to corresponding potentials; and
creating means for amplifying the potential stored on the capacitive element. - View Dependent Claims (20, 21, 22)
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Specification