Biasing scheme for large format CMOS active pixel sensors
First Claim
Patent Images
1. An image sensor comprising:
- a pixel array including a plurality of pixels arranged in rows and columns, each pixel comprising a photosensor and a source follower transistor for reading out photosensor charges, said array further including a plurality of column lines to which pixels in a column can be coupled; and
a plurality of read-out circuits respectively coupled to at least some of the plurality of column lines, each of the read-out circuits configured to provide pixel output signals and including a capacitor load having a first end connected to a reference voltage line and a second end switchably coupled through a first switch to a respective column line, and a second switch for directly coupling the first and second ends of said capacitor load together.
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Abstract
An image sensor includes circuitry compensating for voltage drops in a VSS line. The image sensor includes a plurality of photoreceptors arranged in a pixel array having a number of column lines, and read-out circuitry on the column lines. The read-out circuitry provides substantially equal currents on each column line so as to compensate for voltage drops in the VSS line and provide more accurate pixel signals. The image sensor also includes circuitry for filtering noise from a voltage supply line, and for providing hard and/or soft reset operations.
14 Citations
18 Claims
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1. An image sensor comprising:
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a pixel array including a plurality of pixels arranged in rows and columns, each pixel comprising a photosensor and a source follower transistor for reading out photosensor charges, said array further including a plurality of column lines to which pixels in a column can be coupled; and a plurality of read-out circuits respectively coupled to at least some of the plurality of column lines, each of the read-out circuits configured to provide pixel output signals and including a capacitor load having a first end connected to a reference voltage line and a second end switchably coupled through a first switch to a respective column line, and a second switch for directly coupling the first and second ends of said capacitor load together. - View Dependent Claims (2, 3)
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4. An imager comprising:
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a plurality of photoreceptors arranged in an array to form a plurality of columns of image sensors, each column of image sensors having associated circuitry comprising; a first capacitive load having a first end connected to a reference line and a second end switchably coupled to a column line; and said reference line being switchably coupled directly to said second end of said first capacitive load. - View Dependent Claims (5, 6, 7, 8)
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9. A method of forming an active pixel sensor, the method comprising:
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forming a pixel array having a plurality of column lines; and forming readout circuitry for the column lines, said readout circuit containing; a plurality of first storage areas, each storage area having a first and second end, switches for switchably coupling said first storage areas to at least some of the plurality of column lines, respectively, switches for switchably coupling said first storage areas to a reference voltage, and switches for directly coupling said first and second ends of said storage areas together. - View Dependent Claims (10, 11, 12)
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13. A camera system comprising:
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an array of pixels for providing signals in response to an applied image, said array comprising; a plurality of columns of pixels associated with respective column lines, each column line being associated with a readout circuit, each readout circuit comprising; a first capacitive load; a first switch for selectively coupling a first end of said first capacitive load to a column line; a reference voltage line being coupled to a second end of said first capacitive load; a second switch for selectively coupling directly the first and second ends of said first capacitive load; and a processing circuit arranged to receive said signals from said array of pixels. - View Dependent Claims (14, 15)
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16. A method of operating an image sensor comprising:
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selectively coupling directly a first side of a first capacitive load to a reference voltage line; coupling directly a second side of said first capacitive load to said reference voltage line; selectively coupling said first side of said first capacitive load to a pixel array column line, when said first side of said first capacitive load is not coupled to said reference voltage line, to receive a first signal output by a pixel coupled to said column line; selectively coupling directly a first side of a second capacitive load to said reference voltage line; coupling directly a second side of said second capacitive load to said reference voltage line; and selectively coupling said first side of said second capacitive load to said column line, when said first side of said second capacitive load is not coupled to said reference voltage line, to receive a second signal output by said pixel coupled to said column line. - View Dependent Claims (17, 18)
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Specification