Patent ID: 7336214

Claim:
An image sensor circuit comprising: an array of pixels comprised of rows and columns of pixel circuits; a row driver for supplying respective control signals to rows of said pixel circuits; and respective analog to digital converters connected to receive signals produced by columns of said pixel circuits; wherein each of said analog to digital converters comprises: a first input node for receiving a reference value; a second input node for receiving a pixel signal value; an autozeroing amplifier section having respective inputs coupled to the first and second input nodes and being capable of performing an offset reduction operation to compensate for offset between its inputs; a comparator section having respective inputs coupled to respective outputs of the autozeroing amplifier section, said comparator section capable of performing an offset reduction operation to compensate for offset between its inputs and capable of performing a decision operation using positive feedback to decide which of its inputs is being provided with a higher input voltage; a group of binary scaled capacitors having respective first nodes coupled to the second input node; and a set of conversion latches connected to respective second nodes of the binary scaled capacitors, the set of conversion latches coupled to receive an output of the comparator section and comprising a logic circuit for selectively applying voltages to respective second nodes of the binary scaled capacitors in response to output values received from the comparator section, wherein signals within an analog to digital converter are amplified by the autozeroing amplifier section before being supplied to the comparator section to reduce the effect of comparator section offset on comparator section decisions.