Patent ID: 7649559

Claim:
A method of sensing pixel columns, comprising: amplifying a first amplifier input to a first output and a second amplifier input to a second output; canceling an amplifier offset by selectively coupling the first output to the first amplifier input and selectively coupling the second output to the second amplifier input; with a buffer amplifier having a buffer amplifier input and having a buffer amplifier output, selectively coupling the first amplifier input to a first pixel signal at least a portion of the time when the canceling occurs by coupling the buffer amplifier input to the first amplifier input and the buffer amplifier output to the first pixel signal; with the buffer amplifier, selectively coupling the second amplifier input to a second pixel signal at least another portion of the time when the canceling occurs by coupling the buffer amplifier input to the second amplifier input and the buffer amplifier output to the second pixel signal; and selectively coupling the first pixel signal to the first amplifier input and the second pixel signal to the second amplifier input at least a portion of the time when the amplifying occurs.