Patent ID: 7084912

Claim:
In an Active-Pixel Sensor (APS) imaging system comprising an array of pixels arranged in rows and columns, with each pixel including a photodiode coupled to a pixel output, a circuit for generating a differential signal for coupling to an analog signal path, the differential signal consisting essentially of a combination of a reference signal and a column output, the circuit comprising: a plurality of imaging pixels; a plurality of imaging column amplifiers, each imaging column amplifier having an input coupled to a respective output of an imaging pixel; an imaging multiplexer having a plurality of inputs and an output, each imaging multiplexer input being coupled to a respective output of an imaging column amplifier, wherein the column output appears at the imaging multiplexer output; a plurality of reference pixels; a plurality of reference column amplifiers, each reference column amplifier having an input coupled to a respective output of a reference pixel; and a reference signal multiplexer having a plurality of inputs and an output, each reference signal multiplexer input being coupled to a respective output of a reference column amplifier, wherein the reference signal appears at the reference signal multiplexer output and represents a selection of the outputs of the reference column amplifiers.