Patent ID: 8405747

Claim:
An image sensor, comprising: an image pixel array to generate analog image signals in response to incident light; a dark pixel array to generate analog black reference signals for analog black level calibration of the analog image signals; a data bit line coupled to a line of image pixels within the image pixel array for transferring out the analog image signals from the line of image pixels; a reference bit line coupled to a line of black reference pixels within the dark pixel array for transferring out the analog black reference signals from the line of black reference pixels; a driver coupled to the reference bit line to receive the analog black reference signals; a comparator coupled to receive the analog image signals from the data bit line and coupled to receive the analog black reference signals output from the driver, the comparator coupled to offset the analog image signals with the analog black reference signals in an analog domain, wherein the comparator comprises an analog differential amplifier having a non-inverting input coupled to receive the analog image signals and an inverting input coupled to receive the analog black reference signals; an analog-to-digital converter (“ADC”) circuit coupled to an output of the comparator; and a ramp signal generator coupled to provide a ramp signal to the inverting input of the analog differential amplifier.