An CMOS active pixel sensor (APS) imaging system include circuitry to
compensate for different analog offset levels from the CMOS pixel array.
More specifically, the compensation is performed in the analog (charge)
domain. A digital correction value, which may be measured as part of the
operation or testing of the CMOS APS system, is provided to a offset
correction block circuit, to generate an analog electrical signal. The
analog electrical signal is supplied to a sample-and-hold circuit
including a charge amplifier. The signal read from the pixel array, after
conditioning through an analog signal chain, is also supplied to the
charge amplifier, which has a linear transfer function and outputs the
compensated signal.