Abstract: A ramp generator includes a supply voltage sampling circuit coupled to sample a black signal supply voltage during a black signal readout, and an image signal supply voltage of the pixel cell during an image signal readout of a pixel cell. A first integrator circuit receives a buffered reference voltage, and an output of the supply voltage sampling circuit. First and second switches are coupled between the first integrator circuit and a first capacitor to transfer a signal representative of a difference between the image signal supply voltage and the black signal supply voltage to the first capacitor. A second integrator circuit is coupled to the first capacitor to generate an output ramp signal coupled to be received by an analog to digital converter. A starting value of the output ramp signal is adjusted in response to the difference between the image signal and the black signal supply voltage.