A high S/N ratio and high full well capacity CMOS image sensor with active pixel readout feedback operation

We discuss results of the design and operations of a CMOS image sensor with high S/N ratio while keeping wide dynamic range. Readout gains and input-referred noises of the image sensor are improved by actively using a pixel source follower feedback operation. A 1/4-inch 5.6 mum times 5.6 mum pixel VGA color CMOS image sensor with a lateral overflow integration capacitor in pixel in a 0.18 mum 2P3M CMOS process achieves about 1.7 times the gain compared with the case where the feedback operation is not positively used, resulting in a high input-referred conversion gain exceeded 200 muV/e^-, a low input-referred noise below 2 e^- without column amplifier and a high full well capacity of about 1.3 times 10⁵ e^-.