Patent ID: 8432471

Claim:
A CMOS image sensor comprising: a photodiode; a switch configured to transfer a signal sensed by the photodiode to a sensing node; and a comparator electrically and directly connected to the sensing node and configured to compare the sensed signal of the sensing node and a ramp signal, wherein reset offset of the comparator is maintained at a constant offset voltage level during an initialization mode, wherein the switch comprises an RX transistor configured to initialize the sensing node, a TX transistor configured to transfer the signal sensed by the photodiode to the sensing node, an SF1 transistor controlled by the sensed signal; and an SEL1 transistor configured to select the sensing node, and wherein the comparator comprises an M p transistor configured to be diode-connected during the initialization mode, an M off transistor configured to make diode-connected M p transistor in response to an initialization signal, and an offset capacitor configured to store a voltage level made by the diode-connected M p transistor.