Comparator performing analog correlated double sample for cmos image sensor

PURPOSE: A comparator for CMOS image sensor performing analog correlated double sampling is provided to reduce current consumption and a chip size while efficiently decreasing offset voltage of a CMOS image sensor. CONSTITUTION: A CMOS image sensor includes an image capturing unit for capturing an analog signal corresponding to the image of an object, an analog-digital converter for converting the analog signal into a digital signal using a ramp signal decreasing at a specific slope according to reference clock, and a ramp signal generator for generating the ramp signal. The analog-digital converter is composed of a chopper comparator for receiving the analog signal and the ramp signal, and an input capacitor. The input capacitor receives the start voltage of the ramp signal to abandon the level of the start voltage in a reset mode and abandons voltage having the level corresponding to the ramp signal in a counter mode in order to remove offset voltage of the CMOS image sensor.