In a conventional CMOS image sensor, an A/D converter for performing A/D
conversion at high-speed arranges the A/D converter elements in columns
so as to operate in parallel, and has low resolution in the order of 9 or
so bits. The present invention provides an A/D converter for an image
sensor, which performs a part of the A/D conversion functions by using a
noise cancellation circuit in columns and performs amplification
simultaneously with this, thereby obtaining a high signal noise ratio
(SNR) and implementing an A/D converter with a high resolution along with
the A/D conversion section in a subsequent stage.