METHOD AND DEVICE FOR CLAMPING INPUT

摘要

PROBLEM TO BE SOLVED: To clamp an input voltage level to a desired voltage within an operating range of the device by calibrating an offset level added to a signal and collating the signal with a desired reference level at an output. SOLUTION: A correlation double sampling circuit 71 samples two signals on an input line 24, low frequency noise and offset in common to both the samples are eliminated and a difference signal is outputted. A black level correction circuit 77' calibrates the offset level so as to obtain a desired reference level at the output of the device. Then a clamp circuit, controls an output voltage of the correlation double sampling circuit 71 and a desired voltage level at an input of the correlation double sampling circuit 71 so as to servo within a device supply range and the operating range.