Patent ID: 7940200

Claim:
A calibration method for an A/D converter including a first amplifier to amplify first and second voltage signals, a second amplifier to amplify the first and second voltage signals amplified by the first amplifier, and a comparator to compare the first and second voltage signals amplified by the second amplifier, comprising: short-circuiting input ports of the second amplifier; comparing the first and second voltage signals inputted to the comparator to obtain a first result; calibrating output voltage of the second amplifier in accordance with the first result of the comparison by the comparator; short-circuiting input ports of the first amplifier; opening the short-circuited input ports of the second amplifier; comparing the first and second voltage signals inputted to the comparator to obtain a second result; and calibrating output voltage of the first amplifier in accordance with the second result of the comparison by the comparator.