Patent ID: 7164375
Filing Date: 2007-01-16
Classification: H03M

Abstract:
1. An A/D conversion unit for converting an analog input voltage into a digital output voltage, said A/D conversion unit comprising: an A/D converter for outputting a digital voltage; an analog offset canceller receiving said analog input voltage and an analog offset canceling voltage obtained on the basis of said digital output voltage, and outputting to the input end of said A/D converter an analog voltage in accord with said analog input voltage minus said analog offset canceling voltage; and a digital offset canceller connected to the output end of said A/D converter, for outputting said digital output voltage that equals said digital voltage minus a digital offset canceling voltage obtained on the basis of said digital output voltage; wherein said analog offset canceller is supplied with an analog offset canceling voltage obtained on the basis of said digital output voltage with said analog input voltage set to a predetermined level; said digital offset canceller is supplied with a digital offset canceling voltage obtained on the basis of said digital output voltage with said analog input voltage set to said predetermined level and with said analog offset canceling voltage supplied to said analog canceller; and said A/D converter has a reference voltage and provides a positive digital voltage in accordance with the excess in said analog voltage relative to said reference voltage, but provides a negative digital voltage in accordance with the shortage in said analog voltage relative to said reference voltage.