OFFSET/DRIFT CORRECTING CIRCUIT FOR ANALOG-DIGITAL CONVERTER

摘要

PURPOSE:To correct an offset of an A/D converter to a desired value at all times by integrating an analog quantity corresponding to the least significant 1 bit of the A/D converting circuit outputted from a correction pulse generating circuit at each conversion to obtain an offset setting value. CONSTITUTION:A voltage difference between an analog voltage and a correction voltage given via switches 1, 2 is amplified 3, A/D-converted 4 sequentially and a desired offset value is set 5. A digital output value of the converter 4 is compared 6 with the offset setting value at the correction mode and a signal for polarity selection is outputted. Every time the converter 4 conducts A/D conversion, a correction pulse corresponding to analog quantity corresponding to the least significant 1 bit of the converter 4 is generated 7. The polarity of the pulse is selected by a signal of a polarity changeover circuit 8, an integration citcuit 9 integrates and holds the correction pulse and outputs it as a correction voltage.