Patent ID: 7233190

Claim:
A voltage subtracting circuit comprising: a conversion circuit which converts a first voltage input during a first period into a first current proportional to the first voltage and which converts a second voltage input during a second period following the first period into a second current proportional to the second voltage, said conversion circuit including, a first switch element which, during the first period, inputs the first voltage into the conversion circuit without inputting the second voltage into the conversion circuit and which, during the second period, inputs the second voltage into the conversion circuit without inputting the first voltage into the conversion circuit; a holding circuit which holds the first current during the first period as a third voltage and which outputs the first current during the second period on the basis of the third voltage; and a differential voltage generator which outputs a differential voltage between the second voltage and the first voltage during the second period on the basis of the second current output by the conversion circuit and the first current output by the holding circuit.