PURPOSE: To enable to set the operating point voltage at a correct value after resupply of power even in a constant setting section using a volatile memory by a method wherein correction inhibition of the operating point in a corrector is interrupted for a certain time after resupply of power.

CONSTITUTION: When power is off due to power failure, etc., the correction value in a reversible counter 28 is varnished. When power is resupplied after that, the counter 28 comes into the reset state and a window comparator 12 outputs a detection signal of low level, thus coming into the state where correction is inhibited. At this time, since the operating point voltage is shifted from the reference value, a level verifier 20 or 21 outputs a command signal for correction operation, but AND circuits 24, 25 are now closed for inhibition of correction. At the time of resupply of power, therefor, a switch 14 is closed for a certain time to interrupt inhibition of correction during that time. By so doing, the circuit 24 or 25 is opened so that a clock signal is input to the counter 28 to perform correction, as a result of which the operating point voltage can be set at a proper value.