PURPOSE: To correct the dispersion in resistive elements by themselves, by detecting an error voltage at a ramp voltage generating circuit and a comparator and switching a correcting resistance array with a switch.

CONSTITUTION: Both ends of the series resistance array 16 are connected to a reference voltage input terminal 11 via correcting resistance arrays 14, 15 comprising correcting resistors and switches, and an optional voltage is outputted through any of the switches S1∼Sn. To correct the linearity of the resistance array 16, a voltage and a reference voltage at points A, B of the resistance array 16 are applied to a comparator 22 via a switch group 21 and they are compared with an output of the ramp voltage generating circuit 23. Further, a reference clock is counted by a counter 25 with the compared value and the correcting amount is obtained from the count value at each switch. The switches of the correcting resistance array 14, 15 are switched based on the correcting amount.