PURPOSE: To improve the offset voltage measurement accuracy.

CONSTITUTION: In the case of making usual voltage comparison operation, an analog switch 2 is set to the OFF state, the voltage comparator 1 compares analog voltages inputted from analog input terminals 51, 52 by using the analog switch 2 and a resistor 3 without any affect. In the case of testing, the analog switch 2 is turned off by a control signal inputted from a test terminal 54 at the test and a noninverting input terminal and an inverting input terminal of the voltage comparator circuit 1 are short-circuited through the analog switch 2 and the resistor 3. The analog input terminal 51 connects to a current source 4 in this test and the analog input terminal 52 connects to a voltage source 5. The offset voltage Voff is obtained by a current Ia outputted from the current source 4 and a resistance R of the resistor 3. In order to measure the offset voltage Voff with high accuracy, only the accuracy of the current of the current source 4 is to be noticed of.