A reference voltage output terminal of first and second reference voltage generating circuits is connected to a first current input terminal of a current mirror circuit of an operational amplifier by a diode element. At the time of start-up, a reference voltage generated on the reference voltage output terminal is 0 V. Consequently, a current flows to the diode element and an offset voltage Voff is generated on the operational amplifier so that a malfunction point is caused to disappear. Accordingly, in the case where a normal operation point on which a reference voltage having an expected value is generated and a malfunction point on which an operation is stabilized with a reference voltage having a value less than the expected value are present, the generated reference voltage is raised at the time of start-up, passes through the malfunction point to reach an expected voltage value on the normal operation point and becomes stabilized. In this state, the diode element is cut off so that the offset voltage Voff is caused to disappear.