A comparator has P-channel field effect transistors that are supplied at respective gates with input voltages Vin and Vref, which are objects of comparison, and that act as a differential transistor pair; and N-channel field effect transistors that serve as current channels for respective drain currents of these two P-channel field effect transistors and that act as a current mirror circuit. The comparator outputs a drain voltage Vx of an N-channel field effect transistor as a signal showing a result of comparison between the two input voltages. An N-channel field effect transistor diode-connected to the comparator is interposed between drains of the N-channel field effect transistors.