PURPOSE: To obtain a voltage detecting signal with high accuracy and very small dependancy of a threshold voltage of an MOS transistor (TR) from an output of a comparator by forming a signal being an input to the comparator with a circuit not using MOSTRs.

CONSTITUTION: The 1st and 2nd input signals are compared by a comparator circuit COMP and a voltage detection signal VOUT is obtained by inverting an output signal of the comparator circuit when voltages of the two input signals are coincident. Further, the comparator circuit COMP consists of PMOSTRs MP1, MP2 and NMOSTRs MN1, MN2 and the MP1, MP2 whose gates are connected together are connected to drains of the MP1 and MN1. Sources of the NMOSTRMN1, MN2 are connected respectively to a common potential VSS. Moreover, the drain of the MP2 is connected to the drain of the MN2 and to a waveform shaping circuit INV. A voltage detection signal VOUT is obtained from an output of the waveform shaping circuit INV.