To stably output a triangular wave whose positive and negative waveforms are symmetrical by switching a reference voltage by an output voltage whose polarity is inverted when the output voltage of an inversion integrator which integrates a positive or negative polarity output voltage from a polarity switching circuit by a time constant is made coincident with a comparison reference voltage from an invertor.

A polarity switching circuit 12 switches a band gap reference voltage VR from a reference voltage generator 11 to a positive polarity voltage +VR or a negative polarity voltage -VR whose absolute value is equal, and outputs it. An inversion integrator 13 integrates the voltage ±VR from the polarity switching circuit 12 by a time constant decided by a resistance R13 and a capacitor C13, and a comparator 15 compares a output voltage XA of the inversion integrator 13 with the output voltage of an invertor 14, that is, a comparison reference voltage obtained by polarity- inverting the output voltage ±VR of the polarity switching circuit 12, and when they are made coincident, the polarity of the output voltage is inverted. A signal level converter 16 operates the zero level conversion of the output voltage of the comparator 15, and switches the changeover switch SW of the polarity switching circuit 12.