PURPOSE: To obtain a driving circuit in which power consumption is suppressed and fluctuation of resonance frequency due to temperature fluctuation of a piezoelectric oscillator is followed up automatically by feeding the piezoelectric voltage of the piezoelectric element, as a positive feedback voltage, to a transistor.

CONSTITUTION: Output voltage of a transistor Q1 is fed to the electrode a1 of a piezoelectric oscillator 1. Piezoelectric voltage appearing at an electrode a2 upon oscillation of the piezoelectric oscillator 1 is fed back positively to the base of the transistor Q1 thus constituting a self oscillator comprising the transistor Q1 functioning as an amplifying element and the piezoelectric element 1 functioning as a resonance circuit. The self oscillator oscillates at the resonance frequency of the piezoelectric oscillator at all times. A counter electromotive force is induced in a coil L1 and the piezoelectric oscillator 1 is driven with a voltage higher than a power supply voltage Vcc. According to the constitution, power consumption is suppressed and fluctuation of resonance frequency due to fluctuation of temperature of the piezoelectric element can automatically be followed up.