PURPOSE: To ensure compensation of temperatures of a wide range and to simplify the circuit constitution by providing a series circuit of the 1st and the 2nd capacitors and diodes to a temperature compensating circuit and varying the resistance value of each diode in accordance with the output voltage of a resistance circuit network including a temperature resistor.

CONSTITUTION: A series circuit of the 1st capacitor 23 and a diode 26 is provided between a surface acoustic wave resonator 16 and an earth together with a series circuit of the 2nd capacitor 24 and a diode 27. The anode power supply voltage is divided by a resistance 21 and applied to the diode 27. The power supply voltage is divided by a heat-sensitive resistor 28 and a resistance 18 and applied to the anode of the diode 26. In such a constitution, the forward voltage corresponding to the temperature is impressed with variation to the diode 26 at a temperature lower than a prescribed level. At the same time, the perfect conduction voltage is applied to the diode 26 at a temperature higher than a fixed level. While the perfect conduction voltage is applied to the diode 27 at a temperature lower than a fixed level; while the forward voltage corresponding to the temperature is impressed with variation to the diode 27 at a temperature higher than a fixed level. Thus it is possible to compensate temperature of a wide range.