PURPOSE: To enable to expect the stable operation with ease of adjustment, by realizing the compensation of non-linear characteristics with a simple detection circuit and a digital control circuit.

CONSTITUTION: The analog detection output of the temperature detection circuit 1 constituted with thermisters is in digital-conversion with the A/D conversion circuit 2 and it is inputted to the control circuit 3. The control circuit 3 reads in the control method from the memory circuit 4 with the input. The control method preset is written in the memory circuit 4. The control circuit 3 controls the compensation signal output circuit 5 with the content of the memory circuit 4 and generates the compensation signal. This compensation signal is the bias for the crystal oscillator 6 and the varactor 7 in series connection.