PURPOSE: To obtain an oscillation circuit with high stability although the circuit is compact, energy consumption is reduced and cost is lowered by storing the compensation control voltage value of a voltage control oscillator(VCO) corresponding to each temperature as a digital value in an EEPROM, reading the value by an output from a temperature sensor, converting this value to an analog value, and controlling the VCO.

CONSTITUTION: In the oscillation circuit using the VCO, exact temperature compensation is executed by storing the compensation control voltage value of a VCO 5 corresponding to each temperature as the digital value in an EEPROM 3, reading the compensation control voltage value corresponding to each temperature by the output from a temperature sensor 1, converting this value to the analog value, inputting it to the VCO 5 and controlling the VCO 5. For writing the value into the EEPROM 3, it can be easily executed by using a signal, for which the compensation control voltage value to be applied to the VCO 5 is digitized, when phase lock is executed to the output of the VCO 5 to the input of a reference frequency. Thus, while making the circuit compact, reducing the energy consumption and lowering the cost, the stability less than 1ppm can easily be obtained.