PURPOSE: To obtain a stable phase locking state by using a voltage obtained by correcting an output voltage of a reference voltage generator in accordance with the change on the ambient temperature to as a reference voltage, and feeding back negatively a signal being the result of voltage sum of an output error signal of a frequency phase comparator and an output analog signal of a digital analog converter to a voltage controlled oscillator.

CONSTITUTION: A temperature compensation voltage conversion section 9 is provided between a digital analog converter 3 and a reference voltage generator 2. A temperature compensation voltage conversion section 9 corrects and outputs an input voltage from the reference voltage generator 2 into a required value in response to the change in the ambient temperature and consists of a sensister or thermister. When the characteristic of the voltage versus oscillated frequency of the voltage controlled oscillator 8 changes due to the ambient temperature change, the temperature compensation type voltage converter 9 is operated and corrected in response to the temperature change with respect to the output voltage of the reference voltage generator 2. Thus, stable phase lock state is obtained against ambient temperature change even at a high frequency range.