PURPOSE: To entirely exclude a disadvantage resulting from a change in a Q of an LC circuit A even when the Q of the LC circuit A changes due to a change in an ambient temperature.

CONSTITUTION: A current of a constant current circuit B is fed to an LC circuit A and an output of the LC circuit A is subject to positive feedback amplification by using a positive feedback amplifier circuit D, then the LC circuit A is oscillated stably and continuously. When the Q of the LC circuit A changes due to ambient temperature, the loop gain of the positive feedback amplifier circuit D is adjusted by a temperature compensation circuit E having a negative temperature characteristic according to the change. As a result, the entire loop gain is made stable against the ambient temperature. Although the temperature compensation circuit E has a negative temperature characteristic, since a VD multiplier circuit is employed, the temperature coefficient of the temperature compensation circuit E is simply changed by having only to change the circuit constant.