To prevent a phase noise from being increased for a temperature compensation crystal oscillator while realizing low power consumption of the temperature compensation crystal oscillator.

A constant voltage generating circuit 10 to drive a temperature compensation crystal oscillation circuit 1 consists of a differential amplifier circuit 5, a DC load 7 that applies a feedback signal to the differential amplifier circuit 5, a driver 9 using a control signal outputted from the differential amplifier circuit 5 to drive the DC load 7 and the temperature compensation crystal oscillation circuit 1, and a low pass filter 13 consisting of passive components to eliminate a high frequency component from the control signal and to apply the resulting control signal to the driver 9.