PURPOSE: To enable strong stability against load variation, by the positive feedback of the emitter output of the common collector circuit to the base via the boosting transformer and inserting the crystal oscillator to the feedback circuit.

CONSTITUTION: The emitter output voltage of the transistor 1 is multiplied by winding ratio with the boosting transformer 3 to excite the crystal oscillator 2. The crystal oscillator 2 acts as the series resonator to form the positive feedback loop to the base of the transistor 1 and oscillation is continued with the series resonance frequency of the crystal oscillator 2. The frequency fine tuning circuit 4 is to finely tune the series resonance frequency and it is constituted with capacitors or inductors. Although the oscillation output is picked up from the emitter of the transistor 1, since the output impedance is low, stable oscillation output can be obtained without being affected with greater variation of load.