An oscillation circuit having a piezoelectric vibrator (X) such as a quartz crystal, oscillation capacitors (C1, C2) and a feedback amplification transistor (TR) comprises a constant-current source (I) connected in series with the emitter of the transistor (TR). The negative resistance of the oscillation circuit is substantially increased, and the oscillation rise time required for the oscillation output to be brought into an oscillation state at a prescribed output voltage level and a prescribed oscillation frequency after the application of the power voltage can be shortened.
