1. A piezoelectric oscillator comprising a transistor, wherein:
one end of a resonant circuit is connected to a gate of the transistor;
another end of the resonant circuit is grounded via a resistor;
an output terminal is provided for a drain of the transistor;
a piezoelectric resonator for causing reflection by resonance is connected to a source of the transistor;
the piezoelectric resonator serving as a reflective element resonates by use of reflection characteristics and output an oscillation
the oscillation frequency of the piezoelectric resonator and a resonance frequency of the resonant circuit are set to substantially
the same frequency.