Pierce oscillator is a variant of Colpitts oscillator in which instead of inductor a quartz crystal is used. Crystal based oscillator like Pierce oscillator are stable oscillator that are used as RF oscillator in RF communication circuits. The basic working principle of Pierce crystal oscillator is similar to that of Colpitts oscillator and this was explained in details in How Pierce crystal oscillator Works. In this blog post, a variant of the basic Pierce crystal oscillator is illustrated wherein the two capacitors typically found in basic Pierce oscillator are not used. Instead the internal capacitance of bipolar transistor(BJT) are used for forming the feedback filter along with the crystal.
The following picture shows the 2N2222 bipolar transistor based Pierce crystal oscillator constructed on a breadboard shown in the above circuit diagram.
The following shows circuit diagram of the above bipolar junction transistor(BJT) based Pierce crystal oscillator which uses the internal capacitance of the transistor.
Video demonstration
The following video shows the BJT based Pierce crystal oscillator working on a breadboard.
Such Pierce oscillator can be used in RF circuits such as in AM modulator, AM demodulator circuits, FM circuits and others where it generates local oscillator signals. Moreover it can also be used in beat frequency oscillator(BFO) circuits to generate stable signal.
References:
[1] 2N5550 Colpitts Oscillator
[2] Drain Feedback biased E-MOSFET Colpitts Oscillator
[3] Colpitts oscillator with LM358 and TL072 Op-Amps
