Here we show how Phase Shift Oscillator can be constructed using general purpose BC547 transistor. RC phase shift oscillator is one of many method of constructing electronics oscillator. The working principle of RC phase shift oscillator and its design principle was explained in the tutorial BJT Phase Shift Oscillator Online Calculator. Basically RC phase shift oscillator has two block components- one is the amplifier part and the other is the feedback part. The amplifier can be either a transistor or operational amplifier. Here a general purpose transistor the BC547 is used. The feedback part provides the necessary necessary feedback and phase shift of the output oscillating signal. Here a three stage RC high pass filter is used which provides 180 degree phase shift to the transistor output signal at the transistor collector back to the base of the transistor.
The circuit diagram of the BC547 transistor based Phase shift oscillator is shown below.
The above circuit is powered using 6V battery. The oscillating signal appears at the collector of the BC547 transistor. The 10K potentiometer and the resistor R3 is used to bias the transistor in the active region of operation. The capacitors C1,C2,C3,R1, R2 are used to set up the three high pass filter, the feedback network part that shifts the phase of the output signal at the collector by 180 degree. The value of the biasing resistor(the POT) is 3.3kOhm. If the oscillator does not oscillate we can change the POT value to tune to the oscillating frequency of the circuit. The oscillating frequency of this phase shift oscillator is about 62Hz which can be calculated using the online oscillator calculator.
See another variation of BJT transistor phase shift oscillator 2N2222 Phase Shift Oscillator.
