RC Phase Shift Oscillator
The RC phase-shift oscillator consists of a single transistor in the ‘Common Emitter’ configuration and a phase-shift section consisting of three sections of RC combination. Each resistor and capacitor combination provides a phase shift of 60 degrees to the signal. As there are three sections of RC, the total phase shift will be 180 degrees. The transistor also provides a phase shift of 180o to the input signal. Therefore, the total phase shift is 360o in the circuit.
The frequency of oscillations produced by an RC phase shift oscillator is given by:
Fo = 1/(2πRC𢆦) where
R = R1 = R2 = R3
C = C1 = C2 = C3
The RC phase-shift oscillator generates sinusoidal waves with frequency Fo = 1/(2πRC𢆦).
Examples of other commonly used oscillators include:
- Wein Bridge Oscillator
- Hartley Oscillator
- Colpitts Oscillator
- Crystal Oscillator
Applications:
Some uses of the oscillators include:
- Electronic devices like computers have microprocessors that work on clock pulses. The oscillators provide these clock pulses.
- Signal generators generate different signals which are used in laboratories.
- Day-to-day devices like TV, computers, Inverters, Audio, Video systems, etc.
- Metal detectors, Quartz watches.
Frequently asked questions:
1. What is the total phase shift of a signal in an oscillator circuit?
Ans) The total phase shift of an input signal across the loop (i.e. from input to output, from output to feedback element, from feedback element to input signal) must be equal to 0 degrees or 360 degrees.
2. What is the significance of feedback factor ‘β’?
Ans) Feedback factor represents the portion of output signal which is fed back as input to the system. The value of β changes from system to system.
3. What is the role of thermal noise in oscillators?
Ans) Any unwanted disturbance in an electronic system is termed as ‘Noise’. Thermal noise is the unwanted signal generated in a system because of the excitations and de-excitation of charge carriers in the system. This thermal noise itself is sufficient for an oscillator to generate oscillating signals.