Question

Explain the working of oscillating process of a transistor, with the help of circuit diagram.

Hint:

Oscillator = Amplifier + Positive Feedback + LC/RC tank circuit.

Answer 1

Step 1: Principle.
A transistor oscillator works on the principle of positive feedback. The output of an amplifier is fed back to its input in phase to maintain continuous oscillations.
Step 2: Essential components.
- A transistor amplifier.
- Feedback network (usually LC tank circuit).
- DC power supply.
Step 3: Working process.
1. When supply is given, noise voltage in the circuit provides initial signal.
2. The LC tank circuit produces oscillations of its natural frequency.
3. The transistor amplifies these oscillations.
4. A part of output is fed back in phase with the input, reinforcing it.
5. Continuous undamped oscillations are maintained.
Step 4: Barkhausen criterion.
For sustained oscillations: \[ \text{Loop gain} = A \beta = 1. \]
Step 5: Circuit diagram.
(Insert diagram of transistor oscillator: LC tank circuit at input, transistor amplifier, feedback loop).
Step 6: Conclusion.
Thus, a transistor oscillator converts DC power into continuous AC output of a desired frequency.