Question

What is an oscillator? Explain the working of a transistor as an oscillator with a suitable circuit diagram.

Hint:

Transistor oscillators are widely used in generating radio frequencies and other high-frequency signals in communication systems.

Answer 1

Step 1: Definition of Oscillator.
An oscillator is a circuit that generates a continuous periodic waveform (usually sine or squar without requiring an external input signal. The circuit generates its own signal, often referred to as the "oscillations."
Step 2: Working of a Transistor as an Oscillator.
In a transistor oscillator circuit, feedback is used to produce an oscillating signal. A common configuration for a transistor oscillator is the Colpitts oscillator. This type of oscillator uses an LC tank circuit for frequency determination. The feedback network controls the oscillation, ensuring that the transistor amplifies the signal continuously.
The general working of a transistor oscillator:
1. The transistor is used to amplify the signal.
The LC network provides feedback from the output to the input.
3. The feedback loop sustains oscillations, and the circuit generates a stable waveform.

Step 3: Circuit Diagram.
Here’s a simplified circuit diagram for a common emitter oscillator using a transistor: \[ \begin{array}{c} \text{Collector} \ \longrightarrow \text{L} \ \longrightarrow \text{Resistor} \ \longrightarrow \text{Vcc}\\ \ \quad \quad \ \quad \downarrow \\ \quad \text{Base} \longleftarrow \text{Capacitor} \longrightarrow \text{Emitter} \\ \end{array} \] In this diagram, the transistor amplifies the signal, while the LC circuit (inductor and capacitor) sets the frequency of oscillation.
Final Answer:
An oscillator is a circuit that generates a continuous periodic signal. A transistor oscillator uses feedback to sustain oscillations and typically uses an LC tank circuit to determine the frequency.