13-09-2013, 02:35 PM
COLPITTS OSCILLATOR
Aim:
To design and construct the given oscillator at the given operating frequency.
Theory:
A Colpitts oscillator is the electrical dual of a Hartley oscillator. In the Colpitts
circuit, two capacitors and one inductor determine the frequency of oscillation. The
oscillator derives its initial output from the noise signals present in the circuit. After
considerable time, it gains strength and thereby producing sustained oscillations. It has
two major parts namely – amplifier part and feedback part. The amplifier part has a
typically CE amplifier with voltage divider bias. In the feedback path, there is a CLC
network. The feedback network generally provides a fraction of output as feedback.
Procedure:
1. Rig up the circuit as per the circuit diagrams (both oscillators).
2. Switches on the power supply and observe the output on the CRO (sine wave).
3. Note down the practical frequency and compare with its theoretical frequency.
Result:
Thus Colpitts oscillator is designed and constructed and the output sine wave
frequency is calculated as