22-02-2013, 11:46 AM
To design a LPF using R & C and to study its characteristics
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OBJECTIVE: - To design a LPF using R & C and to study its characteristics
(I) PRACTICAL SIGNIFICANCE: - Low pass filters are used in communication system for obtaining original message signal .LPF is used in AM and FM receiver.
(II) COMPETENCY/SKILL: - Design and testing.
(III) EXPERIMENT OBJECTIVE: - To design a LPF using R & C and to study its characteristics
(IV) THEORETICAL BACKGROUND: -
The low pass filter uses an RC network for filtering. The low pass filter has a constant gain A. The frequency at which gain is 3 dB is known as the cutoff frequency fC., and after fC it decreases at constant rate with an increase in frequency. That is when the frequency is increased tenfold (one decade), the voltage gain is divided by 10. In other words, the gain decreases 20db (=20 log 10) each time the frequency is increased by 10. Hence the rate at which the gain rolls of after fc is 20db/decade.
PROCEDURE: -
1. Now connect the circuit as per diagram.
2. Apply sinusoidal input signal of constant amplitude (Vin) to the input terminal of the circuit.
3. Vary the input frequency from 10 Hz (keep Vin constant) in steps & note corresponding peak to peak amplitude of output (Vo).
4. Calculate voltage gain and tabulate the reading as per observation table.
5. Plot the frequency response curve for the filter and find out the cut off frequency of the filter.