22-02-2013, 11:58 AM
To design Band pass filter using OPAMP and to plot its frequency response.
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OBJECTIVE: -To design Band pass filter using OPAMP and to plot its frequency response.
(I) PRACTICAL SIGNIFICANCE: - Band pass filter is used in communication receivers like AM & FM receiver.
(II) COMPETENCY/SKILL: - Design and testing.
(III) EXPERIMENT OBJECTIVE: -To design Band pass filter using OPAMP and to plot its frequency response.
(IV) THEORETICAL BACKGROUND: -
A band pass filter has a pass band between two cutoff frequencies fH and fL such that fH>fL. Any input frequency outside this pass band is attenuated.A band pass filter is useful when you want to tune in a radio or television signal. It is also useful in telephone communications equipment for separating the different phone conversations that are being simultaneously transmitted over the same communication path. Fig. Shows the ideal frequency response of a band pass filter. A brick wall response like this blocks all frequencies from zero up to the lower cutoff frequency. Then it passes all the frequencies between the lower and upper cutoff frequency. Finally it blocks all frequencies above the upper cut off frequency.
The bandwidth of a band pass filter is the difference between its upper and lower 3 db cutoff frequencies. The Q of a band pass filter is defined as the center frequency divided by the bandwidth. The center frequency is symbolized by fO and is given by the geometric average of the two cutoff frequencies: fO = √fLfH. Thus Q is a measure of selectivity. A filter is said to be wide band pass if it’s Q<10 and narrow band pass if it’s Q>10.
NARROW BAND-PASS FILTER
The narrow band-pass filter using multiple feedbacks is in Figure. As shown in this figure, the filter uses only one op-amp. Compared to all the filers discussed so far, this filter is unique in the following respects;
1. It has two feedback paths, hence the name multiple-feedback filter.
2. The op-amp is used in the inverting mode.
Generally, the narrow band-pass filter is designed for specific values of center frequency fC and Q or fC and bandwidth.
PROCEDURE: -
1. Now connect the circuit as per diagram.
2. Apply 1Vp-p sinusoidal as 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. to rectifier.
5. Calculate voltage gain and tabulate the reading as per observation table.
6. Plot the frequency response curve for the filter and find out the cut off frequency of the filter.
(XII) CONCLUSION:
We studied the design of Narrow Band Pass Filter. Also verified the calculated and observed frequency response of designed filters.