Band-Pass Filter Experiment

Objective

The objective of this experiment is to design and analyze a band-pass filter (BPF) that allows frequencies within a certain range to pass while attenuating frequencies outside that range. This experiment will demonstrate the functionality and application of band-pass filters in signal processing.

Components Required

• 1 x Resistor (R1)
• 1 x Resistor (R2)
• 1 x Capacitor (C1)
• 1 x Capacitor (C2)
• 1 x Operational Amplifier (e.g., LM358)
• 1 x Signal Generator
• 1 x Oscilloscope
• Connecting Wires
• Breadboard (optional)

Theory

A band-pass filter is an electrical circuit that passes frequencies within a certain range and attenuates frequencies outside that range. The filter is created using a combination of resistors and capacitors that form low-pass and high-pass filters in series.

The cutoff frequencies, \( f_L \) (lower cutoff) and \( f_H \) (upper cutoff), can be determined using the following formulas:

• Lower Cutoff Frequency: \( f_L = \frac{1}{2 \pi R_1 C_1} \)
• Upper Cutoff Frequency: \( f_H = \frac{1}{2 \pi R_2 C_2} \)

Circuit Diagram

Experimental Setup

1. Connect the components according to the circuit diagram, ensuring all connections are secure.

2. Connect the output of the signal generator to the input of the band-pass filter.

3. Connect the output of the band-pass filter to the input of the oscilloscope.

Procedure

1. Set up the circuit according to the circuit diagram.
2. Configure the signal generator to produce a sine wave at a specific frequency.
3. Observe the output signal on the oscilloscope and record its amplitude and waveform.
4. Vary the input frequency and note how the output signal changes as it approaches the cutoff frequencies.
5. Record the amplitude of the output signal at various input frequencies, particularly near the cutoff frequencies.
6. Determine the lower and upper cutoff frequencies based on your observations.

Results and Observations

Document the output signal amplitude and characteristics for different input frequencies. Note the frequencies at which the output signal begins to attenuate and the band-pass range.

Conclusion

This experiment demonstrates the operation of a band-pass filter, highlighting its ability to allow a specific range of frequencies to pass while attenuating others. Band-pass filters are widely used in applications such as audio processing, radio communications, and instrumentation.