Coupling Capacitor Signal Transmission Experiment

Objective

The purpose of this experiment is to demonstrate the use of a coupling capacitor to transmit AC signals while blocking DC components in a circuit. This is useful in many analog circuits, such as audio signal processing.

Components Required

• 1 x Coupling Capacitor (0.1µF or 1µF)
• 1 x Function Generator (for AC signal input)
• 1 x Oscilloscope (for signal observation)
• 1 x DC Voltage Source (e.g., 5V)
• Connecting Wires
• Breadboard
• Resistors (10kΩ)

Theory

A coupling capacitor is commonly used to transmit AC signals between different stages of a circuit while blocking the DC component. Capacitors allow AC to pass through by charging and discharging in sync with the AC signal, but they prevent DC signals from passing because DC voltage does not change over time, resulting in no charge movement.

Circuit Diagram

Experimental Setup

1. Connect the function generator to one end of the coupling capacitor.

2. The other end of the capacitor connects to a 10kΩ resistor, which is connected to ground.

3. Place the oscilloscope probe at the node between the capacitor and resistor to measure the signal.

4. Additionally, connect a DC voltage source (e.g., 5V) to the input to simulate a DC offset in the signal.

Procedure

1. Set the function generator to output a sine wave of 1kHz frequency and 1V peak-to-peak amplitude.
2. Observe the input signal using the oscilloscope before the capacitor. You should see both the AC signal and the DC offset.
3. Now, measure the signal after the coupling capacitor at the resistor. Notice that the DC component is blocked, and only the AC signal is transmitted.
4. Change the frequency of the sine wave and observe how the output signal changes. Higher frequencies will pass through with less attenuation.

Results and Observations

The coupling capacitor allows the AC signal to pass while blocking the DC offset. The oscilloscope should show a clean sine wave at the output with no DC voltage. By varying the frequency, you can observe how the capacitor attenuates lower frequencies, with higher frequencies passing through more easily.

Conclusion

In this experiment, we demonstrated the ability of a coupling capacitor to transmit AC signals while blocking DC components. This is an important feature in signal processing and analog circuits where AC signals need to be transferred between stages without affecting the DC biasing of the circuit.