Comparator Voltage Level Experiment

Introduction

This experiment demonstrates how a comparator circuit compares two input voltages and generates a high or low output depending on which voltage is greater. Comparators are essential in many applications such as zero-crossing detectors, analog-to-digital conversion, and signal level detection.

Objective

The objective is to construct a basic comparator circuit using an operational amplifier (op-amp) and observe its output response as the input voltage changes relative to a reference voltage.

Components Required

• Operational Amplifier (e.g., LM358 or similar)
• Two 10kΩ Resistors
• Variable Resistor (Potentiometer) - 10kΩ
• Power Supply (5V or 9V)
• LED (optional, for output indication)
• Breadboard and connecting wires
• Multimeter (for voltage measurement)
• Oscilloscope (optional, for visualizing output waveforms)

Circuit Diagram

Note: The circuit consists of an op-amp with two inputs: inverting and non-inverting. The output is connected to an LED for indication. One input receives a fixed reference voltage, and the other is controlled by a variable input voltage.

Procedure

1. Build the Circuit: Construct the comparator circuit on a breadboard. Apply a reference voltage to the inverting input using a resistor divider, and connect the non-inverting input to the potentiometer to control the variable voltage.
2. Adjust the Input Voltage: Vary the potentiometer to change the input voltage at the non-inverting input of the op-amp. Observe the output as the voltage crosses the reference voltage threshold.
3. Monitor Output: When the input voltage rises above the reference voltage, the op-amp output will switch to the high state (or low, depending on the op-amp configuration). The LED will indicate this switch by turning on or off.
4. Optional - Use Oscilloscope: Connect an oscilloscope to observe the input and output waveforms in real-time, allowing you to see the exact switching behavior of the comparator.

Observations and Analysis

• When the input voltage is below the reference voltage, the output remains in one state (e.g., low in an inverting comparator setup).
• As the input voltage exceeds the reference voltage, the output switches to the opposite state (e.g., high).
• The exact switching point, or threshold, depends on the reference voltage applied to the inverting input.

Conclusion

This experiment successfully demonstrates the use of a voltage comparator circuit. By setting a reference voltage, the comparator can detect when an input voltage crosses this threshold, providing a simple digital output. This technique is useful in a wide variety of applications, such as signal processing and level detection.