In this experiment, an operational amplifier is used as a
voltage comparator. Instead of operating in its
linear amplification region, the op-amp compares an input voltage
with a reference voltage and produces a high or low output.
🎯 Experiment Objectives
Understand the principle of voltage comparison.
Understand the operation of an op-amp comparator.
Study the effect of changing the reference voltage.
Observe HIGH and LOW output states.
Understand threshold detection.
Observe comparator switching behavior.
Relate analog voltage levels to digital-like output states.
👨🎓 Think Before You Start
What happens when Vin is greater than Vref?
What happens when Vin is smaller than Vref?
Why does the output suddenly switch instead of being amplified linearly?
Where can comparator circuits be used in real systems?
📚 1. Theory
What is a Comparator?
A comparator compares two voltages and produces an output
corresponding to which voltage is larger.
For the configuration used in this experiment, the input voltage
is applied to the non-inverting terminal and the reference voltage
is applied to the inverting terminal.
If Vin > Vref → Vout ≈ HIGH
If Vin < Vref → Vout ≈ LOW
Threshold Voltage
The reference voltage acts as the switching threshold. When the
input crosses this threshold, the output changes state.
Comparator Applications
Zero-crossing detectors
Level detectors
Over-voltage protection
Under-voltage detection
Battery monitoring
Light and temperature threshold systems
Analog-to-digital interfaces
Sensor alarm circuits
🧩 2. Virtual Experiment Controls
🟢 Comparator ready. Move Vin across the reference voltage.
🔌 3. Virtual Comparator Circuit
📊 4. Live Measurements
Input Voltage
5.00 V
Reference Voltage
5.00 V
Voltage Difference
0.00 V
Output Voltage
0.00 V
Output State
LOW
Threshold
5.00 V
📈 5. Comparator Switching Characteristic
The graph shows how the comparator output changes when the input
voltage crosses the reference voltage.
🌊 6. Input and Output Waveforms
The comparator converts a continuously varying input into a
two-level output signal.
🔬 7. Engineering Analysis
📝 8. Student Observation Table
Trial
Vin
Vref
Vin − Vref
Output
State
🎓 9. Experiment Conclusion
The operational amplifier can be used as a voltage comparator.
The input voltage is continuously compared with a reference
voltage.
When the input voltage is greater than the reference voltage,
the comparator output switches HIGH.
When the input voltage is lower than the reference voltage,
the comparator output switches LOW.
Therefore, the comparator provides an important bridge between analog sensing and digital decision-making.
❓ 10. Student Quiz
Q1. What is the primary function of a comparator?
Q2. In this experiment, the output becomes HIGH when:
Q3. What determines the switching threshold?
Q4. A comparator can be used for:
Q5. A comparator can help connect:
🤖 CHITTI
GARRF Robotics & Engineering AI Mentor
Use CHITTI to explore comparator circuits, threshold detection,
electronics and engineering applications.
💡 Try asking:
“What is an op-amp comparator?”
“Explain threshold voltage.”
“What happens when Vin crosses Vref?”
“How is a comparator different from an amplifier?”
“Give me real-world applications of comparators.”
👨🎓 11. How to Perform Experiment 13
Observe the virtual comparator circuit.
Set Vref to approximately 5 V.
Set Vin below Vref.
Observe the LOW output state.
Gradually increase Vin.
Watch the output switch when Vin crosses Vref.
Record the switching point.
Change Vref.
Repeat the experiment.
Compare the measured threshold with the selected reference voltage.
⭐ Engineering Challenge
Set the reference voltage to 7 V. Then determine the smallest
input voltage that causes the comparator to change from LOW to
HIGH. Repeat the experiment with a reference voltage of 3 V.
🌍 12. Real-World Engineering Applications
Battery protection:
detecting when battery voltage falls below a safe level.
Temperature alarms:
switching an alarm when a temperature sensor crosses a threshold.
Light detection:
determining whether ambient light is above or below a selected level.
Industrial monitoring:
detecting over-voltage and under-voltage conditions.
Robotics:
converting analog sensor signals into decision signals.
SHM and PZT systems:
threshold-based detection can be used as one stage in signal
conditioning and event detection.
⚠️ Real Laboratory Safety
Important:
This is a virtual experiment. In a physical laboratory,
verify the op-amp pin configuration, power-supply polarity
and voltage limits before energizing the circuit.
Never connect experimental circuits directly to mains voltage.
