GopalKrishna Advanced Rural Research Foundation

GARRF Virtual Engineering & Electronics Laboratory

KALAM ZERO RESEARCH FUNDING LAB

EXPERIMENT 09 OPERATIONAL AMPLIFIER AMPLIFIERS VIRTUAL LAB

🔬 Experiment 09 — Operational Amplifier Characteristics & Applications

An operational amplifier, commonly called an op-amp, is a high-gain differential voltage amplifier. With appropriate feedback, it can perform amplification, buffering, summing, comparison and many other analog signal-processing functions.

🎯 Experiment Objective

To understand the basic operation of an operational amplifier and experimentally investigate the gain of inverting, non-inverting and voltage-follower configurations.

👨‍🎓 Think Before You Start
  • Why does an op-amp require negative feedback for linear amplification?
  • What determines the gain of an inverting amplifier?
  • Why does a voltage follower have a gain close to unity?
  • What happens when the calculated output exceeds the supply voltage?

📚 1. Theory

Ideal Operational Amplifier

An ideal op-amp has very high open-loop voltage gain, very high input impedance and very low output impedance. It amplifies the difference between its non-inverting and inverting input voltages.

Vout = AOL (V+ − V−)

In practical amplifier circuits, negative feedback is used so that the closed-loop gain is determined mainly by external resistors.

Inverting Amplifier

For an ideal inverting amplifier:

Av = − Rf / Rin

The negative sign indicates approximately 180° phase inversion.

Non-Inverting Amplifier

For an ideal non-inverting amplifier:

Av = 1 + Rf / Rg

The output remains in phase with the input.

Voltage Follower

A voltage follower is a special non-inverting configuration with unity closed-loop gain:

Av ≈ 1

It is useful as a buffer because it presents high input impedance and approximately unity voltage gain.

🧩 2. Select Experiment Configuration

🟢 Ready. Select a configuration and begin.

🔌 3. Virtual Op-Amp Circuit

📊 4. Live Measurements

Vin 0.50 V
Gain −2.00
Ideal Vout −1.00 V
Actual Vout −1.00 V
Rin 10.0 kΩ
Rf 20.0 kΩ
Status LINEAR

📡 5. Input / Output Waveforms

For the inverting amplifier, the output waveform is approximately 180° out of phase with the input. The non-inverting configuration produces an in-phase output.

📈 6. Amplifier Transfer Characteristic

The transfer characteristic shows output voltage as a function of input voltage. The supply voltages limit the practical output swing.

🔬 7. Engineering Analysis

Adjust the input and feedback resistors and observe how the closed-loop gain changes.

📝 8. Student Observation Table

Adjust the controls and click ADD OBSERVATION to record a measurement.

Trial Configuration Vin Gain Vout Status

🎓 9. Experiment Conclusion

The operational amplifier is a high-gain differential amplifier whose practical closed-loop behavior can be controlled using negative feedback.

❓ 10. Student Quiz

Q1. An ideal op-amp has:
Q2. The voltage gain of an ideal inverting amplifier is:
Q3. The output of an ideal voltage follower is approximately:
Q4. Negative feedback is used primarily to:
Q5. If an amplifier attempts to produce a voltage beyond its available supply rails, the output will:

🤖 CHITTI

GARRF Robotics & Engineering AI Mentor

Need help understanding operational amplifiers? Ask CHITTI for guidance.

💡 Try asking:

"What is an operational amplifier?"

"Explain an inverting amplifier."

"Explain a non-inverting amplifier."

"Why does the inverting amplifier have a negative gain?"

"What is a voltage follower?"

"What is negative feedback?"

👨‍🎓 11. How to Perform Experiment 09

  1. Select Inverting Amplifier.
  2. Set Rin and Rf.
  3. Apply a small input voltage.
  4. Observe the calculated gain.
  5. Observe the output voltage and waveform.
  6. Increase the input voltage gradually.
  7. Observe output saturation and clipping.
  8. Repeat using the Non-Inverting Amplifier.
  9. Compare the measured gain with the theoretical gain.
  10. Select Voltage Follower and verify approximately unity gain.
  11. Finally select Comparator and change the reference voltage.
⭐ Engineering Thinking Challenge

If Rf is doubled while Rin remains constant in an inverting amplifier, what happens to the magnitude of the voltage gain?

⚠️ Real Laboratory Safety

Important:

This is a virtual experiment. In a physical op-amp circuit, never exceed the device's specified supply voltage or input common-mode/output limits. Use current limiting and appropriate measurement equipment.