GopalKrishna Advanced Rural Research Foundation

GARRF Virtual Engineering & Electronics Laboratory

KALAM ZERO RESEARCH FUNDING LAB

EXPERIMENT 21 OP-AMP AMPLIFIER SIGNAL CONDITIONING

🔬 Experiment 21 — Operational Amplifier: Inverting & Non-Inverting Amplifiers

The operational amplifier, commonly called an op-amp, is one of the most useful analog building blocks ever developed. It can amplify, filter, buffer, compare and mathematically manipulate electrical signals.

🎯 Experiment Objectives
  • Understand the basic operation of an operational amplifier.
  • Understand the inverting amplifier configuration.
  • Understand the non-inverting amplifier configuration.
  • Investigate closed-loop voltage gain.
  • Observe phase inversion.
  • Study the effect of resistor ratios on gain.
  • Understand the role of negative feedback.
  • Connect op-amp amplification to sensor signal conditioning.
👨‍🎓 Think Before You Start
  • Why does an op-amp need feedback?
  • Why can changing two resistors change the gain?
  • Why does an inverting amplifier reverse the signal?
  • Why is a non-inverting amplifier useful for sensor signals?

📚 1. What Is an Operational Amplifier?

An operational amplifier is a high-gain differential amplifier. It amplifies the voltage difference between its two input terminals.

Vout ≈ AOL (V+ − V−)

Here AOL is the open-loop gain. In practical amplifier circuits, negative feedback is used to control the overall gain.

Key engineering principle:

Negative feedback allows a very high-gain device to become a predictable and useful amplifier.

🔄 2. Negative Feedback

Instead of allowing the enormous open-loop gain of an op-amp to determine the output directly, part of the output is fed back to the inverting input.

# Closed-loop gain Predictable resistor relationship

This is one of the most important ideas in analog electronics.

⚙️ 3. Virtual Experiment Controls

🟢 Op-amp ready.

🔌 4. Virtual Circuit

📊 5. Live Results

Input 100 mV
Gain −5.00×
Output −0.50 V
Phase 180°
Frequency 1000 Hz
Supply ±12 V
Headroom 11.50 V
Status LINEAR

📈 6. Input and Output Waveforms

Blue represents the input signal. Green represents the op-amp output. The inverting configuration produces a 180° phase reversal.

📐 7. Gain Equations

Inverting: Av = − Rf / Rin
Non-Inverting: Av = 1 + Rf / Rin
Remember:

The negative sign in the inverting configuration does not mean that the amplifier produces negative energy. It indicates a phase reversal of the voltage signal.

🔬 8. Engineering Analysis

🧪 9. Investigate Negative Feedback

Perform the following virtual investigations.

  1. Set Rin = 10 kΩ.
  2. Set Rf = 10 kΩ.
  3. Observe the gain.
  4. Increase Rf to 50 kΩ.
  5. Observe how the gain changes.
  6. Switch to the non-inverting configuration.
  7. Compare the gain with the same resistor values.
Challenge:

Can you design an amplifier with a gain of approximately 10×?

🧠 10. Virtual Experiment Challenge

Try to obtain the following conditions:

Target Requirement
Gain Approximately 10×
Input 100 mV
Output Approximately 1 V
Operation Linear
Distortion Minimal

Choose appropriate resistor values and configuration.

🎯 Challenge not yet evaluated.

🧪 11. Student Observation Table

Trial Configuration Vin Rin Rf Gain Vout Phase

🎓 12. Experiment Procedure

  1. Select the inverting amplifier.
  2. Set Vin to 100 mV.
  3. Set Rin to 10 kΩ.
  4. Set Rf to 50 kΩ.
  5. Observe the calculated gain.
  6. Observe the input and output waveforms.
  7. Change Rf and record the results.
  8. Switch to the non-inverting configuration.
  9. Repeat the experiment.
  10. Increase input amplitude until clipping occurs.
  11. Investigate the effect of frequency.

📡 13. Why Op-Amps Matter for Sensors

Many sensors produce signals that are too small, noisy or unsuitable for direct connection to a microcontroller ADC.

An op-amp can be used to provide:

💡 PZT / SHM Research Connection

A PZT sensor used for structural health monitoring can produce dynamic electrical signals associated with mechanical vibration, wave propagation or structural response.

Analog signal conditioning is often required before such signals are digitized and processed by an ADC, computer or AI system.

Thus, this simple op-amp experiment provides an important conceptual bridge from electronics → sensors → SHM → data acquisition → AI.

🌍 14. Real-World Applications

❓ 15. Student Quiz

Q1. An op-amp has how many primary signal terminals?
Q2. The gain of an inverting amplifier is:
Q3. The output of an inverting amplifier is:
Q4. Negative feedback generally makes the amplifier gain:
Q5. An op-amp can be useful for:

🤖 CHITTI

GARRF Robotics & Engineering AI Mentor

Ask CHITTI about operational amplifiers, signal conditioning, robotics electronics, sensors and analog circuits.

💡 Try asking:

“Why does an inverting op-amp have a negative gain?”

“What is negative feedback?”

“How can I design a gain of 10?”

“Why are op-amps useful for PZT sensors?”

“What is the difference between an inverting and non-inverting amplifier?”

⚠️ 16. Physical Laboratory Safety

Important:

This is an educational virtual simulation. For a physical circuit, always verify the op-amp supply voltage, pin configuration and component ratings before powering the circuit.

Never connect experimental electronics directly to mains voltage.

🎓 17. Experiment Conclusion

The operational amplifier is one of the fundamental building blocks of analog electronics. By using negative feedback, the designer can create a predictable amplifier whose gain is primarily determined by external components.

The experiment demonstrates how a simple resistor network can control amplification and how analog electronics can prepare sensor signals for measurement, digitization and intelligent processing.

From transistor amplification to precision signal conditioning — the op-amp is a gateway to modern instrumentation.