Non-Inverting Amplifier Using LM358

A non-inverting amplifier is a widely used operational amplifier (op-amp) configuration that amplifies an input signal without inverting its phase. The LM358 is a popular dual op-amp IC used in low-power and general-purpose applications.

1. Understanding the Non-Inverting Amplifier

✅ Key Features:

• Amplifies the input signal without phase inversion.
• Gain is controlled using two resistors.
• High input impedance, making it ideal for signal processing.

❌ Limitations:

• Output voltage is limited by the power supply range.
• Not suitable for high-frequency applications (better for low-to-mid frequencies).

2. Circuit Diagram

Components Required:

1. LM358 Op-Amp (or any general-purpose op-amp)
2. Resistors:
   • R1​ (Feedback Resistor)
   • R2 (Ground Resistor)
3. Power Supply (5V – 15V)
4. Input Signal Source
5. Output Load (e.g., Speaker, ADC input, etc.)

Circuit Configuration:

• Non-inverting input (+): Connected to the signal source.
• Inverting input (-): Connected to the voltage divider formed by R1​ and R2​.
• Output: Connected to the load.

Where:

• R1​ = Feedback resistor
• R2​ = Resistor to ground

3. Gain Calculation

The voltage Gain (Av) of a non-inverting amplifier is given by:

Example:

If:

• R1=100kΩ
• R2=10kΩ

This means the output voltage is amplified 11 times compared to the input.

4. Practical LM358 Circuit (5V Power Supply)

Connections:

1. Power: Connect Vcc (Pin 8) to +5V and GND (Pin 4) to ground.
2. Input Signal (Vin): Connect to non-inverting input (+) (Pin 3).
3. Feedback Resistors:
   • R1​ (Feedback Resistor, 100kΩ) connects Pin 1 (Output) to Pin 2 (- Input).
   • R2​ (10kΩ) connects Pin 2 (- Input) to ground.
4. Output (Vout): Take output from Pin 1.

Pin Configuration of LM358

5. Advantages of Non-Inverting Amplifier

✔ High Input Impedance → Does not load the source.
✔ Stable Gain → Easily adjustable with two resistors.
✔ No Phase Inversion → Output is in the same phase as input.
✔ Used in Sensors, Audio, ADC buffers, and Signal Processing.

6. Applications of LM358 Non-Inverting Amplifier

📌 Audio Signal Amplification (Microphone preamps, headphones)
📌 Signal Conditioning for Sensors (Temperature, light, pressure sensors)
📌 Voltage Level Shifting for ADC inputs
📌 Buffer Amplifier in Control Circuits

7. Limitations & Considerations

• Output swing is limited → LM358 cannot reach full supply voltage.
• Low bandwidth → Not suitable for high-frequency applications.
• Not ideal for high-precision applications → Use TL072 or OPA2134 for better performance.

8. Alternative Op-Amps

Conclusion

The non-inverting amplifier with LM358 is a versatile and easy-to-use circuit for many electronics projects. It provides signal amplification with a stable gain, making it useful in audio, sensors, and general signal processing.