LM380 Audio Power Amplifier Circuit And it’s Working

The LM380 is a popular audio power amplifier IC, designed for delivering low-distortion audio amplification with a wide range of input signals. It’s often used in DIY audio projects due to its simplicity and robust performance. This IC can drive speakers directly, making it ideal for small audio applications like radio receivers, intercoms, and phonographs.

Features of LM380 Audio Power Amplifier IC

• Power Output: The LM380 can deliver up to 2.5 watts of power output, sufficient for small speakers.
• Wide Supply Voltage Range: It operates with a power supply voltage between 10V and 22V.
• Low Distortion: With low harmonic distortion, it provides clear audio output.
• Thermal Protection: The IC includes thermal shutdown protection, preventing damage due to overheating.
• Internal Biasing: The IC has built-in biasing resistors, reducing external component count.
• Single or Split Power Supply: It can be operated with either a single power supply or dual (split) power supplies.
• Built-in Voltage Gain: The IC comes with a built-in voltage gain of 34dB, which can be adjusted using external components.

LM380 IC Pinout Diagram

The LM380 is available in an 8-pin or 14-pin dual inline package (DIP). Below is the pinout diagram for the 8-pin version:

• Pin 1, 8: Input pins connected to the audio signal source.
• Pin 2, 7: Ground pins connected to the common ground of the circuit.
• Pin 3: Negative supply voltage (V-).
• Pin 4, 5: Output pins connected to the speaker or load.
• Pin 6: Positive supply voltage (V+).

Pin Description of 8-Pin LM380 IC

1. Pin 1 (Input): This is the non-inverting input where the audio signal is fed.
2. Pin 2 (Ground): This pin is connected to the ground of the circuit.
3. Pin 3 (V-): This pin is connected to the negative power supply.
4. Pin 4 (Output): This pin is connected to the load (speaker).
5. Pin 5 (Output): Another output pin connected to the load, working in conjunction with Pin 4.
6. Pin 6 (V+): This pin is connected to the positive power supply.
7. Pin 7 (Ground): Similar to Pin 2, this is connected to the ground of the circuit.
8. Pin 8 (Input): This is the inverting input where the reference ground or feedback network is connected.

Phono Amplifier Using LM380 IC

The LM380 can be configured as a phono amplifier to amplify the low-level signals from a phonograph (turntable). The phono amplifier typically includes an equalization network to correct the frequency response of the signal, ensuring accurate sound reproduction. The LM380’s low distortion and good signal-to-noise ratio make it suitable for this application, providing clear and natural audio output.

Bridge Amplifier Using LM380 IC

A bridge amplifier configuration using two LM380 ICs can be used to double the output power. In this configuration, one LM380 IC amplifies the signal normally, while the second IC inverts the signal and then amplifies it. The speaker is connected between the two outputs, effectively doubling the voltage across the speaker, resulting in higher output power. This setup is useful in applications where more power is required without increasing the supply voltage.

Applications of LM380 Audio Power Amplifier IC

• Portable Audio Devices: Used in radios, intercoms, and other small audio equipment.
• Phonograph Amplifiers: Amplifies signals from turntables for better audio output.
• Headphone Amplifiers: Can drive headphones directly for personal audio devices.
• Public Address Systems: Used in small PA systems for amplifying voice signals.
• Signal Boosters: Used to boost low-level audio signals in various applications.
• TV Sound Systems: Amplifies audio in television sets for better sound quality.

Conclusion

The LM380 is a versatile audio power amplifier IC that is easy to use in a variety of applications. Its ability to deliver clean, low-distortion audio with minimal external components makes it a favorite among hobbyists and professionals alike. Whether used in phono amplifiers, bridge amplifiers, or other audio circuits, the LM380 provides reliable performance with simplicity.