How to Use LM386: Examples, Pinouts, and Specs

The LM386 is a low-voltage audio power amplifier designed for use in low-power applications. It is capable of driving small speakers and headphones, making it ideal for portable and battery-powered devices. With a default gain of 20, which can be increased up to 200 using external components, the LM386 is versatile and widely used in audio amplification circuits.

• Portable audio devices
• Battery-powered amplifiers
• Intercom systems
• AM/FM radio amplifiers
• DIY audio projects
• Signal amplification for small speakers or headphones

The LM386 is a compact and efficient amplifier with the following key specifications:

The LM386 is an 8-pin IC with the following pinout:

1. Power Supply: Connect Pin 6 (Vcc) to a power source between 4V and 12V, and Pin 4 (GND) to ground.
2. Input Signal: Feed the audio signal to Pin 3 (Non-Inverting Input). Pin 2 (Inverting Input) is typically connected to ground.
3. Output Signal: Connect Pin 5 to the speaker or headphone. Use a coupling capacitor (e.g., 220 µF) to block DC components.
4. Gain Adjustment: To increase the gain, connect a capacitor (e.g., 10 µF) between Pins 1 and 8. For the default gain of 20, leave these pins unconnected.
5. Bypass Capacitor: Connect a capacitor (e.g., 10 µF) to Pin 7 to reduce noise and improve stability.

Below is a basic LM386 amplifier circuit:

   +Vcc (4V-12V)
       |
       +----[10 µF]---- Pin 7 (Bypass)
       |
      Pin 6 (Vcc)
       |
      Pin 4 (GND) ------------------ Ground
       |
Audio Input ----[10 kΩ]---- Pin 3 (Non-Inverting Input)
       |
      Pin 2 (Inverting Input) ---- Ground
       |
      Pin 5 (Output) ----[220 µF]---- Speaker/Headphone
       |

The LM386 can be used with an Arduino UNO to amplify audio signals. Below is an example of generating a simple tone:

/*
  Example: Generating a tone using Arduino and LM386
  This code generates a 1 kHz square wave on Pin 9, which can be amplified
  using the LM386. Connect Pin 9 to the LM386's input (Pin 3).
*/

const int tonePin = 9; // Pin connected to LM386 input

void setup() {
  pinMode(tonePin, OUTPUT); // Set Pin 9 as output
}

void loop() {
  // Generate a 1 kHz square wave
  digitalWrite(tonePin, HIGH);
  delayMicroseconds(500); // 500 µs HIGH for 1 kHz
  digitalWrite(tonePin, LOW);
  delayMicroseconds(500); // 500 µs LOW for 1 kHz
}

• Use decoupling capacitors (e.g., 0.1 µF) near the power supply pins to reduce noise.
• Avoid exceeding the maximum supply voltage (12V) to prevent damage.
• Use a heatsink if the IC gets too hot during operation.
• Ensure proper grounding to minimize noise and interference.

1. No Output Signal:

   • Check the power supply connections (Pin 6 and Pin 4).
   • Verify that the input signal is connected to Pin 3.
   • Ensure the speaker or headphone is properly connected to Pin 5.

2. Distorted Output:

   • Reduce the input signal amplitude to avoid overdriving the amplifier.
   • Check the gain configuration (Pins 1 and 8) and ensure it is appropriate for your application.
   • Use a bypass capacitor on Pin 7 to reduce noise.

3. Excessive Noise:

   • Add a decoupling capacitor (e.g., 0.1 µF) near the power supply pins.
   • Ensure proper grounding and minimize long wires in the circuit.

4. Overheating:

   • Check the load impedance (should not be less than 8Ω).
   • Reduce the supply voltage if it is near the maximum limit.

Q: Can the LM386 drive a 4Ω speaker?
A: While the LM386 is designed for 8Ω loads, it can drive a 4Ω speaker at lower volumes. However, this may cause overheating, so it is not recommended for prolonged use.

Q: How do I increase the gain of the LM386?
A: Connect a capacitor (e.g., 10 µF) between Pins 1 and 8 to increase the gain up to 200.

Q: What is the purpose of the bypass capacitor on Pin 7?
A: The bypass capacitor reduces noise and improves the stability of the amplifier.

Q: Can I use the LM386 with a 3.3V power supply?
A: No, the minimum supply voltage for the LM386 is 4V. Using a lower voltage may result in improper operation.