DIY Speaker ampifier with lm368

Let's build a mini audio amplifier using the LM386 IC. This will help you understand the basics of audio amplification.

Components

• breadboard,
• LM386 audio amplifier IC,
• a battery and connector,
• 0.1 microfarad capacitor,
• 1, 000 microfarad capacitor
• potentiometer
• audio jack
• a small 8-ohm 1-watt speaker
• a 10 ohm resistor.

First, let's understand the LM386 IC

Understanding the LM386 Audio Amplifier IC

When it comes to building simple and low-power audio amplifier circuits, one of the most popular ICs among hobbyists and engineers is the LM386. Compact, easy to use, and inexpensive, this chip is a go-to solution for small speaker projects, radios, toys, and DIY audio gadgets.

What is the LM386?

The LM386 is a low-voltage audio power amplifier IC designed to drive small speakers (like 8Ω or 4Ω). It operates with a supply voltage as low as 4V and up to 12V (or 18V in some variants), which makes it suitable for battery-powered devices.

Key highlights:

• Output power: ~0.5W at 8Ω, 9V supply
• Designed for low distortion
• Minimal external components required
• Adjustable gain (20 to 200)

Pin Configuration

The LM386 comes in an 8-pin DIP package. Here’s what the pins do

• Gain 1 (Pin 1) – Connects to Pin 8 via a capacitor to increase gain.
• - Input (Pin 2) – Inverting input.
• + Input (Pin 3) – Non-inverting input
• GND (Pin 4) – Ground connection.
• Output (Pin 5) – Amplified audio signal output to speaker.
• Vcc (Pin 6) – Power supply (4–12V typically)
• Bypass (Pin 7) – Used with a capacitor for noise reduction.
• Gain 2 (Pin 8) – Works with Pin 1 to adjust gain.

How the Gain Works

By default, the LM386 has a gain of 20. If you connect a capacitor (typically 10 µF) between Pins 1 and 8, the gain increases up to 200. This feature makes the chip flexible for different audio levels.

• No capacitor (Pins 1 & 8 open): Gain = 20
• With 10 µF capacitor between Pins 1 & 8: Gain = 200

You can use a potentiometer to adjust the volume

• Pin 3 of the LM386 is the non-inverting input. That's where our audio signal goes through the potentiometer to adjust the volume.
• Pin 2 is the inverting input connected to the ground.
• Pin 6 is VCC, we will connect 9 volt here.
• Pin 4 is the ground.
• Pin 5 is the output connected to the speaker through a 1000 microfarad capacitor. This capacitor blocks DC and only allows AC audio signals to pass.

• Pins 1 and 8 control the gain. By default, the LM386 has a gain of 20. Adding a 10 microfarad capacitor between pins one and 8 can increase it to 200.
• Pin 7 is the bypass pin where we add a capacitor to reduce the noise.

This is a very basic circuit, and sure it has got some problems like distortion and all but you can actually improve this circuit by adding some more elements also try to keep the input ground separate from all other ground parts as much as possible.

Now just plug in the audio input jack to your phone

And that's how you build your very own LM386 audio amplifier from scratch. It's a simple yet powerful project to understand the basics of audio amplification.