LM386 Audio Amplifier Circuit
There are various audio amplifier circuits designed using LM386 IC. Noise and interference are the main problems with these audio amplifiers. but In this circuit, there is very little noise with operation with a battery supply. This audio amplifier is very easy to construct and if a proper connection is done with the right component value then you will get a clear output with a loud sound.
Introduction to LM386
The LM386 is an all – in – one Class AB Audio Amplifier IC that can be used in a variety of applications. LM386 IC has been in use for decades and is still being used as Amplifier in Computer speakers and small Portable Stereos.
Pin Diagram of LM386
LM386 is a low voltage power amplifier with an inactive power draw of 24mW, which makes it suitable for battery controlled applications. The most common package for LM386 is an 8 – pin DIP. The following image shows the pinout diagram of the IC LM386
- The inverting input (Pin 2) of LM386 ic is connected to the Ground.
- Pins 6 and 4 are the power supply pins. The maximum power supply to LM386 is 15V. We have used a 12V Power supply in this project.
- Pin 7 sets the path for decoupling and a capacitor must be connected between Pin 7 and Ground. Pin 5 is the output pin. Proper filtering must be done before connecting the output to a speaker as any DC signal might permanently damage the speaker.
- The design of LM386 Audio Amplifier Circuit is very simple. First, connect the power supply pins (Pins 6 and 4) to 12V and Ground respectively. Note that the maximum power supply for LM386 is 15V.
- Next, we need to connect the input. The input can be given from any audio source like a mobile phone or a microphone. We have given the audio input from a mobile phone using the 3.5mm connector.
- NOTE: Simple 3.5mm connector (without a microphone) will have three connections: Left Audio, Right Audio and Ground. But LM386 is a Mono Audio Amplifier, so we need to connect either the Left audio or the Right Audio from the source along with the ground. But you can use the stereo to mono converter circuit to combine both audio channels to one. This circuit produces a mono output from a stereo input.
- If you want to control the audio loudness level that means the volume control, you need to connect a 10 KΩ Potentiometer at the audio input, by connecting the potentiometer or POT you will adjust the audio loudness as required Additionally, a small capacitor at input should be connected in series with the for filtering purpose.
- Without any gain control circuit, The gain of this Audio Amplifier internally set to 20. A 10 µF Capacitor connected between the gain control pins i.e. pins 1 and 8. Now the gain is changed to about 200.
- According to the datasheet of LM386, the bypass capacitor at Pin 7 is optional, you can connect a capacitor of 10µ. This capacitor is more suitable and using the 10uf capacitor at pin 7 with the ground provides very good output.
- Now at the output, at pin 5 connect a 0.047uf or 0.05 µF Capacitor (Non- polarized ceramic) and a Resistor of 10Ω in series to ground.
- Speaker connection. LM386 can drive any speaker within the impedance range of 4 Ω to 32 Ω. You can use a 4 Ω Speaker. Connect a capacitor from the value of between 220uf to 1000uf of 25v between the speaker and pin 5, this capacitor filter the signal and allow the only AC to the speaker by preventing unnecessary DC signals.
Working of LM386 Audio Amplifier Circuit
- A simple but efficient Audio Amplifier is designed using LM386 Audio Amplifier IC. The working of the circuit is very straight forward as all the work is done by the LM386 IC itself.
- When the system is powered on and proper audio input is given at the input, the LM386 Amplifier the input signal by a factor of 200 and drives the output speaker..
· LM386 is one of the important IC in the audio department and is mostly used in portable speakers, portable music players, and laptop speakers.
· This LM385 amplifier ic can also be used in TV Sound Systems, Ultrasonic Drivers, recording voice from microphone, building small speakers that are battery operated, in FM Radio Devices, etc.
source – electronicshub.org