The LM386 Audio Power Amplifier is use in low voltage consumer applications. The gain is set to 20 to keep external part count low. But the addition of an external resistor and capacitor between pins 1 and 8 will increase the gain to any value from 20 to 200.
The LM386 is an integrated circuit containing a low voltage audio power amplifier. It is suitable for battery-powered devices such as radios, guitar amplifiers, and hobby electronics projects. The IC consists of an 8 pin dual in-line package (DIP-8) and can output 0.25 to 1 watts of power depending on the model using a 9-volt power supply.
- Battery operation
- Minimum external parts
- Wide supply voltage range: 4V-12V or 5V-18V
- Low quiescent current drain: 4mA
- Voltage gains from 20 to 200
LM386 audio amplifier can amplify sound from Microphone. This circuit can use as “Small mic and loudspeaker system” for a small space like a room. This circuit also use in many applications like portable music players, intercoms, radio amplifiers, TV sound systems, Ultrasonic drivers etc. It also uses as sound sensor for microcontrollers. It is inexpensive, low power operate and only need few components to work. This circuit is based on LM386 IC to amplify sound.
LM386 is a low voltage audio amplifier and frequently used in battery powered music devices like radios, guitars, toys etc. The gain range is 20 to 200, gain is internally set to 20 (without using external component) but can increase to 200 by using resistor and capacitor between PIN 1 and 8, or just with a capacitor. Voltage gain simply means that Voltage out is 200 times the Voltage IN. LM386 has a wide supply voltage range 4-12v. Below is the Pin diagram of LM386.
- IC LM386
- Condensor Mic
- Speaker 8ohm
- Capacitors- 220uF, 10uF (two), 0.1uF, 0.05uF
- Resistor- 10k (two)
- Potentiometer- 100k
- Battery 5-12v
PIN 1 and 8:
These are the gain control PINs, internally the gain is set to 20 but it can increase up to 200 by using a capacitor between PIN 1 and 8. We use 10uF capacitor C1 to get the highest gain i.e. 200. Gain can adjust to any value between 20 to 200 by using proper capacitor.
Pin 2 and 3:
These are the input PINs for sound signals. 2 is the negative input terminal, that connects to the ground. 3 is the positive input terminal, in which sound signal is amplify. In our circuit it is connect to the positive terminal of the condenser mic with a 100k potentiometer RV1. Potentiometer acts as volume control knob.
A capacitor C5 of 0.1uF is use along with potentiometer, to remove the DC component of input signal and only allow audio (AC component) to fed into LM386.
Pin 4 and 6:
These are the power supply Pins of IC, Pin 6 for is +Vcc and Pin 4 is Ground. The circuit can also power with voltage between 5-12v.
This is the output PIN, from which we get the amplified sound signal.
The output signal has both AC and DC component, and DC component is undesirable and can’t be fed to Speaker. So to remove this DC component, a capacitor C2 of 220uF has been used. This has the same function as Capacitor C5 (0.1uF) at input side.
Along with this capacitor, a filter circuit of Capacitor C3 (.05uF) and resistor R1 (10k) has been used at the output PIN 5. This filter also called the “Zobel network”, this electronic filter is use to remove the sudden High frequency oscillations or noise.
This is the bypass terminal. It can left open or maybe ground using a capacitor for stability.
1×LM386 Audio Power Amplifier