LM386: Datasheet, Pinout, Audio amplifier, Application 2022

Author: Release time:2022-12-08 Source: Font: Big Middle Small View count:507

1. What is LM386 chip

 

The LM386 IC is an audio power amplifier IC designed for low-voltage consumer applications. The LM386 is available in an 8-pin dual in-line package (DIP-8). The voltage gain of the amplifier can be adjusted up to 20, which is increased to 200 by adding external components such as resistors and capacitors between pins 1 and 8.


The LM386 amplifier consists of 8 pins, of which pin 1 and pin 8 are gain control pins that allow volume control. Depending on the model, the amplifier can provide output power in the range of 0.25W to 1W using a 9 V supply.


Main performance parameters of LM386


  • Low noise and low distortion circuit

  • Small size (8-pin immersion package)

  • The quiet power of only 24mW at 6V supply

  • Standby current consumption of only 4mA

  • Operates from a wide supply voltage of 4V to 18V

  • Minimum to the maximum voltage gain of 20 to 200

  • Also manufactured in VSSOP and SOIC packages

  • Delivers sufficient power - approximately 700mW output common power at VS = 9V, RL = 8Ω, THD = 10%

  • Consumes low supply current - 4mA to 8mA with no input signal.

  • The voltage gain can be increased to 200 or 46dB by connecting a 10uF capacitor between pin 1(+) and pin 8(-).

  • The gain between 20 and 200 can be easily controlled by connecting the resistor in series with the capacitor.

  • Typical low harmonic distortion: 0.2%

  • Frequency response is from 40Hz to 100kHz rate.

  • Bandwidth: 300kHz total

 

 LM386 chip Datasheet >>


2. LM386 Pinout Diagram and Functions

 

lm386 pinout.jpg


Pin1 (Gain): Gain pin, used to adjust the amplifier gain by connecting the IC to an external component capacitor.


Pin 2 (Input -): In-phase input, used to provide audio signal.


Pin 3 (Input +): Inverted input, used to provide the audio signal.


Pin 4 (GND): Ground pin, connected to the system's ground.


Pin 5 (Vout): Output pin used to provide amplified output audio, connected to the speaker.


Pin 6 (Vs): Connected to the power supply, receiving positive DC voltage.


Pin 7 (Bypass): Bypass pin used to connect the decoupling capacitor.


Pin 8 (Gain): Gain setting pin, used to control the gain of the amplifier.

 

From this pin description, we can say that,

 

Pin 1 and Pin 8 represent the gain control terminals of the amplifier. These are the terminals where we can adjust the gain by placing a resistor and capacitor or just a capacitor between these terminals.


Pin 2 and Pin 3 represent the sound input signal terminals. These are the terminals where we place the sound we want to amplify, Pin 2 is the negative input and Pin 3 is the positive input.


Pin 4 is the GND (ground) terminal, which is connected to ground in the circuit.


Pin 5 represents the output of the amplifier. The amplified signal is output from this terminal.


Pin 6 receives a positive DC voltage so that the amplifier can receive the power needed to amplify the signal.


Pin 7 represents the bypass terminal. This terminal can be bypassed by a 15KΩ resistor. In circuit design, it is usually left open or grounded.

 

However, for better stability, a capacitor can be added to the circuit to prevent oscillation in the op-amp IC.

 

3. LM386 CAD model


1. LM386 circuit model

 

lm386 circuit model.jpg


2. LM386 size package drawing


 lm386 size package drawing.jpg


3. LM386 3D model drawing

 

lm386 3d model.png

 

4. LM386 Working Principle


1. LM386 internal circuit diagram

 

lm386 internal circuit diagram.png


2. How to use LM386?


The LM386 only needs a few capacitors and resistors to start working. A very basic and commonly used LM386 circuit is shown in the following diagram:


lm386 circuit.jpg

 

The IC is powered using pin 6 (usually 5 or 9V) and grounded on pin 4. The inverting pin (pin 2) is usually grounded and the non-inverting pin (pin 3) provides the audio signal.

 

This audio signal can come from a microphone or even from a 3.5 mm jack. 10k resistors are added in series with the audio signal and used as volume control. If you want full volume operation, you can ignore this potentiometer.

 

Pins 1 and 8 are used to set the gain of the amplifier. If there is nothing connected between these pins, the default gain will be 26 dB, but we can connect a 10 uF capacitor to both of them to get the maximum gain of the IC, which is 46 dB. Pin 7 is used to connect the filter capacitor (0.1 uf) of our amplifier IC to avoid unwanted oscillations.

 

The amplified audio signal can be obtained from pin 5 through a filter capacitor connected to an 8 ohm speaker. An RC network with 0.05uF and 10k resistors is optional.

 

5. LM386 Audio Amplifier Circuit Diagram Explained

 

The audio amplifier can be built using LM386 IC, 100 µF, 1000 µF, 0.05 µF, 10 µF, etc. capacitors, 10 KΩ potentiometer, 10 KΩ resistor, 12V power supply, 4Ω speaker, breadboard, and connection cable.

 

lm386 audio amplifier circuit diagram explained.jpg


This audio amplifier consists of 3 functional blocks such as power supply as well as output, bypass, and gain control. The design of this circuit design is very simple. First, the two power supply pins pin4 and pin6 are connected to GND and the corresponding voltage.

  

After that, connect the input from any type of audio source (e.g. cell phone or microphone). Here the circuit uses a cell phone as the audio source with a 3.5mm connector. The connector will have three connections, for example ground left and right audio.

 

The LM386 IC is a simple amplifier to which right or left audio is connected using an audio source with a ground terminal. The input level in this circuit can be controlled by connecting a potentiometer to the input. In addition, a capacitor will be connected in series with the input to remove the DC component. The gain of this IC will be adjusted to 20 and a capacitor (10 µF) will be connected between the two pins 1 and 8 of this IC and then the gain will be increased to 200.

 

Although the audio amplifier's datasheet suggests connecting a bypass capacitor at pin 7 as an option, we think that connecting a capacitor (100 µF) is helpful because it helps to reduce noise.

 

For the output connections, a capacitor (0.05 µF) and a resistor (10 Ω) will be connected in series between GND and pin 5 of the IC. This forms a Zobel network, and a filter containing the capacitor and resistor will be used to adjust the input impedance.

 

The speaker connection can be done with an impedance range of 4 Ω to 32 Ω, as the IC can drive any type of speaker in this range. The audio amplifier circuit uses a loudspeaker (4 Ω). The possibility of using a capacitor (1000 µF) to connect this speaker is very useful because it eliminates unwanted DC signals.

 

6. LM386 Amplifier Circuit (5 Types Included)

 

1. LM386 amplifier circuit --x20 amplifier

 

x20 amplifier.jpg


The smallest amplifier offers a gain of 20 with a minimum of parts. It is indeed an amplifier circuit, though with only one IC and one capacitor.


However, it has a very low output current (low drive power). Therefore, in practice, we may need more sound. We can increase it by the following simple way.

 

2. LM386 amplifier circuit - X200 size amplifier

 

X200 size amplifier.jpg



The gain of this circuit goes up to 200, because we connect the C2 capacitor to the IC through the positive terminal of C2 on pin 1 and the other positive terminal on pin 8. But sometimes too high gain is not good for us and we can control it with a resistor.

 

3. LM386 amplifier circuit - X50 low gain

 

X50 low gain.jpg



We added R2 resistor in series with C2 to lower the gain to 50.

 

4. LM386 amplifier circuit with bass boost

 

lm386 amplifier circuit with bass boost.jpg


Sometimes you may need more bass than usual. This circuit above can easily do that. By adding R2 resistor and C2 capacitor in series as in the circuit above.


The circuit has a bass booster and the output gain depends on the bass frequency. For example, the gain is 25dB: 100Hz and the gain is 19dB: 2kHz.


  • The volume is adjusted via VR1.

  • Both R1 and C3 will maintain good sound.

  • Improves the stability of high-frequency load.

 

5. LM386 amplifier circuit - 9V

The circuit below is also a 9V amplifier circuit, but with a gain of up to 200.

 

lm386 amplifier circuit - 9v.jpg



1. Parts list


1) 0.25W resistor, tolerance: 5%


R1:10Ω

R2: 1.2K

VR1:10K potentiometer

 

2) Capacitor


C1: 0.01μF 50V ceramic

C2:10μF 25V electrolytic

C3: 0.1μF 50V ceramic

C5: 220μF 16V electrolytic

 

3)Semiconductor and others


IC1: LM386, low-voltage audio amplifier

SP1: 8Ω 0.25W speaker

B1: Battery, 9V

 

2. Working principle

 

First, the signal enters input pin 3, a non-inverting input. This is a single-phase form of signal amplifier.


  • C1 absorbs the noise to protect the input.

  • C2 increases the gain of the amplifier.


More gain can be obtained by increasing the C2 capacitance. However, higher values result in higher distortion (should be less than 100μF).


The output comes from pin 5 of IC1.


The signal passes through the C4 coupling capacitor, which gives a better quality of the audio signal and blocks all DC voltage flow to the speaker.


Both R1 and C3 are connected in series, and they maintain the high frequency response better.

 

7. Application of LM386 Circuit

 

1. LM386 square wave oscillator

 

lm386 square wave oscillator.jpg


LM386 can also be used to create a square wave oscillator circuit, which makes it easier to create sound alarms using a speaker. Because this IC is an operational amplifier. Therefore, it is also a good choice when creating oscillator circuits.


According to the above circuit, the output frequency is about 1KHz, which can be changed by C2. The higher the capacitance the lower the frequency, and vice versa.

 

2. Other applications


The audio amplifier LM 386 IC can be used for various applications. It is one of the most important chips in the audio section and is commonly used in the following applications.


  • Battery-powered systems such as TV audio systems, ultrasonic drivers, recording sound from microphones

  • AM and FM radio amplifiers

  • Low-power audio amplifiers

  • Portable music players

  • Laptop/computer speakers and small portable stereos

  • Audio enhancers

  • Wien bridge oscillators

  • Walkie Talkies

  • Power converters

 

 

 


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