The LM386 Audio Amplifier Module is a mono audio amplifier based on the LM386 chip. On eBay, it goes by various names and descriptions such as “LM386 Audio Amplifier Module 200 Times 5V-12V Input 10K Adjustable Resistance”.

The LM386M chip is available in a SO package (M) manufactured by Texas Instruments, and operates on a voltage range between 4 V and 12 V. It has an absolute maximum rating of 15 V. Package (M) has a dissipation rating of 0.73 W.

The LM386M version of the chip will provide a typical output of 325 mW, when the supply voltage is 6 V and the speaker load 8 Ω. A 9 V battery power supply will provide an output of around 500 mW.

The size of the PCB is 41 mm × 13 mm, manufactured using SMD components, and arrives ready assembled. This will save the user much time and resources.

As you can see, the PCB manufacturing is to a high quality standard, and the one I received worked straight away without any problems.

Projects

These modules are ideal for hobbyists because it can save much time and money if you were to buy and build it using discrete components.

A transistor based amplifier circuit would be far more expensive to make due to all the biasing resistors and inter-stage decoupling capacitors required. This neat little ready-made module provides a gain of 200.

If you have a stereo application, then you will need to buy two modules, however a single module is useful if you were experimenting with transistor radios.

It could be used with a Raspberry Pi, or even an Arduino project where amplification is required.

LM386 Chip

The LM386 is a wonderful chip by Texas Instruments. A power amplifier that requires minimal components to operate solves many cost issues associated with discrete component circuits. The application circuit is very simple and input / outputs are ground referenced.

Based on Class AB architecture, it is very simple to manufacture thus keeping the cost of the chip down. You can buy these chips on eBay at the going rate of ten for a pound, which is excellent for students, and schools operating on minimal budgets.

This chip has a quiescent current drain of 4 mA making it suitable for battery powered applications.

Screw Terminal

A convenient screw terminal allows the user to connect a suitable loudspeaker without any soldering.

Power LED

This amplifier module has a power LED that is very useful for troubleshooting. If this LED does not light, then make sure the power is reaching the circuit and it is correct.

200 Gain Audio Chip

This chip will also provide a signal gain of 200 when a 10-µF capacitor is connected between pin 1 and pin 8. This module already has this configuration; hence, it provides a gain of 200.

Bass Boost

This chip has frequency shaping capability, which is very useful if you have a speaker with a poor bass response. To enable this function, a series RC network between pin 5 and pin 1 is required. As you can see on the PCB, those components already appear to be connected.

Module PCB

Here is the underside of the PCB module. Both sides seem fine on the one I received.

Price

The price of this amplifier module can vary quite a lot depending upon the seller. On eBay you could expect to pay as little as one pound, including postage and it will arrive two weeks later from China. However many UK sellers have the same module selling for a fiver.

I bought mine from a seller based in China because I was in no hurry to receive it. The only one thing to look out for is to make sure they do not send you rejects. Sometimes you can get one where the components are not sitting properly on the board. The sockets might by sitting at an odd angle.

Overall, it is not a big deal as the boards tend to work, and if you politely let the seller know, then they are always very polite in return and provide satisfaction.

Specification

• Signal Gain 200 (multiplier)
• Operating voltage 5 V to 12 V DC
• On-board LED for power indicator
• Volume Control 10 k Ω preset
• Screw Terminal for speaker output connection
• Board size Approx. 41 mm × 13 mm