LM386 Audio Amplifier

Description

The LM386 Audio Ampifier is a general purpose single-channel audio amplifier that can handle up to 700mW and is easy to use.

PACKAGE INCLUDES:

• LM386 Audio Amplifier

KEY FEATURES OF LM386 AUDIO AMPLIFIER:

• 20x fixed gain adjustable up to 200x
• 700mW power
• 5-12V operation
• Easy to use and inexpensive

The LM386 are handy for providing basic audio amplification in a project such as if you want to drive a speaker off a PWM pin on a uC and want more oomph than the uC can provide directly.  They are general purpose amplifiers, so they can also be used in other small power amplification applications such as for driving small servos or ultrasonic drivers.

These parts are LM386N-1 or equivalent parts.  They operate at 5V – 12V and provide up to 700mW of power.  The higher the operating voltage, the higher the maximum amount of power that it can provide.  The output can drive loads from 4 to 32 ohms.  The lower the resistance of the load, the more power it can provide, so a 4 ohm speaker will be about twice as loud as an 8 ohm speaker.

The gain is fixed at 20x when using a minimal parts count setup, but volume can be adjusted using a pot on the input.  If a greater gain is desired, a capacitor and resistor can be added between pins 1 & 8 to program the gain up to a max of 200x.

Minimal Parts Count LM386 Example Circuit

Below is a minimal parts setup to drive a speaker off a PWM pin from a microcontroller.  The output capacitor between the amplifier and speaker is needed to avoid overheating the LM386 or damaging the speaker.  Value is not critical, but should be in the range of a 220-470uF or so.  Since the max input signal on the LM386 is 0.4V, the 5V PWM input will be clipped.

More Full Feature LM386 Example Circuit

For a more functional setup that adds additional capability, checkout to the circuit below.  It adds the following:

• Potentiometer on input to provide volume control.
• Series 100K resistor drops the 5V PWM voltage down so it is within the LM386 input spec.  Not needed when working with small signal inputs.
• A series 10uF input capacitor removes any DC offset that may be on the input signal.
• A small 10 ohm resistor / .047uF cap pair are added to the output to provide stability at high frequencies by providing a load for the amplifier at higher frequencies than the speaker can handle.
• A small tantalum or electrolytic cap of 1uF-4.7uF is added to the pin 7  to provide some bypass filtering on the input circuit.  A more readily available 0.1uF cap will also work fine in many applications.
• A 1000uF or similar large electrolytic filter cap is added across power and ground to primarily avoid 60hz noise coupling into the amplifier that can create hum.
• You will often see a 10uF cap or cap/resistor pair connected between pins 1 & 8 to increase the gain of the amplifier.  In breadboard setups, this can sometimes create too much feedback and so I have left it out to minimize the chance of having issues.  If you are trying to boost a very low signal like a condensor mic output, you may want the extra gain.  A 10uF cap across these pins (positive lead goes to pin 1) with no series resistor will give the max gain of 200x.

When using a solderless breadboard, be sure to keep wires and leads short to minimize noise pickup.

If you are looking for a prebuilt or more capable audio amplifier solution, take a look at our LM386 Audio Amp Module or PAM8403 Stereo Module down below.

Notes: 

1. None

Technical Specifications