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Audio Power Amplifiers with LM386The LM386 is a versatile, small power amplifier designed for use in low voltageconsumer applications. The gain is internally set to 20 to keep external part count

low, but with the addition of an external resistor and capacitor between pins 1-8 the

gain can be set to any value from 20 to 200.

The inputs are ground referenced and the output automatically biases to one-half the supplyvoltage. The quiescent power drain is only 24 milliwatts when operating from a 6 Volt supply,

making the LM386 ideal for battery operation.

To make the LM 386 a more versatile amplifier, 2 pins (pin 1

and 8) are provided for gain control. With pins 1 and 8 open theinternal 1.35k resistor sets the gain at 20 (26 dB). If a capacitor

is placed between pin 1-8, bypassing the built-in 1.35k resistor,

the gain will go up to 200.

If a resistor is placed in series with the capacitor, the gain canbe set to any value from 20 to 200. Gain control can also bedone by capacitively coupling a resistor or FET transistor from

pin 1 to the ground.

Simple audio amplifier schematics with LM386

Operating Supply Voltage (VS) = 4v - 12v

The output power (POUT)

for LM386N-1, LM386M-1 at VS = 6V, RL = 8ohms, THD = 10% is 250-325 mW

for LM386N-3 at VS = 9V, RL = 8ohms, THD = 10% is 500-700 mW

for LM386N-4 at VS = 16V, RL = 32ohms, THD = 10% is 700-1000 mW.

Fig 1: LM386 Audio Amplifier with Gain = 20 and minimum part count

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86 Schematic diagrams http://www.hobby-hour.com/electronics/lm386-power-

02/12/2012

8/2/2019 LM386 Schematic Diagrams

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Fig 1: LM386 Audio Amplifier with Gain = 200

Fig 1: Audio Amplifier with bass boost

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86 Schematic diagrams http://www.hobby-hour.com/electronics/lm386-power-

02/12/2012