The LM386 is a power amplifier designed for use in low voltage consumer applications such as AM-FM radio amplifiers, Portable tape player amplifiers, Intercoms, TV sound systems, Line drivers, Ultrasonic drivers, Small servo drivers, and Power converters. It 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 quiescent power drain is only 24 milliwatts when operating from a 6 volt supply, making the LM386 ideal for battery operation.
When using the LM386 with higher gains ( bypassing the 1.35 kW resistor between pins 1 and 8 ) it is necessary to bypass the unused input, preventing degradation of gain and possible instabilities. This is done with a 0.1 microF capacitor or a short to ground depending on the dc source resistance on the driven input.
You can find example of the application of LM386 in audio power amplifier by following this link (source: FreeCircuitDiagram.com). Here is the quotation:
“The output power of this amplifier is between 250 mW and 1000 mW, depending on the type used. For LM386N-1, LM386M-1, LM386MM, the suitable supply voltage is 6V, with loudspeaker impedance 8? can give total harmonics distortion about 10% at power output 250-325 mW. For LM386N-3, the power source voltage is 9V with speaker impedance 8? can give total 10% harmonic distortion at 500-700 mW output power. For LM386N-4, power supply voltage is 16V and with speaker impedance 32? gives 10% total harmonic distortion at 700-1000 mW output power.”
- National Semiconductor – LM386 Low Voltage Audio Power Amplifier