325mW small amplifier circuit based on LM386

This is a small 325mW LM386 based amplifier circuit with a voltage gain of 200 that can be used as a simple desktop amplifier, signal tracker or to amplify the output of a personal radio, MP3 player, MP4 player or iPod.

How this circuit works:

The gain of the LM386 can be controlled with a capacitor between pins 1 and 8. Using the 10u capacitor shown above, the voltage gain is 200. Omitting this capacitor gives the amplifier a gain of 20.

The IC operates from 4 to 12 volts DC, with 12 volts being the maximum recommendation. Power from the USB port may be able to power this desktop amplifier circuit. The amplifier has an internal input impedance of 50K, which is shunted with a 22k logarithmic potentiometer, so the input impedance in this circuit will be lower than around 15k. The input is DC-coupled, so care must be taken not to amplify any DC from the preceding circuits, or you may damage the speakers. A coupling capacitor can be placed in series with the 22k controller to prevent this from happening.