LM386 Audio Amplifier.

The LM386 is a power amplifier designed for use in low voltage consumer applications. The gain is internally 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 inputs are ground referenced while the output automatically biases to one-half the supply voltage. The quiescent power drain is only 24 milliwatts when operating from a 6 volt supply, making the LM386 ideal for battery operation.

A nice feature of the LM386 is that it can drive a small speaker. This allows for an easy design and test of the amplifier in isolation, using a portable music player and a desktop speaker. Once the amplifier works fine, adding a microphone to complete the sound sensor should be easy.