The LM386 is an 8 pin, Class AB amplifier. its mostly used at small low voltage projects and is quite popular among hobbyists like myself.
Lm386 circuit I used in the NES Portable V2
This amplifier works by taking a single channel audio signal and boosting it with a gain of about 20 (without a capacitor) to about 100. These can be used in several hobbyist projects like speakers, buzzers, boom boxes, and talking toys. Finding circuits like these are relatively cheap but it’s always fun to make your own as to learn how it works and mess around with the gain values.
How it Works:
The LM386 works by taking the input signal from pin 2 and 3 an audio tapped potentiometer can be put between the input and these pins to allow volume control. The gain is controlled by a resistor and capacitor between pins 1 and 8 or if you don’t need a very loud sound, not connecting the pins allows for a gain of just 20. From experience any old electrolytic capacitor will work but I would recommend a polystyrene capacitor, as they don’t cause as much noise, and are usually used in audio amplifiers. Pin 7 is the bypass. Putting a ceramic capacitor between this and the ground will reduce any noise coming from the input. Pin 5 is the output of the amplifier which can be connected to any speaker. Finally pins 4 and 6 are ground and +Vin respectively. Following the schematic below, you can easily make your own amplifier.