This tiny mono amplifier breakout board by Adafruit is surprisingly powerful for its size. It is based on the PAM8302 chipset and is able to deliver up to 2.5 Watts into 4 – 8 Ohm impedance speakers. Inside the chip is a miniature class D controller that is able to run on 2 – 5.5VDC. Since it is a class D, it is extremely efficient; when using an 8 Ohm speaker at half a Watt it will exceed 90% efficiency – making it an ideal choice for battery powered applications. The chipset also has built in thermal and over-current protection – an excellent upgrade over the LM386 amplifiers.

The A+ and A- inputs of the amplifier are run through 1.0uF capacitors, so they are fully differential. If you don’t have differential outputs, just tie the Audio- pin to ground. The output is “Bridge Tied” – that means the output pins connect directly to the speaker pins, no connection to ground. The output is a high frequency 250KHz square wave PWM that is then ‘averaged out’ by the speaker coil – the high frequencies are not heard. All the above means that you can’t connect the output into another amplifier, it should drive the speakers directly.

The board ships fully assembled and tested with a chunk of 2.54 mm breadboard pitch header (for using in a solderless breadboard) or a 3.5mm screw terminal for attaching the speaker.