One of the applications of 555 timers is a class D amplifier. In its most simplistic form it can be built with a single 555 and the 200mA current capability is enough to drive a small speaker, making it a good replacement for a low power amplifier. But I wanted more; I wanted to use it to build an amplifier that had enough power to allow listening to music in a small room. Adding a high power stage to a classical 555 class D amplifier was too easy, so I decided to build my own high power 555.
555 class D amplifier - [Link]