This circuit has tone control, and its power depends on the supply voltage. The circuit is from the Philips integrated circuits manual from 1990.
This is one of the many versions of amplifiers with LM386. This was achieved in an old publication (1981). The...
This circuit uses unijunction transistors and drives a small speaker through an output...
This circuit can also be used as a shield if the excitation is made with 5 V and the output stage...