Two transistors on a regenerative switch are used to trigger a triac. This circuit is from the RCA Power Circuits manual. Transistors admit equivalents.
This old circuit from a documentation from the 70s disconnects a TV from a signal obtained on the...
This traditional complementary symmetry circuit provides 20 W of rms power at a load of 8 ohms...
Using a CA3130 and a power transistor, this circuit can deliver a current of up to 500 mA with the...