This circuit, for vehicles with a 6 V battery, was found in the 1964 RCA transistors manual. Transistor 2N3054 can be replaced by a TIP41.
This circuit with 1W of output was found in a Mullard manual from 1960. The consumption is low and...
This circuit was found in an old documentation. It converts DC voltages and its maximum current...
In the figure we have the way to implement a 5 to 45 V zener diode with 50 mA of maximum current...