The presented circuit uses a PNP transistor, which can be the BC558. Observe the polarity of the supply. The circuit is suggested by Texas Instruments opto-electronic documentation.
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...