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 is from an American publication from 1974. It, at the same time, limits the intensity of...
This two-relay circuit gives drive logic that is clear when analyzing the circuit. In the original...
12 V battery chargers provide higher unregulated voltage. With the regulator shown, obtained from...