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.
August 2017 - Heat sinks for use with Arcol / Aluminum resistors can be obtained from Mouser...
Can be used as a shield, this old American documentation circuit offers digitally selected...
This circuit charges a battery to power a flashlight at night. The circuit is from an English...