A previous Design Idea describes a circuit that uses an astable multivibrator to drive an LED (Reference 1). The circuit in Figure 1 uses a simpler alternative approach. The circuit uses a 2N3904 NPN ...

The occasion for this project was retrofitting an illuminated wall picture with LED backlighting. As soon as I applied LED power, the brightness blinded me — much brighter than the original T20 ...

In the early days, PNP bipolar transistors were common, but the bulk of circuits you see today use NPN transistors. As [Aaron Danner] points out, many people think PNP transistors are “backward” but ...

The transistor is probably the most important invention in electronic engineering and the basis for nearly all integrated circuits (ICs). The transistor is a three-terminal electronic device that can ...