Speaking of the Pinecil, it uses an unorthodox driving circuit – it has an NPN transistor, but its base driven through a capacitor, so that only the AC component of the driving signal gets through.

In this lesson, students build two circuits and explore how transistors ... The diagram illustrates the basic design of an NPN junction transistor. Two slices of N-type semiconductor, the emitter ...

Thus the three basic bipolar transistor circuit configurations have equivalents ... There are equivalent P-channel devices, just as there are PNP and NPN bipolar transistors.

What does "NPN" or "PNP" mean in terms of a transistor ... Typical signs of a failing transistor include a circuit that's not functioning as expected, or a device that's overheating or not powering on ...