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 ...
What is a Programmable Unijunction Transistor (PUT)? Simple – it is a three-lead electronic semiconductor device, similar to a unijunction transistor (UJT), except that its behaviour can be controlled ...