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 two types of standard transistors are PNP and NPN which differs in circuit symbols. The layers of semiconductor material used to make the transistor are denoted by the letters. To keep a straight ...

For circuit designs that use complementarybipolar transistors,you sometimes need to sort the NPNand PNP transistors to have matchingdc-current gains (β). One example of acircuit requiring matching is ...