Matching a sensor interface with a programmable logic converter or controller hardware that can accept only one type of input—npn or pnp—can be difficult.

Manufacturing companies, particularly those that mass-produce electronic circuits, work pretty much around bipolar junction transistors, like PNP and NPN. However, choosing between these two BJTs ...

He explains it all in a recent video you can see below. He does explain why PNP transistors don’t perform as well as corresponding NPN transistors, but they are still necessary sometimes.