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 “backwa… ...

A 10K base resistor is used to bias an AC128 with a flashlight bulb as its collector load, and with a flying lead to the negative supply (remember this is a PNP transistor!) the bulb can be turned ...

The +ve lines in a PNP transistor become a common point for input and output that cannot be dropped. NPN transistor, the -ve lines create a single topic for both input and output, grounded.

There are numerous differences between NPN and PNP transistors, and even though both are bipolar junction transistors, the direction of current flow is the name of the game.

Immediately, I learned that the common base configuration gain was 6db lower than the common emitter. This blew my mind. Then I started checking input resistance and was shocked at how low it measured ...

One nice feature of the process is that the CMOS contacts and base junctions are common, enabling the addition of 0.5-mm digital CMOS digital transistors into high-performance analog subsystems.