What is the difference between NPN and PNP transistors?

NPN and PNP transistors differ in the direction of current flow and the type of doping used.

NPN and PNP transistors are both bipolar junction transistors (BJTs) and are used to amplify and switch electronic signals. The main difference between the two is the direction of current flow. In an NPN transistor, current flows from the collector to the emitter, while in a PNP transistor, current flows from the emitter to the collector. This means that the majority carriers in an NPN transistor are electrons, while in a PNP transistor, they are holes.

Another difference between NPN and PNP transistors is the type of doping used. NPN transistors are made up of a p-type base sandwiched between two n-type regions (collector and emitter), while PNP transistors have an n-type base sandwiched between two p-type regions. The doping of the base region determines the conductivity of the transistor and its ability to amplify or switch signals.

In summary, NPN and PNP transistors differ in the direction of current flow and the type of doping used. Understanding these differences is important for designing and analyzing electronic circuits that use BJTs.