In which configuration does an NPN transistor consist of a P-type material between two N-type materials?

The NPN configuration of a transistor is characterized by having two N-type semiconductor materials with a P-type material sandwiched in between. In this arrangement, the majority charge carriers in the N-type materials are electrons, while the majority charge carriers in the P-type material are holes. The flow of current in an NPN transistor involves electrons moving from the N-type emitter, through the P-type base, and into the N-type collector, which is essential for the transistor’s operation as an amplifier or a switch.

This structure allows for effective control of current flow, enabling it to amplify signals. The unique arrangement of materials and the type of doping define the transistor's mode of operation and its classification as an NPN transistor. Understanding this configuration is fundamental for working with transistors in various electronic applications.