The NPN transistor is designed to pass electrons from the emitter to the collector (so conventional current flows from collector to emitter). The emitter "emits" electrons into the base, which controls the number of electrons the emitter emits. ... The transistor is kind of like an electron valve.
How does NPN and PNP transistor work?
NPN and PNP refer to the arrangement of the pieces that make up the transister. ... An NPN transistor has a piece of P-type silicon (the base) sandwiched between two pieces of N-type (the collector and emitter). In a PNP transistor, the type of the layers are reversed. Below is a typical cross section of a transistor.
How does a NPN transistor work as a switch?
NPN Transistor as a Switch
When a sufficient voltage (VIN > 0.7 V) is applied between the base and emitter, collector to emitter voltage is approximately equal to 0. Therefore, the transistor acts as a short circuit. ... Thus, when the transistor is switched ON, current will flow from source to ground through the load.
