Question: describe the components of current in npn transistor

title: Bipolar junction transistor
text: NPN is one of the two types of bipolar transistors , consisting of a layer of P - doped semiconductor ( the `` base '' ) between two N - doped layers . A small current entering the base is amplified to produce a large collector and emitter current . That is , when there is a positive potential difference measured from the base of an NPN transistor to its emitter ( that is , when the base is high relative to the emitter ) , as well as a positive potential difference measured from the collector to the emitter , the transistor becomes active . In this `` on '' state , current flows from the collector to the emitter of the transistor . Most of the current is carried by electrons moving from emitter to collector as minority carriers in the P - type base region . To allow for greater current and faster operation , most bipolar transistors used today are NPN because electron mobility is higher than hole mobility . 

Answer: answer: NPN is one of the two types of bipolar transistors , consisting of a layer of P - doped semiconductor ( the `` base '' ) between two N - doped layers .
That is , when there is a positive potential difference measured from the base of an NPN transistor to its emitter ( that is , when the base is high relative to the emitter ) , as well as a positive potential difference measured from the collector to the emitter , the transistor becomes active .