Editing Bipolar junction transistor (section)

== Current direction conventions ==
By convention, the direction of current on diagrams is shown as the direction that a positive charge would move.  This is called ''conventional current''.  However, in actuality, current in [[metal]] conductors is {{Efn|Some metals, such as [[Aluminium|aluminum]] have significant hole bands.<ref>{{cite book |last1=Ashcroft |last2=Mermin |title=Solid State Physics |date=1976 |publisher=Holt, Rinehart, and Winston |isbn=978-0030839931 |pages=[https://archive.org/details/solidstatephysic00ashc/page/299 299–302] |edition=1st |url=https://archive.org/details/solidstatephysic00ashc/page/299 }}</ref>}} due to the flow of electrons. Because electrons carry a negative charge, they move in the direction opposite to conventional current. On the other hand, inside a bipolar transistor, currents can be composed of both positively charged holes and negatively charged electrons.  In this article, current arrows are shown in the conventional direction, but labels for the movement of holes and electrons show their actual direction inside the transistor.

=== Arrow direction ===
The arrow on the symbol for bipolar transistors indicates the p–n junction between base and emitter and points in the direction in which [[conventional current]] travels.