Editing Common emitter (section)

{{short description|Type of electronic amplifier using a bipolar junction transistor}}
{{More footnotes|date=December 2008}}

[[File:NPN common emitter.svg|thumb|130px|Figure 1: Basic NPN common-emitter circuit (neglecting [[biasing]] details)]]

In [[electronics]], a '''common-emitter''' [[electronic amplifier|amplifier]] is one of three basic single-stage [[bipolar junction transistor|bipolar-junction-transistor]] (BJT) amplifier topologies, typically used as a [[Electronic amplifier#Ideal|voltage amplifier]]. It offers high [[current gain]] (typically 200), medium input [[Electrical resistance and conductance|resistance]] and a high output resistance. The output of a common emitter amplifier is inverted; i.e. for a [[sine wave]] input signal, the output signal is 180 degrees [[Phase (waves)|out of phase]] with respect to the input.<ref>{{Cite web|title=Common emitter configuration of BJT|url=https://www.electricalclassroom.com/common-emitter-configuration-of-bjt/|url-status=live|website=Electrical Classroom|archive-url=https://web.archive.org/web/20210605174333/https://www.electricalclassroom.com/common-emitter-configuration-of-bjt/ |archive-date=2021-06-05 }}</ref>

In this circuit, the base terminal of the transistor serves as the input, the collector is the output, and the emitter is ''common'' to both (for example, it may be tied to [[ground (electricity)|ground reference]] or a [[power supply rail]]), hence its name. The analogous [[field-effect transistor|FET]] circuit is the [[common-source]] amplifier, and the analogous [[vacuum tube|tube]] circuit is the [[common-cathode]] amplifier.