Editing TRIAC (section)

{{Short description|Solid-state semiconductor device}}
{{other uses|Triac (disambiguation){{!}}Triac}}
{{ infobox electronic component
| name              = TRIAC
| image             = Kyocera FS-C5200DN - Murata MPS7511 power supply board - Renesas BCR12PM-14L-5156.jpg
| image_size        =
| caption           = A small plastic-cased TRIAC device mounted on a printed circuit board
| type              = [[Electronic component#Active components|Active]]
| working_principle = 
| invented          = 
| first_produced    = 
| symbol            = [[File:IEEE 315-1975 (1993) 8.6.15.svg|90px]]
| pins              = Terminal1, [[gate]] and Terminal2
}}

A '''TRIAC''' ('''triode for alternating current'''; also '''bidirectional triode thyristor''' or '''bilateral triode thyristor'''<ref>{{Cite web|last=Bhimsen|date=2020-10-06|title=Thyristor or Silicon Controlled Rectifier (SCR)|url=https://electronics-fun.com/thyristor-or-silicon-controlled-rectifier/|access-date=2021-10-31|website=electronics fun|language=en-US}}</ref>) is a three-terminal [[electronic component]] that conducts [[electric current|current]] in either direction when triggered. The term TRIAC is a [[genericized trademark]].

TRIACs are a subset of [[thyristor]]s (analogous to a [[relay]] in that a small voltage and current can control a much larger voltage and current) and are related to [[silicon controlled rectifier]]s (SCRs). TRIACs differ from SCRs in that they allow current flow in both directions, whereas an SCR can only conduct current in a single direction. Most TRIACs can be triggered by applying either a positive or negative voltage to the gate (an SCR requires a positive voltage). Once triggered, SCRs and TRIACs continue to conduct, even if the gate current ceases, until the main current drops below a certain level called the [[silicon controlled rectifier#Modes of operation|holding current]].

[[Gate turn-off thyristor]]s (GTOs) are similar to TRIACs but provide more control by turning off when the gate signal ceases.

The bidirectionality of TRIACs makes them convenient switches for [[alternating-current]] (AC). In addition, applying a trigger at a controlled phase angle of the AC in the main circuit allows control of the average current flowing into a load ([[phase control]]). This is commonly used for controlling the speed of a [[universal motor]], dimming lamps, and controlling electric heaters. TRIACs are [[Bipolar junction transistor|bipolar]] devices.