Editing Unijunction transistor (section)

{{Short description|Type of transistor}}
{{Infobox electronic component
|name              = Unijunction Transistor
|image             = Image:unijunction transistors.jpg
|image_size        = 110px
|caption           = Unijunction transistors
|type              = [[Active device|active]]
|working_principle =
|invented          = [[General Electric]] (1953)
|first_produced    =
|symbol            = [[File:IEEE 315-1975 (1993) 8.6.8.svg|100px]] [[File:IEEE 315-1975 (1993) 8.6.9.svg|100px]]<br />UJT N and P symbol<ref>https://saliterman.umn.edu/sites/saliterman.dl.umn.edu/files/general/solid_state_power_switching.pdf Page 12</ref>
|pins              =  B2, B1, emitter
}}
A '''unijunction transistor''' ('''UJT''') is a three-lead [[Electronics|electronic]] [[semiconductor]] device with only one [[p-n junction|junction]]. It acts exclusively as an [[Electronic switch|electrically controlled switch]].

The UJT is not used as a linear amplifier. It is used in [[Electronic oscillator|free-running oscillator]]<nowiki/>s, synchronized or triggered oscillators, and pulse generation circuits at low to moderate frequencies (hundreds of kilohertz). It is widely used in the triggering circuits for [[silicon controlled rectifier]]s. In the 1960s, the low cost per unit, combined with its unique characteristic, warranted its use in a wide variety of applications like oscillators, pulse generators, saw-tooth generators, triggering circuits, phase control, timing circuits, and voltage- or current-regulated supplies.<ref name=Cleary64>J. F. Cleary (ed.), ''General Electric Transistor Manual'', General Electric, 1964 Chapter 13 "Unijunction Transistor Circuits"</ref> The original unijunction transistor types are now considered obsolete, but a later multi-layer device, the [[programmable unijunction transistor]], is still widely available.