Editing Unijunction transistor (section)

==Applications==
Unijunction transistor circuits were popular in hobbyist electronics circuits in the 1960s and 1970s because they allowed simple [[oscillator]]s to be built using just one active device. For example, they were used for [[relaxation oscillator]]s in variable-rate strobe lights.<ref>
{{cite journal
 | journal = Popular Science
 | title = A Repeating Flash You Can Build
 | author = Ronald M. Benrey
 | volume = 185
 | issue = 4
 | pages = 132–136
 | date = October 1964
 | url = https://books.google.com/books?id=1yUDAAAAMBAJ&pg=PA132
 }}</ref>
Later, as [[integrated circuit]]s became more popular, oscillators such as the [[555 timer IC]] became more commonly used.

In addition to its use as the active device in relaxation oscillators, one of the most important applications of UJTs or PUTs is to trigger [[thyristor]]s ([[silicon controlled rectifier]]s (SCR), [[TRIAC]]s, etc.). A DC voltage can be used to control a UJT or PUT circuit such that the "on-period" increases with an increase in the DC control voltage. This application is important for large AC current control.

UJTs can also be used to measure magnetic flux. The [[Hall effect]] modulates the voltage at the PN junction. This affects the frequency of UJT relaxation oscillators.<ref>{{cite journal
|last1=Agrawal
|first1=S. L.
|last2=Saha
|first2=D. P.
|last3=Swami
|first3=R.
|last4=Singh
|first4=R. P.
|title=Digital magnetic fluxmeter using unijunction transistor probe
|journal=International Journal of Electronics
|date=23 April 1987
|volume=63
|issue=6
|pages=905–910
|doi=10.1080/00207218708939196
}}</ref> This only works with UJTs. PUTs do not exhibit this phenomenon.