UJT stands for unijunction transistor, while in BJT stands for bipolar junction transistor. UJT is also known as "Double Base Diode" as it contains two bases; where as BJT contains three terminals namely, Emitter, Base and Collector. Difference between UJT AND BJT. A Uni Junction Transistor (UJT) is a device that is formed with a single. Electronics Tutorial about the Unijunction Transistor or UJT and how Unijunction Transistors can be used as a trigger generator for thyristors and triacs. Ujt is a uni junction transistor where, like bjt, a transistor with two junctions.