Unijunction transistor (ujt)

The unijunction transistor (UJT) is a three-terminal semiconductor device that contains only one PN junction. It consists of a lightly doped N-type semiconductor bar with two terminals (B1 and B2) on either side and an emitter terminal. A PN junction is formed close to B2. The UJT exhibits negative resistance in its operating region between the peak and valley points on its IV characteristics curve, making it useful for oscillators and timing circuits. It can be used more efficiently than BJTs in switching applications.