Electronics Engineering Articles



Unijunction Transistor (UJT) With Operation & Applications

What Is Unijunction Transistor (UJT)? The unijunction transistor, abbreviated UJT, is a three-terminal, single-junction device. The basic UJT and its variations are essentially latching switches whose operation is similar to the four-layer diode, the most significant difference being that the UJT’s switching voltage can be easily varied by the circuit designer. Like the four-layer diode, the UJT is always operated as a switch and finds most frequent applications in oscillators, timing circuits, and SCR/TRIAC trigger circuits. Unijunction Transistor (UJT) Operation A typical UJT structure, pictured in the figure, consists of…