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UJTstands forUnijunction Transistor
Full Form of UJT
What is UJT?
Unijunction Transistor (UJT) is a three-terminal semiconductor device consisting of a single PN junction that exhibits negative resistance characteristics, making it highly useful in switching and oscillator applications. The three terminals are named emitter (E), base 1 (B1), and base 2 (B2), and the device is typically constructed from a bar of N-type silicon with a P-type emitter alloyed into its side. In Indian engineering colleges and polytechnic institutions, the UJT is covered extensively in electronics, instrumentation, and electrical engineering syllabi at the diploma, undergraduate, and postgraduate levels. Practically, it is widely used in triggering circuits for thyristors such as SCRs and TRIACs, relaxation oscillators, sawtooth wave generators, voltage monitoring circuits, phase control applications, and timer circuits. Electronics laboratories in IITs, NITs, and other technical universities across India routinely include UJT-based experiments to help students understand its firing characteristics and oscillator behaviour. The device holds strong exam relevance for students preparing for competitive examinations such as GATE, IES, SSC JE, and PSU recruitments, where questions on oscillator circuits and triggering mechanisms are regularly asked.
UJT का फुल फॉर्म
यूनिजंक्शन ट्रांजिस्टर
Example
In our B.Tech lab at NIT Trichy, we used a UJT relaxation oscillator circuit to generate a clean sawtooth waveform on the oscilloscope.
UJT — frequently asked questions
What is the full form of UJT?
UJT stands for Unijunction Transistor, a three-terminal semiconductor device with a single PN junction used in switching and oscillator circuits.
What is UJT used for?
UJT is commonly used in relaxation oscillators, sawtooth wave generators, SCR triggering circuits, phase control circuits, and timer applications across power electronics.
Is UJT asked in the GATE exam?
Yes, UJT is an important topic in the GATE Electronics and Electrical Engineering papers, with regular questions on its characteristics, intrinsic stand-off ratio, and oscillator behaviour.