How UJT is applied in the circuit?

The most common application of a unijunction transistor is as a triggering device for SCR’s and Triacs but other UJT applications include sawtoothed generators, simple oscillators, phase control, and timing circuits. The simplest of all UJT circuits is the Relaxation Oscillator producing non-sinusoidal waveforms.

What are UJT and its characteristics?

The special features of a UJT are : A stable triggering voltage (VP)— a fixed fraction of applied inter base voltage VBB. A very low value of triggering current. A high pulse current capability. A negative resistance characteristic.

What are the applications of UJT?

Applications of unijunction transistor (UJT)

The unijunction transistor (UJT) used as relaxation oscillator.
It is used as voltage detector.
The UJT is used for switching.
It is widely used as triggering device for silicon control rectifier (SCR) and TRIAC.
The UJT is used in phase control circuit.

Why do we use UJT?

The UJT is not used as a linear amplifier. It is used in free-running oscillators, synchronized or triggered oscillators, and pulse generation circuits at low to moderate frequencies (hundreds of kilohertz). It is widely used in the triggering circuits for silicon controlled rectifiers.

What are the terminals of a Unijunction Transistor?

The UJT has three terminals: an emitter (E) and two bases (B1 and B2) and so is sometimes known a “double-base diode”. The base is formed by a lightly doped n-type bar of silicon. Two ohmic contacts B1 and B2 are attached at its ends.

What is UJT and its symbol?

The symbol of UJT is designed in such a way that arrow is bent and shown that it is in the direction towards the channel. It resembles of JFET. If the channel is made of the N-type then the terminal called emitter is of P-type and vice-versa.

What are the advantages of a UJT?

Advantages of Unijunction Transistor (UJT) low cost. negative resistance characteristics. Requires low value of triggering current. A stable triggering voltage.

What is difference between UJT and BJT?

UJT stands for unijunction transistor, while in BJT stands for bipolar junction transistor. UJT is only one junction is present in BJT, while in BJT consist of two junctions. UJT is also known as double-base diode as contains two bases while in BJT contain three-terminal namely emitter, base, and collector.

How is the output of an UJT oscillator determined?

UJT Relaxation Oscillator consists of a UJT circuit with its emitter connected to a resistor and a capacitor. The timing of the output waveform is determined using the RC time constant. Supply voltage VBB is applied to the circuit. The capacitor starts charging through the resistor R1.

What does UJT stand for in electrical category?

UJT stands for Unijunction Transistor. UJT is a two-layered, three-terminal, solid-state switching device. Unlike a BJT, it has only one junction that’s why it is called Unijunction Transistor. UJT can act as an electrically operated solid state switch.

When does The unijunction transistor ( UJT ) fires?

For so long the the voltage VE across the capacitor stays lower than the Vp, the UJT terminals across B1, B2 exhibits an open circuit. But the moment the voltage across CT goes beyond Vp, the unijunction transistor fires, quickly discharging the capacitor, and initiating a fresh cycle.

How does RT and CT work in the UJT circuit?

Here the components RT and CT work like the timing elements and determine the frequency or the oscillation rate of the UJT circuit.

How UJT is applied in the circuit?