What are the applications of UJT?

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 the characteristics of UJT?

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.
• Low cost.

Is UJT a thyristor?

The Unijunction Transistor or UJT for short, is another solid state three terminal device that can be used in gate pulse, timing circuits and trigger generator applications to switch and control either thyristors and triac’s for AC power control type applications.

How does a unijunction transistor work?

The Unijunction Transistor (UJT) will act as voltage breakdown device, when the input applied between emitter and base 1 reduces below breakdown value i.e., RB1 increases to a higher value. This shows that RB1 depends on the emitter current and it is variable.

Why UJT is called unijunction transistor?

The UJT consists of an n-type silicon semiconductor bar with an electrical on each end. Since the device has three terminals and one pn-junction, for this region this is called as a Unijunction Transistor (UJT). The device has only pn-junction so it forms a diode.

Why UJT is called Unijunction?

A Unijunction Transistor (UJT) is a three terminal semiconductor switching device. Since there is only one rectifying junction within the device, it is called a ‘Unijunction’ transistor.

How many terminal are there in 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 a uni junction transistor (UJT)?

A Uni Junction Transistor (UJT) is a device that is formed with a single junction of p-type and the n-type of the semiconductor material. It resembles to that of the diode with a single junction of the P-N. It looks almost like that of the Junction Field Effect Transistor (JFET). But the operation is completely different in comparison with it.

How does a 2n2646 unijunction transistor work?

The type 2N2646 unijunction transistor works nicely inside this indicated set up. There are basically two output signals: a negative-going pulse at UJT base 2, and a positive-going pulse at base 1.

What is a put (programmable unijunction transistor)?

A PUT (programmable unijunction transistor) is a 3-terminal 4-layer thyristor acting like a unijunction transistor. An external resistor network “programs” η. The intrinsic standoff ratio is η=R1/ (R1+R2) for a PUT; substitute R B1 and R B2, respectively, for a unijunction transistor. The trigger voltage is determined by η.

What is unijunction transistor relaxation oscillator and waveforms?

Unijunction transistor relaxation oscillator and waveforms. Oscillator drives SCR. During the capacitor discharge through the E-B1 saturation resistance, a pulse may be seen on the external B1 and B2 load resistors, Figure above. The load resistor at B1 needs to be low to not affect the discharge time.