What is the use of UJT relaxation oscillator?
William Taylor
Updated on March 19, 2026
What is the use of UJT relaxation oscillator?
Applications. Relaxation oscillator stays in rest position for some time and produces AC signals. These oscillators produce low-frequency signals. UJT Relaxation Oscillator is used in function generator to produce sweep signals, Electronic Beepers, SMPS, blinking lights, Voltage-controlled oscillators, inverters, etc..
Why it is called UJT?
Definition: Unijunction Transistor is a semiconductor switching device having 2 layers and 3 terminals and is abbreviated as UJT. It is called so because of the presence of only one junction. It has the ability to limit large power with a small input signal and is also known as a double base diode.
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.
What is UJT and its working?
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.
What is intrinsic stand ratio?
For a Unijunction transistor, the resistive ratio of RB1 to RBB shown above is called the intrinsic stand-off ratio and is given the Greek symbol: η (et1). Typical standard values of η range from 0.5 to 0.8 for most common UJT’s.
What is the voltage limit of capacitor in relaxation oscillator?
So, the capacitor will charge and discharge up to 6V. In this condition, V+ is greater than V-. So, output voltage Vout=+12V.
What is the symbol of UJT?
A unijunction transistor (UJT) is a three-lead electronic semiconductor device with only one junction that acts exclusively as an electrically controlled switch….Unijunction transistor.
| Type | active |
| Invented | General Electric (1953) |
| Pin configuration | B2, B1, emitter |
| Electronic symbol | |
|---|---|
| UJT N and P symbol |
What is meant by relaxation oscillator?
In electronics a relaxation oscillator is a nonlinear electronic oscillator circuit that produces a nonsinusoidal repetitive output signal, such as a triangle wave or square wave. The period of a relaxation oscillator is mainly determined by the relaxation time constant.
What is peak voltage in UJT?
Electronics Technology Fundamentals: Electron Flow Version with Lab Manual (3rd Edition) Edit edition. This problem has been solved: Problem 2SR from Chapter 26.4…
What is the principle of UJT oscillator?
The capacitor usually starts charging and continues to charge until the maximum voltage VBB. But in this circuit, when the voltage across capacitor reaches a value, which enables the UJT to turn ON (the peak voltage) then the capacitor stops to charge and starts discharging through UJT.
What is intrinsic standoff?
Intrinsic standoff ratio (η) : It is the ratio of RB1 to the sum of RB1 and RB2. It can be expressed as η = RB1/(RB1+RB2) or η = RB1/RBBO. The typical range of intrinsic standoff ratio is from 0.4 to 0.8.
Which device is used in the relaxation?
Resistor-capacitor (RC) relaxation oscillators are generally produced using operational voltage amplifiers or integrated circuits equipped with timers. When power is applied, the amplifier causes a capacitor to begin charging toward the voltage threshold under a preset time constant.
