It has a negative resistance region in the characteristics and can be easily employed in relaxation oscillators. From figure it is noted that for emitter potentials to the left of peak point, emitter current ie never exceeds ieo. This device is used to activating device for the triac. Basic electronics download ebook pdf, epub, tuebl, mobi. To study vi characteristics of scr and measure latching and holding currents. Ujt characteristics experimental setup consisting of 010v variable dual. Junction field effect transistor jfet the single channel junction fieldeffect transistor jfet is probably the simplest transistor available. The device, because of one pn junction, is quite similar to a diode but it differs from an ordinary diode as it has three terminals. A very small amount of current flow emitter tobase base. When an electric field is applied, the electrons move in the direction opposite. Zener diode zd1 clamps the pulsating dc voltage at 12v for the relaxation oscillator. Conduction in metals metals are filled with electrons. To find the zener break down voltage in reverse biased condition. Bipolar transistors are a three lead device having an emitter, a collector, and a base lead.
Graph of ujt characteristic curve, emitterbase1 voltage as a function of. Vi characteristics of scr al ameen engineering college,kulappully s7 power electronics lab department of electrical and electronics experiment 3 ujt trigger circuit for scr aim. The triac is the three terminal semiconductor device and used for controlling the current. A unijunction transistor ujt is a threelead electronic semiconductor device with only one junction that acts exclusively as an electrically controlled switch the ujt is not used as a linear amplifier. Due to this characteristic, the unijunction transistor can be employed in a variety of applications e. A unijunction transistor abbreviated as ujt is a threeterminal semiconductor switching device. In spite of having transistor added to its name, a unijunction transistor ujt working and characteristic curve varies completely from other counterparts. The bridge rectifier, d1 to d4, provides a pulsating dc form the 18v ac voltage. This device has a unique characteristic that when it is triggered, the emitter current increases regeneratively until it is limited by emitter power supply. Ujt relaxation oscillator, circuit diagram, ujt theory and working.
The ujt has achieved great popularity due to the following reasons. Sl no name of experiment subgroup date cycle remarks 1 2 3 static characteristics of scr static characteristics of a mosfet. Sketch the vi characteristics of an ujt and describe some. The ujt relaxation oscillator is called so because the. The device has only one junction, so it is called the unijunction device. To observe and draw the vi characteristics and regulation characteristics of a zener diode. Ujt triggering circuit ujt triggering it includes ujt triggering, scr silicon controlled rectifier, load resistor. Pe43 ujt relaxation oscillator bhagwant university. Ujt characteristics the static emitter characteristic a curve showing the relation between emitter voltage ve and emitter current ie of a ujt at a given inter base voltage vbb is shown in figure. Power electronics lab manual vii sem ec pe lab sub code. Demonstrate the operation of a ujtscr time delay circuit. Calculate and measure the time period of a ujtscr time delay circuit.
Introduction to unijunction transistor construction and. Date name of the experiment signature remarks 1 gate pulse generation using r, rc and ujt 2 characteristics of scr 3 characteristics of triac 4 characteristics of mosfet and igbt 5 ac to dc half controlled converter 6 ac to dc fully controlled converter 7 step down and step up mosfet based choppers 8 igbt based single phase pwm inverter. Ujt relaxation oscillator is a type of rc resistorcapacitor oscillator where the active element is a ujt unijunction transistor. Ujt is an excellent switch with switching times in the order of nano seconds. This is helpful for students to have a study, how to generate the pulse using ujt with variable frequency to trigger the scr and to understand the operation of it. But the thyristors are able to conduct the device in one direction and the triac is bidirectional. The power electronics laboratory is built around a reconfigurable circuit board, termed the powerpole board, along with accessory daughterboards. Single phase step down cycloconverter with r and rl loads. The 2n2646 is the most commonly used version of ujt.
General electric transistor manual, general electric, 1964 chapter unijunction transistor. Lab experiment electrical engineering electronic engineering. Original unijunction transistor or ujt is a simple device in which a bar of ntype semiconductor material into which ptype material is diffused. Theory of transistors and other semiconductor devices 1. Lc commutation circuit oscillation chopper circuit 29 visvesvaraya technological university. Semiconductor diodes and applications pn junction diode, characteristics and parameters, diode approximations, dc load line, temperature dependence of pn characteristics, ac equivalent circuits, zener diodes, halfwave diode rectifier. To study the operation of ujt firing circuit for scr. Power electronics lab manual ssit 1 contents experiment no page. This condition leads to the formation of an inversion layer just below the gate, leading to a channel formation and a. Ujts are very popular in switching circuits and are never used. This updated edition is an introduction appropriate for both the student and hobbyist to the theory and practice of electronics. A unijunction transistor ujt is a threelead electronic semiconductor device with only one. A pspice simulation followed by an experiment with a unijunction transistor ujt has been carried out to investigate stochastic resonance sr in which the response of a nonlinear system to a.
Model name pe01 ujt characteristics pe02 mosfet characteristics. To study ujt trigger circuit for half wave and full wave control. Insulated gate bipolar transistor igbt electrical4u. Kct college of engineering and technology departmentee power electronics and drives 1 index sr. The two transistor back to back connection forms a parasitic thyristor as shown in the above figure nchannel igbt turns on when the collector is at a positive potential with respect to emitter and gate also at sufficient positive potential v get with respect to emitted. A unijunction transistor ujt is an electronic semiconductor device that has only one junction. The experimental characteristics of sensors of nonelectrical quantities temperature, magnetic field, light, and pressure based on a unijunction transistor ujt, which is a component of a. Lc commutation circuit oscillation chopper circuit 29 8. Experiment program outcomes attained program specific outcomes attained 1 pn junction diode characteristics. Name of the experiment date marks signature of the staf pn junction diode characteristics 2 zener diode characteristics 3 rectifiers without and with cfilter 4 bjt characteristics ce configuration 5 fet characteristics cs configuration 6 scr characteristics 7 ujt characteristics 8 transistor biasing 9 cro operation and its measurements. Resistors r1 and r2 are employed as a current limiting resistances as shown in figure.
Fet questions and answers pdf free download also objective type multiple choice interview 2 mark important interview questions lab viva manual book. Many of these, typically one or two per atom in the metal, are free to move about throughout the metal. A synchronized ujt triggered circuit using an ujt is shown in the figure. Pdf basic electronics download full pdf book download. Pdf coherence resonance in a unijunction transistor. Ujt relaxation oscillator, circuit diagram, ujt theory and. This will cause a small amount of water to flow through this passage fig. For the love of physics walter lewin may 16, 2011 duration. Triac circuit working principle, construction and its. The simplest of all ujt circuits is the relaxation oscillator producing nonsinusoidal waveforms.
It is used in freerunning oscillators, synchronized or triggered oscillators, and pulse generation circuits at low to moderate frequencies hundreds of kilohertz. R m marston diode, transistor and fet circuits manual is a handbook of circuits based on discrete semiconductor components such as diodes, transistors, and fets. Further increasing the control pressure will cause the piston to move even more, revealing the small passage from the control to the output. Ujts have unidirectional conductivity and negative impedance characteristics acting more like a variable voltage divider during breakdown. Experiments 1 to study principle of operation of scr, plot vi characteristics and study the effect of gate triggering on turning on of scr. Po1, po5, po 12 pso1, pso2 10 scr characteristics po1, po2, po11 pso1, pso2. Pe43 ujt relaxation oscillator operating manual ver. Ujt relaxation oscillator pe43 is a compact, ready to use experiment board. Unijunction transistor applications the most common application of a unijunction transistor is as a triggering device for scr and triac but other ujt applications include sawtoothed generators, simple oscillators, phase control, and timing circuits. The details of the powerpole board are discussed in later sections of this experiment. An rc combination circuit connected at the emitter terminal of the ujt determines the frequency of oscillations.
To obtain the drain and transfer vi characteristics of fet and to plot the characteristics. Take laser print no photocopies allowed in executive bond sheet for a given experiment. It leads the reader through introductory understanding of the science underlying. Bipolar transistors have the following characteristics. Power electronics laboratory user manual department of. The base is formed by lightly doped ntype bar of silicon. This first experiment will familiarize you with the laboratory equipment and powerpole circuit board. Full wave rectifier using filter lab experiment electronics lab tutorials duration. From the name of the triac, the word triode is for alternating current and it is effectively developed with the help of the scr or thyristor. The basic construction of diac consist of two terminals namely mt1 and mt2. The diode ac switch, or diac for short, is another solid state, threelayer, twojunction semiconductor device but unlike the transistor the diac has no base connection making it a two terminal device, labelled a 1 and a 2 diacs are an electronic component which offer no control or amplification but act much like a bidirectional switching diode as they can conduct current from either.