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The Unijunction Transistor (UJT)

Please post a schematic for further help. You May Also Like: PUT timing circuits are said to be usable to 10kHz. The resistor must be large enough so that it will never supply the high valley current I P.

The relaxation oscillator in Figure below is an application of the unijunction oscillator. PUT relaxation oscillator with component values. A unijunction transistor is composed of a bar of N-type silicon having a P-type connection in the middle.

R E charges C E until the peak point. A PUT programmable unijunction transistor is a 3-terminal 4-layer thyristor acting like a unijunction transistor. Thread starter T-bro Start date Jul 24, Replacing a 4 pin leaded inductor with a 2 pin Started by gkmaia Yesterday at If a linear ramp is required instead of an exponential ramp, replace the charging resistor with a constant current source such as a FET based constant current diode.

After capacitor discharge, the operating point resets back to the slope up to the peak point.

2N4891 transistor?

Started by fastline Yesterday at 8: Electro Tech is datawheet online community with overmembers who enjoy talking about and building electronic circuits, projects and gadgets. Characteristic curve, internal construction, schematic symbol. Media New media New comments Search media.


We still need V Vthe valley voltage. As anode current inceases, voltage increases up to the peak point. The gate lead voltage sets, programs, the peak anode voltage V P.

The PUT shares the four-layer structure typical of thyristors shown in Figure below. Forums New posts Search forums. The variable resistor should have a minimum resistor in series with it to prevent a low pot setting from hanging at the valley point. It varies from 0.

Hero Banned Jul 25, Click here to register now. You must log in or datasheey to reply here. A more accurate expression for frequency is given in Figure above.

2N Datasheet, PDF – Alldatasheet

Though it serves a function similar to the unijunction transistor, the PUT is a three terminal thyristor. PUT equivalent of unijunction transistor. The characteristic curve for the programmable unijunction transistor 2n489 Figure above is similar to that of the unijunction transistor. Quote of the day. T-bro New Member Jul 24, The unijunction emitter terminal has no effect on the capacitor until this point is reached.

Once the capacitor datashet below the valley point V Vthe E-RB1 resistance reverts back to high resistance, and the capacitor is free to charge again.

2N transistor datasheet & applicatoin notes – Datasheet Archive

Datasheft below show the PUT relaxation oscillator with the final resistor values. The resistance of R B1the saturation resistance is lowest at the valley point. The external resistor at B2 is optional. See Figure below a. It may be replaced by a short circuit.


A current spike flows through the cathode during capacitor discharge, developing a voltage spike across the cathode resistors.

It is inexpensive and in production. PUT relaxation oscillator Problem: Boolean Basics Intended for vatasheet with little or no exposure to digital logic, as well as those wanting a refresher or to understand Boolean algebra at a If the charging datasgeet ever could supply that much current, datasheer resistor would supply the valley current after the capacitor was discharged and the operating point would never reset back to the high resistance condition to the left of the peak point.

A unijunction transistor consists of two bases B1, B2 attached to a resistive bar of silicon, and an emitter in the center. The connections at the ends datasheeh the bar are known as bases B1 and B2; the P-type mid-point is the emitter.

The charging resistor must be small enough to supply enough current to raise the anode to V P the peak point Figure previous while charging the capacitor. To participate you need to register. For a better experience, please enable JavaScript in your browser before proceeding.

Published under the terms and conditions of the Design Science License. Selected 2n PUT parameters, adapted from 2n datasheet.