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Current between the two bases of the UJT sets up a voltage gradient in the semiconductor. When the voltage on the emitter of the UJT rises high enough to forward bias the emitter-base junction at the voltage of the interbase gradient where the emitter is located, the UJT "turns on".
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Characteristiccs of UJT?
The characteristics of a UJT are: stable triggering voltage, negative resistance, high pulse current capability and low value of triggering current.
What is a UJT?
UJT(UNIJUNCTION TRANSISTOR) is a three-lead electronic-semiconductor device with only one junction that exclusively as an eletrically controlled swtich andit is not used as a linear amplifier.
Draw the equivalent circuit of UJT?
we can draw an equivalent circuit for UJT USING a DIODE and two resistors.draw a diode in emitter lead ..draw the two resistors in series.As rb1 in base 1 lead ..and rb2 in base 2 lead ..draw rb1 as variable resistor.And put a voltage to the ujt in order to get a positive voltage in base two lead.
Describe the difference between a UJT and a PUT?
i. Constructional structures The UJT is made up of a lightly doped n-region known as the base region onto which is joined a small heavily doped p-region called the emmitter. The PUT on the other hand is a four layer device similar to an SCR except that the gate terminal of the PUT is connected to the n-region adjacent to the anode. ii.Operation The intrinsic stand-off ratio of a UJT is fixed hence operating characteristics can not be alterd. The PUT, on the other hand has operating characteristics that can be altered. These include base-base resistance,intrinsic stand-off voltage, valley current and peak current and all these can be altered by setting the values of two external resistors
What are the advantages and disadvantages of UJT?
The advantages of a UJT include low cost, a negative resistance characteristic, and a low value of triggering current. The main disadvantage is the inability to provide decent amplification.
Difference between bjt and ujt?
UJT is the voltage controlled device.in which only one mejority carriers are responsible for current flowing. UJT is one junction transistor and it is three terminal emitter and two base. BJT is the current controlled device. in which both mejority and minority carrier are responsiblefor current flowing. this type of transistor consists of two junction and three terminal these are : emitter , base , collector.
Why ujt called current controlled negative resistance device?
The On/OFF action in UJT is controlled by emitter current
Characteristiccs of UJT?
The characteristics of a UJT are: stable triggering voltage, negative resistance, high pulse current capability and low value of triggering current.
What is a UJT?
UJT(UNIJUNCTION TRANSISTOR) is a three-lead electronic-semiconductor device with only one junction that exclusively as an eletrically controlled swtich andit is not used as a linear amplifier.
Why name of the device is UJT?
UJT means Uni Junction transistor terminals are Emitter,Base1 and Base2.UJT is also called double base diode.UJT operates when the emitter is forward biased.voltage is applied between base1 and base2.If an external voltage is applied at terminal E,no current will flow in to the emitter as long as this applied voltage is less than emitter voltage.When this applied voltage exceeds emitter voltage,current will flow into the emitter and holes get injected from emitter to base1 and are repelled by base2.This results in increase in the region between the junction and the base 1.The increase in conductivity results drop in emitter voltage and increased forward bias of the junction.so emitter current also increases.Then it exhibits a negative resistance.
How does a ujt relaxation oscillator work?
The operation of the circuit is as follows: C1 charges through R1 until the voltage across it reaches the peak point. The emitter current then rises rapidly, discharging C1 through the base 1 region and R3. The sudden rise of current through R3 produces the voltage pulse. When the current falls to IV the UJT switches off and the cycle is repeated.
Can UJT replace BJT?
No. A unijunction transistor (UJT) is entirely different in design and application than a bipolar junction transistor (BJT). The UJT works on the principle of voltage modulation of the effective substrate resistance, while the BJT works on the principle of current amplification from one junction to the other, usually base-emitter to collector-emitter.
Why UJT's equivalent circuit has a diode?
A UJT is a special type of diode with a long resistive base having 2 contacts and acting as a voltage divider. The diode junction is created at a point on this base selected to set the trigger voltage of the UJT at which it will conduct. Therefore the equivalent circuit has a diode because the actual circuit has a diode.
How do you make ujt with npn and pnp transistors?
You dont. A UJT is a much simple device than either of those BJT's Maybe you want to make a multivibrator out of BJT's?
Draw the equivalent circuit of UJT?
we can draw an equivalent circuit for UJT USING a DIODE and two resistors.draw a diode in emitter lead ..draw the two resistors in series.As rb1 in base 1 lead ..and rb2 in base 2 lead ..draw rb1 as variable resistor.And put a voltage to the ujt in order to get a positive voltage in base two lead.
Describe the difference between a UJT and a PUT?
i. Constructional structures The UJT is made up of a lightly doped n-region known as the base region onto which is joined a small heavily doped p-region called the emmitter. The PUT on the other hand is a four layer device similar to an SCR except that the gate terminal of the PUT is connected to the n-region adjacent to the anode. ii.Operation The intrinsic stand-off ratio of a UJT is fixed hence operating characteristics can not be alterd. The PUT, on the other hand has operating characteristics that can be altered. These include base-base resistance,intrinsic stand-off voltage, valley current and peak current and all these can be altered by setting the values of two external resistors
What are the advantages and disadvantages of UJT?
The advantages of a UJT include low cost, a negative resistance characteristic, and a low value of triggering current. The main disadvantage is the inability to provide decent amplification.
