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Department of Electronics and Communication Engineering
ED and C 111
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Question 1 : As compared to UJT, SUS
Option-1 :triggers only in one direction
Option-2 :does not have a negative resistance characteristics
Option-3 :needs definite polarity of the applied voltage
Option-4 :triggers only at one particular voltage
Question 2 : Which of the following device does not have negative resistance characteristics
Option-1 :UJT
Option-2 :tunnel diode
Option-3 :SCR
Option-4 :FET
Question 3 : Which of the following statement is true for firing a triac
Option-1 :either T1 or T2 is negative and this is current pulses into the gate
Option-2 :T1 is negative and there is current pulse out of gate
Option-3 :T2 is negative and there is a current pulse out of the gate
Option-4 :eitherT1 or T2 is positive and there is a current pulse out of the gate
Question 4 : Thyristor A has rated gate current of 2A. thyristor B ,a rated gate curren t of 100mA
Option-1 :thyristor A is a GTO and B is a conventional SCR
Option-2 :thyritor B is a GTO and A is a conventional SCR
Option-3 :thyristor B may operate as atransistor
Option-4 :none
Question 5 : The function of connecting a zener diode in a UJTcircuit, used for the triggering of SCR is to
Option-1 :expedite the generation of trigger pulses
Option-2 :delay the generation of triggering pulses
Option-3 :provided a constant voltage to UJT to prevent erractic firing
Option-4 :provided a variable voltage to UJT as the source voltage changes
Question 6 : SCR can be turned on by
Option-1 :applying anode voltage to a sufficiently fast rate
Option-2 :applying sufficiently large anode voltage
Option-3 :increasing the temperature of SCR to a sufficiently large value
Option-4 :all of these
Question 7 : For a UJT employed for the triggering of an SCR, stand- off ratio = 0.64 & dc voltage source Vbb is 20V. The UJT would triggered when the emitter voltage is
Option-1 :12.8V
Option-2 :13.1 V
Option-3 :10V
Option-4 :none
Question 8 : in a UJT , maximum value of charging resistance is associated with
Option-1 :peak point
Option-2 :valley point
Option-3 :any point between peak and valley point
Option-4 :none
Question 9 : When a UJT is used for triggering of an SCR,the wave shape of the voltage obtained from UJT circuit is a
Option-1 :sine wave
Option-2 :saw tooth wave
Option-3 :trapezoidal wave
Option-4 :square wave
Question 10 : The phase- Locked Loops which have been optimised to provide a highly linear frequency to voltage transfer characteristics are
Option-1 :560,562 and 565
Option-2 :561,566 and 567
Option-3 :565 only
Option-4 :564 and 567
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