E.D.C Electronics-800mcq

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Which of the factors doesn’t change the diode current.
a) Temperature
b) External voltage applied to the diode
c) Boltzmann‘s constant
d) Resistance


Answer: d
Explanation: I = Io [e(v/nVt) -1], as shown in this equation the diode current is dependent on temperature , voltage applied on the diode , Boltzmann’s constant but diode current is not dependent on resistance as it is independent of resistance.


Rate of change of concentration per unit length in a semiconductor is called as.
a) Concentration change
b) Concentration mixture
c) Concentration gradient
d) Concentration variant


Answer: c
Explanation: In a semiconductor the holes as well as electrons which are the charge carriers is not equally concentrated on all regions of the semiconductor the change in their rate is referred as concentration gradient.



In a P-N junction the positive voltage at which the diode starts to conduct consequently is called.
a) Cut off voltage
b) Saturation voltage
c) Knee voltage
d) Breakdown voltage


Answer: c
Explanation: At a certain critical voltage, a large reverse current flows and the diode is said to be in breakdown region, at this region the diode will be forward biased and starts to conduct consequently


In P-N junction V-I characteristics during forward biased, at what region the current increase is very low.
a) Saturation
b) Depletion
c) Cut off
d) Breakdown


Answer: b
Explanation: In the V-I characteristics the change in the current with respect to voltage is very less in depletion region due to the large resistance in the circuit as the resistance deceases by a certain value the current increases exponentially with voltage.


Which of the following diodes do not exhibits a constant reverse saturation current with the change in reverse saturation voltage.
a) 1N909
b) 1N405
c) 1N207
d) 1N676


Answer: c
Explanation: 1N207 is the germanium diode for which the reverse saturation current is not constant which the change in voltage due to the leakage in the surface of the diode and due to the generation of new current carriers.


By what percentage the reverse saturation current increases with 10 C rise in the temperature.
a) 25%
b) 12.5%
c) 50%
d) 7%


Answer: d
Explanation: As the temperature to the P-N junction diode increases the mobility of charges increases thus increasing the current, the reverse saturation current increases by 7% with 10C rise in temperature and doubles with every 100C rise in temperature.


What will be the decrease of barrier voltage with the rise in 10C in temperature?
a) 10V
b) 1mV
c) 10mV
d) 2mV


Answer: d
Explanation: As the temperature to the P-N junction diode increases the voltage across the junction decreases and the current increases with every degree rise in temperature the barrier voltage increases by 2mV.

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