# 50 top MCQ | exams | semiconductor diodes and it’s applications| question and answers

Answers indicated green with hints if required.

Diodes and it’s applications.

1.A pure semiconductor is often referred to as

A) extrinsic semiconductor

B) intrinsic semiconductor

C) doped semiconductor

D) none of the above

2.In a p-type semiconductor, the majority current Carriers are

A) free electrons

B) valence electrons

C) holes

D) protons

3. A diode is a

A)nonlinear device

B)linear device

C)unidirectional device

D)both a and c

4.A p-type semiconductor is a semiconductor doped with

A) trivalent impurity

B)pentavalent impurity atoms

C)impurity atoms whose electron valence is + 4

D)none of the above

5.What is the DC output voltage of an unfiltered half wave rectifier whos peak output voltage is 9.8 volt

A) 6.23 volt

B) 19.6 volt

C) 9.8 volt

D) 3.1 volt

(Hint : Vdc =0.318 * Vo/p(pk))

6.In n-type semiconductor the minority current carriers are

A) free electrons

B) protons

C) valence electrons

D) the holes

7.To a first approximation a forward biased diode is treated like a

A) open switch with infinite resistance

B) closed switch with the voltage drop of zero volt

C) close switch in series with the battery voltage of 0.7 volt

D) lose switch in series with a small resistance and a battery

8.What is the frequency of the capacitor ripple voltage in a full wave rectifier circuit if the frequency of the transformer secondary voltage is 60 Hertz

A) 60 Hertz

B) 120 Hertz

C) 50 Hertz

D) be this is impossible to determine

(Hint : F(out)=2 F(in))

9.In a full wave rectifier the DC load current equals 1 ampere, how much DC current is carried by each diode

A) 1/2 A

B) 1 ampere

C)2 ampere

D)0 Ampere

10.An n-type semiconductor is a semiconductor that has been doped with

A) trivalent impurity atoms

B) pentavalent impurity atom

C) impurity atoms whose electrons valence is + 4

D) none

11. For a silicon diode the barrier potential Vb is approximately equal to

A) 0.3 volt

B) 0.7 volt

C) 6.8 volt

D) 2.0 volt

12. To forward biased diode

A) the cathode voltage must be positive with respect to the anode

B) the anode voltage must be positive with respect to its cathode

C) the anode voltage must be negative with respect to its cathode

D) none of the above

13. The sharing of valence electron in a silicon crystal is called

A) doping

B) coupling

C) covalent bonding

D) the avalanche effect

14. Reverse bias diode acts like

A) open switch

B) close switch

C) small resistance

D) none of the above

15. When used as a voltage regulator, zener diode is normally

A) not baised

B) forward biased

C) reverse biased

D) none of the above

16. For a germanium diode, the barrier potential is

A) 0.3 volt

B) 0.3 eV

C) 0.7 volt

D) 0.7 eV

17.In a loaded zener regulator , the series resistor has a current of 120 mA , if the load current is 45 mA .How much is the zener current ?

A) 75 mA

B) 45 mA

C) 165 mA

D) this is impossible to determine

(Hint : Iz =Is – I(load))

18. The approximate voltage drop across a forward biased LED is

A) 0.3 volt

B) 2.0 volt

C) 5.6 volt

D) 0.7 volt

19. The output from an unfiltered half wave or full wave rectifier is a

A) smooth DC voltage

C) pulsating DC voltage

D) AC voltage

20.A 12 volt zener diode has a 1 watt power rating , what is the maximum rated zener current ?

A) 1 ampere

B) 46.1 milliampere

C) 83.3 milliampere

D) 120 milliampere

(Hint: I=P/V)

21. If the arrow of the Crystal diode symbol is positive with respect to bar , then the diode is ….

A) forward

B) reverse

C) either forward or reverse

D) none of the above.

22.In the breakdown region ,a zener diode behaves like a …. source

A) constant voltage

B) constant current

C) constant resistance

D) none of the above

23. If the temperature of Crystal diode increases ,the leakage current…

A) remains the same

B) decreases

C) increases

D) become zero

24. When the crystal current diode is large , the bias is

A) forward

B) inverse

C) poor

D) reverse

25. for the same secondary voltage , output voltage from a centre tap rectifier is….. than that of bridge rectifier.

A) twice

B) thrice

C) one half

D) four times

26. Zener diode is used as

A) an amplifier

B) a voltage regulator

C) a multivibrator

D) a rectifier

27. The disadvantage of a half wave rectifier is that the

A) components are expensive

B) diodes must have a higher power rating

C) output is difficult to filter

D) none of the above

28. A zener diode has … breakdown voltage

A) undefined

B) zero

C) sharp

D) none of the above

29. Zener diode is always… connected

A) reverse

B) either reverse or forward

C) forward

D) none of the above

30. A 10 volt power supply would use as ……filter capacitor

A) electrolytic capacitor

B) mica capacitor

C) paper capacitor

D) air capacitor

31. The…. filter circuit results in the best voltage regulation

A) choke input

B) capacitor input

C) resistance input

D) none of the above

32. If the PIV rating of a diode is exceeded,…..

A) the diode conducts poorly

B) the diode is destroyed

C) the diode behaves like a zener diode

D) none of the above

33. Zener diode is destroyed if it…

A) is forward biased

B) is reverse biased

C) carries more than the rated current

D) none of the above

34. If the doping level of a crystal diode is increased ,the breakdown voltage

A) remains the same

B) is increased

C) is decreased

D) none of the above

35. Mains AC power is converted into DC power for

A) lightning purpose

B) heaters

C) using in electronics equipments

D) none of the above

36. The ripple factor of a half wave rectifier is…

A) 2

B) 1.21

C) 2.5

D) 0.48

37. The maximum efficiency of a half wave rectifier is…….

A) 40.6%

B) 81.2%

C) 50%

D) 25%

38. The most widely used rectifier is

A) half wave rectifier

B) centre-tap full wave rectifier

C) bridge full-wave rectifier

D) none of the above

39. Zener diode has…

A) 1 PN junction

B) 2 PN junction

C) 3 PN junction

D) 4 PN junction

40. Avalanche breakdown in a crystal diode occurs when

A) the potential barrier is reduced to zero

B) forward current exceeds a certain value

C) reverse bias exceeds a certain value

D) none of the above

41.When crystal diode is used as a rectifier, the most important consideration is….

A) forward characteristic

B) doping level

C) reverse characteristic

D) PIV rating

42. When the graph between current through and voltage across a device is a straight line , the device is referred to a

A) linear

B) active

C) nonlinear

D) passive

43. The leakage current in a crystal diode is due to

A) minority charge carriers

B) majority charge carriers

C) junction capacitance

D) none of the above

44. The PIV rating of a crystal diode is…. …..that of equivalent vacuum diode

A) same as

B) lower than

C) more than

D) none of the above

45. The knee voltage of a crystal diode is approximately equal to..

A) barrier potential

B) breakdown voltage

C) applied voltage

D) forward voltage

46.If the doping level in a crystal diode is increased , the width of depletion layer

A) remains the same

B) is increased

C) is decreased

D) none of the above

47. The doping level in a zener diode is …..that of a crystal diode

A) same as

B) more than

C) less than

D) none of the above

48. A series resistance is connected in the zener circuit to…

A) protect the zener diode

B) properly reverse bias the zener

C) properly forward bias the zener

D) none of the above

49. zener diode is a …. device

A) non-linear

B) linear

C) amplifying

D) none of the above

50. In a half wave rectifier ,the load current flows for

A) the complete cycle of input signal

B) only for positive half cycle of the input signal

C) less than half cycle of the input signal

D) more than half cycle but less than the complete cycle of input signal