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Test answers for Semiconductor Electronics Test 2016

(56 / 16) Last updated: October 22
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56 Answered Test Questions:

1. An SCR is a solid state equivalent of a _____.

Answers:

• triode

• pentode

• thyratron

• diode

2. A P-type material is _____.

Answers:

• positively charged

• negatively charged

• electrically neutral

• none of the above

3. The stability factor of a biasing circuit is 10. What does it mean?

Answers:

• Ic changes 10 times as munch as any change in Ico(leakage current)

• Ib changes 10 times as much as any change in Ico

• Ie change 10 times as munch as any change in Ico

4. According to the Barkhausen criterion for oscillators_______.

A – open loop gain
β – feed back factor

Answers:

• Aβ < 1

• Aβ > 1

• Aβ = 1

• Aβ ≤ 1

5. If the reverse bias on the gate of an FET is increased , the width of the conducting channel will _____.

Answers:

• increase

• decrease

• remain constant

6. An FET has the following parameters IDSS = 32mA , VGS ( off ) = -8V , VGS = -4.5V. What will be the drain current?

Answers:

• 5.2 mA

• 6.12 mA

• 7.03 mA

• 7.45 mA

7. For good stabilization of the operating point in a voltage divider bias, the current I, flowing through potential dividers R1 and R2, should be equal to or greater than _____.
(IB-base current)

Answers:

• 2IB

• 10IB

• 4IB

• IB/2

8. If in a transistor IE = 10.5mA , IC = 10mA,the value of β will be _____.

Answers:

• 0.2

• 200

• 100

• 20

9. The slope of the D.C load line of a transistor circuit having a collector load Rc is _____.

Answers:

• Rc

• 1/Rc

• -1/Rc

• 2Rc

10. Tuning is generally accomplished by varying _____.

Answers:

• L(inductor)

• C(capacitor)

• both L and C

• R(resistor)

11. A triac can pass a portion of _____.

Answers:

• positive half-cycle through the load

• negative half-cycle through the load

• both positive and negative half-cycles through the load

• None of the above

12. An A.C supply of 230v is applied to a half wave rectifier circuit through a transformer of turn ratio 10:1. Its D.C voltage output will be _____.

Answers:

• 5v

• 12v

• 10.36v

• 5.18v

13. A vacuum tube conducts current _____.

Answers:

• from the cathode to the anode

• from the anode to the cathode

• in both the above directions

• alternately in both directions

14. If a circuit of full-wave centre-tapped rectifier with capacitor filter employs a load RL = 100Ω, and C = 1050µF and the frequency is 50HZ , what would be the ripple factor?

Answers:

• 40%

• 30%

• 22%

• 27%

15. Two identical germanium diodes are connected in series opposition. A 10V battery is impressed upon this series arrangement. What will be the voltage across each diode room temperature if the Zener breakdown voltage of each diode is 9.8V?

Answers:

• VD1= 0.2V , VD2 = 9.8V

• VD1 = 10V , VD2 = 0V

• VD1 = 0V , VD2 = 10V

• VD1 = 9.8V , VD2 = 0.2V

16. A varactor diode can function as a variable capacitor with a________ forward bias.

Answers:

• very slight

• moderate

• heavy

17. Radio frequencies have their range above _____.

Answers:

• 20KHZ

• 50KHZ

• 100KHZ

• 200KHZ

18. Tuned amplifiers are generally operated as

Answers:

• class A amplifiers

• class B amplifiers

• class AB amplifiers

• class C amplifiesrs

19. In the collector feedback biasing, β = 57 , RC = 1 kΩ , IB = 60µA and VCB = 4.5V. The value of the stability factor will be _____.

Answers:

• 30.4

• 32.9

• 57

• 4.5

20. In the enhancement mode (MOSFET) , conductivity increases _____.

Answers:

• with the decrease in positive gate voltage

• with the increase in positive gate voltage

• with the decrease in negative gate voltage

• with the increase in negative gate voltage

21. A three-stage amplifier has a first-stage voltage gain of 100, a second stage voltage gain of 200 and a third stage gain of 400. The total voltage gain in db will be _____.

Answers:

• 130 dB

• 140 dB

• 132 dB

• 138 dB

22. The output characteristics of an FET closely resemble the plate characteristics of a________ valve.

Answers:

• diode

• triode

• tetrode

• pentode

23. The Q-factor of a parallel tuned circuit is given by _____.

Answers:

• 1/R√C/L

• R√L/C

• 1/R√L/C

• R√C/L

24. At parallel resonance, a tuned circuit offers an impedance of _____.

Answers:

• C/LR

• R/LC

• L/CR

• 2L/CR

25. When a transistor has to act as a switch, it must operate in _____.

Answers:

• the active region

• the cut-off region

• the saturation region

• both the cut off and the saturation regions

26. The V-I characteristics of a triac in the first and third quadrants are essentially identical to those of _______ in the first quadrant

Answers:

• a transistor

• a UJT

• a zener diode

• an SCR

27. In the d.c. equivalent circuit of a transistor amplifier , the capacitors are regarded as _____.

Answers:

• Open

• Short

• Sometimes open and sometimes short

• Unchanged

28. The output frequency of a half-wave rectifier is _____.

Answers:

• double the input A.C frequency

• half the input A.C frequency

• equal to the input A.C frequency

• None of the above

29. The maximum efficiency of a full wave rectifier is _____.

Answers:

• 40%

• 81.2%

• 90%

• 99%

30. If the collector supply voltage is 10v, the collector cut off voltage under D.C conditions will be _____.

Answers:

• 5v

• 10v

• 20v

• 30v

31. The relationship among bandwidth, resonant frequency and Q of a tuned circuit is _____.

Answers:

• BW = Q/fr

• BW = Q fr

• BW = fr√Q

• BW = fr/Q

32. Why  is the control grid of a tube always held at negative potential W.R.T cathode.?

Answers:

• in order to avoid heating of the tube

• in order to obtain faithful amplification

• in order to set its operating point

• None of the above

33. If the input to an integrating circuit is a square wave, the output will be _____.

Answers:

• triangular

• rectangular

• saw-tooth

• spiked

34. If in a transistor , Ic = 9.5mA , Ie = 10mA , the value of α will be _____.

Answers:

• 0.95

• 10

• 9.5

• 0.095

35. What would be the gain of a negative feedback amplifier with an internal gain A=100 and a feedback factor m=0.9?

Answers:

• 1.09

• 12

• 5.5

• 7

36. In an R-C phase shift oscillator, an R-C network is designed to introduce a phase shift of _____ .

Answers:

• 300

• 600

• 900

• 1800

37. If the input to a differentiating circuit is a square wave, the output will be _____.

Answers:

• rectangular

• spiked

• triangular

• sinusoidal

38. For faithful amplification, VBE must not fall below _____.

Answers:

• 0.9v for si transistors

• 0.5v for si transistors

• 0.3v for si transistors

• 0.7v for si transistors

39. Tuned amplifiers are used for the amplification of _____.

Answers:

• audio frequencies

• RF

• very low frequencies

• very high frequencies

40. For an R-C phase shift oscillator , the frequency of oscillation will be given as _____.

Answers:

• fo = 1/2П√RC

• fo = 1/2П√6RC

• fo = 1/√2ПRC

• fo = 2/√2ПRC

41. A reversed biased P-N junction has a resistance of the order of _____.

Answers:

• Ω

• KΩ

• MΩ

• mΩ

42. The impedance of a parallel tuned circuit at resonance is _____.

Answers:

• 0

• low

• very high

• very low

43. A transistor amplifier has 4v,2mA as the operating point. For faithful amplification, the collector current due to signal alone should not exceed _____.

Answers:

• 2mA

• 1mA

• 4mA

• 8mA

44. A D.C milliammeter connected to a half-wave rectifier supplying a maximum current of 10mA will read _____.

Answers:

• 10 mA

• 20 mA

• 5 mA

• 3.18 mA

45. An SCR combines the features of_____.

Answers:

• a rectifier and an amplifier

• a rectifier and a transistor

• a rectifier and an oscillator

• a rectifier and an inverter

46. Hartley oscillator is _____.

Answers:

• an RC oscillator

• an LC oscillator

• a Crystal oscillator

47. If in a transistor VCB= 4V , VBE = 0.7V, the VCE will be equal to _____.

Answers:

• 4.7v

• 5.4v

• 3.3v

• 0.7v

48. Vacuum tubes are _____.

Answers:

• linear devices

• non-linear devices

• both linear and non-linear under different conditions

49. The input and output voltages of a CE transistor amplifier are _____.

Answers:

• in phase

• 90° out of phase

• 180° out of phase

• 120° out of phase

50. An FET has ________ temperature co-efficient of resistance.

Answers:

• 0

• positive

• negative

51. An :FET is a _____.

Answers:

• bipolar device

• tripolar device

• unipolar device

52. The complementary MOS(CMOS) uses _____.

Answers:

• only n-channel devices in the circuit

• only p- channel devices in the circuit

• both n and p channel devices in the circuit

• None of the above

53. When a transistor is driven to saturation, ideally, the Vce is _____.

Answers:

• VCC

• VCC/2

• 0

• 2VCC

54. A 3-ohm load is coupled to a transistor amplifier through a step-down transformer. If the D.C resistance of the primary winding is 300Ω and the output resistance of the amplifier is 3KΩ, what should be the turn ratio for the transfer of maximum power?

Answers:

• Np/Ns=40

• Np/Ns=20

• Np/Ns=30

• Np/Ns=10

55. The ideal value of the stability factor is _____.

Answers:

• 0

• 10

• 1

• 100

56. If the A.C input to a half-wave rectifier has an R.M.S valve of 400/√2 v, the peak inverse voltage will be _____.

Answers:

• 400 v

• 400√2 v

• 800√2 v

• 800/√2 v


16 NOT Answered Yet Test Questions:

(hold on, will be updated soon)
57. Which of the following conditions must a transistor fulfill to act as an amplifier?

Answers:

• Base-emitter junction reverse biased and base-collector junction forward biased

• Base-emitter junction forward biased and base-collector junction reverse biased

• Emitter-collector junction forward biased and base- collector junction reverse biased

• Base-collector junction forward biased and emitter-collector junction reverse biased

58. The maximum value of AC voltage appearing across the secondary of a transformer in a bridge circuit using a vacuum tube is 400 v. The peak inverse voltage of the diode should be _____.

Answers:

• 200 v

• 800 v

• 400 v

• 600 v

59. Which device has the highest input impedance?

Answers:

• MOSFET

• FET

• BJT

• SCR

60. The range of LC oscillators is _____.

Answers:

• 20 HZ to 100KHZ

• 10 HZ to 20 HZ

• 100KHZ to a few GHZ

61. Which one of the following is Shockley's equation?

Answers:

• ID = IDSS [1-VGS/VP]2

• IDSS = ID [1-VGS/VP]2

• VP = IP [1-VGS/IDSS]2

• VGS = VP [1-ID/IDSS]2

62. Which of the following multivibrators is a square wave oscillator?

Answers:

• astable

• monostable

• bistable

• None of above

63. The overall gain of a multistage amplifier is 140. When negative feedback is applied, the gain is reduced to 17.5. The fraction of the output that is feedback to the input will be _____.

Answers:

• 1/30

• 1/20

• 1/10

• 1/5

64. Which of the following configurations of a transistor is preferred as an amplifier?

Answers:

• common-collector

• common- base

• common-emitter

• None of the above

65. The most commonly used semiconductor in solid state devices is _____.

Answers:

• germanium

• carbon

• silicon

• phosphorus

66. Which one of the following is a non-feedback type oscillator?

Answers:

• Wein bridge oscillator

• Hartley oscillator

• UJT relaxation oscillator

• Colpitts oscillator

67. The required gain of an amplifier for sustained oscillation in the wein bridge oscillator is _____.

Answers:

• A 2

• A 1

• A 3

• None of the above

68. Which of the following parameters is a measure of a vacuum tube's amplification capability?

Answers:

• transresistance

• impedance

• conductance

• transconductance

69. Which coupling does the final stage of a multistage amplifier use?

Answers:

• direct

• transformer

• RC

• None of the above

70. We have to match a 16-ohm speaker to an amplifier so that the effective load resistance is 10 KΩ. What should be the transformer turn ratio?

Answers:

• Np/Ns=50

• Np/Ns=25

• Np/Ns=75

• Np/Ns=12.5

71. The resonant circuit has ___________ impedance at the resonant frequency.

Answers:

• a capacitive

• an inductive

• a resistive

72. Which of the following is used to provide current in vacuum tubes?

Answers:

• protons

• ions

• electrons

• neutrons


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Darsh July 29, 2015
very like this site, 

thank you for updates. Almost pass all my speciality tests
Administrator July 30, 2015
good luck!