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Test answers for Electronic Design Test 2016

(14 / 54, CL) Last updated: February 28
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14 Answered Test Questions:

1. A Colpitt’s oscillator uses _____.

Answers:

• a tapped inductor

• a tapped capacitor

• no tapped inductor or capacitor

• both a tapped inductor and a tapped capacitor

2. A Wien-bridge oscillator is basically a _____.

Answers:

• pulse generator

• sine-wave generator

• square-wave generator

• triangular wave generator

3. A voltage V=300cos100t is applied to a half wave rectifier with RL =5KΩ. The rectifier may be represented by an ideal diode in series with a resistance of 1KΩ. What would be the ripple factor in this case?

Answers:

• 0

• 100%

• 110.21%

• 121.13%

4. A bridge rectifier circuit has secondary voltage of 12Vr.m.s. Assume secondary resistance and diode forward resistance to be negligible. The load resistance is 100Ω. What would be the peak load current?

Answers:

• 0.169 Amp

• 0.108 Amp

• 0.118 Amp

• 11.8 Amp

5. A half wave rectifier supplies power to 1000Ω load from a 110V (r.m.s) source of supply. If the forward resistance of the diode is 20Ω. What would be the efficiency of the rectifier?

Answers:

• 50%

• 25.73%

• 39.73%

• 30.11%

6. After triggering an SCR , the gate pulse is removed. the current in the SCR will _____.

Answers:

• remain the same

• immediately fall to zero

• rise-up

• rise a little and fall to zero

7. A feedback amplifier has an internal gain = 40dB and a feedback factor = 0.05, if the input impedance of this circuit is 12KΩ. What would have been the input impedance of the amplifier if the feedback had not been present?

Answers:

• 1KΩ

• 2KΩ

• 3KΩ

• 4KΩ

8. An amplifier has a gain of 10 without feedback. To make it oscillate, ß must be _____.

Answers:

• 0.2

• 0.1

• 0.5

• 0.8

9. For designing a Push-Pull amplifier, the type of transistors should be _____.

Answers:

• one should be p-n-p and the other should be n-p-n

• Both should be either p-n-p or n-p-n

• both should be n-p-n only

• All of the above

10. A crystal oscillator provides very stable frequency because of _____.

Answers:

• the high stability of the crystal

• the rigid crystal structure

• the low XL/R ratio of the crystal

• the high Q of the crystal

11. A transistor is a semiconductor switch which is _____.

Answers:

• unilateral and astable

• bilateral and astable

• unilateral and bistable

• bilateral and bistable

12. An Emitter follower is used for _____.

Answers:

• high current gain

• high voltage gain

• impedance matching

• high power gain

13. An amplifier has a bandwidth of 200KHz and a voltage gain of 100. What will be the new bandwidth if 5% negative feedback is introduced?

Answers:

• 1000KHz

• 1200KHz

• 1600KHz

• 2000KHz

14. A differentiator converts a linear ramp into a _____.

Answers:

• triangular wave

• square wave

• sinusoidal wave

• constant D.C signal


54 NOT Answered Yet Test Questions:

(hold on, will be updated soon)
15. Most SCRs can be turned-off by voltage reversal during the negative half-cycle of the A.C supply for _____.

Answers:

• all frequencies

• frequencies up to 300Hz

• frequencies up to 30KHz

• frequencies up to 300KHz

16. One of the ways to destroy a diode is _____.

Answers:

• to exceed the current limit in forward direction

• to apply a small voltage in the reverse direction

• to dip it in water

• to drop on the floor

17. For class-AB power amplifier, the output current flows _____.

Answers:

• for more than 90° but less than 180°

• for more than 270° but less than 360°

• for more than 180° but less than 360°

• for more than 45° but less than 90°

18. What would be the output of a voltage follower if it has an input of 0.3Vpp?

Answers:

• 0.6 Vpp

• 0.3 Vpp

• v3 Vpp

• v2 Vpp

19. The dV/dt capability of the thyristor is _____ that of the triac.

Answers:

• lower than

• higher than

• equal to

• None of the above

20. In a class-B power amplifier, the output signal is obtained only _____.

Answers:

• for one half cycle period of the input A.C signal

• for full cycle period of the input A.C signal

• for quarter cycle period of the input A.C signal

21. Which of the following does not cause permanent damage to an SCR?

Answers:

• High current

• High rate of the rise of the current

• High temperature rise

• High rate of the rise of the voltage

22. Which semiconductor power device out of the following is not a current triggered device?

Answers:

• Thyristor

• GTO

• Triac

• MOSFET

23. An emitter follower is found to have a voltage gain of 0.99. What would be the value of ß for its transistors?

Answers:

• 100

• 99

• 33

• 6

24. Both positive and negative feedbacks are employed in _____.

Answers:

• a Hartley Oscillator

• a Colpitt’s Oscillator

• a Tuned – Collector Oscillator

• a Wien Bridge Oscillator

25. Which one of the following amplifiers has the highest efficiency?

Answers:

• Class-A

• Class-B

• Class-C

• Class-AB

26. How much power is dissipated in the individual transistor of a Class-B push-pull amplifier if Vcc=20V and R1=4Ω (primary resistance)

Answers:

• 9W

• 12W

• 10.13W

• 20.26W

27. In a negative feedback circuit , the feedback factor is always between _____.

Answers:

• 0 and 1

• 1 and 2

• 2 and 3

• 3 and 4

28. The transistor equivalent of the thyratron tube is _____.

Answers:

• SCR

• UJT

• Diac

• Triac

29. The loop gain of the oscillator to start with is _____.

Answers:

• slightly more than one

• more than 100

• less than one

• None of the above

30. The Hall Effect voltage in intrinsic silicon _____.

Answers:

• is positive

• is zero

• is negative

• changes the sign on the application of the magnetic field

31. D.C current of a half wave rectifier is _____.

Here, Im = peak value of the input current.

Answers:

• A

• B

• C

• D

32. An ideal amplifier has the _____.

Answers:

• noise figure of 0dB

• noise figure of more than 0dB

• noise factor of unity

• noise figure of less than 1dB

33. In the transistor circuit shown in the figure, the collector-to-ground voltage is 20V. Which of the following is the probable cause of the error?

Answers:

• The collector-emitter terminals short-circuited

• The emitter to ground connection open

• The 10KΩ resistor open

• The collector- base terminal short-circuited

34. Which one of the following amplifiers is designed to operate digital signals?

Answers:

• Class-A

• Class-B

• Class-C

• Class-D

35. Refer to the given image:

The circuit shown in the image has a zener regulated D.C power supply. Assuming that the zener diode is ideal, the minimum value of RL due to which the output voltage would remain constant will be ________.

Answers:

• 15ohm

• 24ohm

• 27ohm

• 45ohm

36. What would be the input impedance of an ideal op-amp?

Answers:

• Finite

• Zero

• Infinite

• Unity

37. The application where one is most likely to find a quartz oscillator would be _____.

Answers:

• a radio transmitter

• a radio receiver

• a digital clock

• an audio signal generator

38. The output impedance of an operational amplifier is _____.

Answers:

• very low

• very high

• dependant on the signal applied

• None of the above

39. To generate 1KHz frequency of oscillations, the most suitable circuit is _____.

Answers:

• a Hartley Oscillator

• a Colpitt’s Oscillator

• a Tuned – Collector Oscillator

• a Wien Bridge Oscillator

40. For a full wave controlled rectifier using SCR, the average load voltage is________. (VLdc )

Answers:

• Vm [1 + cosa]/2p

• Vm [1 + cosa]/p

• Vm [1 + sina]/p

• Vm [1 + sina]/2p

41. The transformer is used for impedance matching . It is expected to match 1296Ω resistance on the primary side to a 16Ω resistance on the secondary side. Calculate the required turn ratio of a transformer, what is the type of transformer?

Answers:

• Step-up

• Step-down

• Cannot be determined

42. Ultraviolet radiation is used in the IC fabrication process for _____.

Answers:

• diffusion

• masking

• isolation

• metallization

43. Refer to the given image:

The voltage at V1 and V2 of the arrangement shown in the image, will be _________ respectively.

Answers:

• 6V and 5.4V

• 5.4V and 6V

• 3V and 5.4V

• 6V and 3V

44. The oscillator circuit that uses a tapped coil in a tuned circuit is _____.

Answers:

• multi-vibrator

• Hartley

• Armstrong

• Colpitt’s

45. The most important characteristic of a crystal oscillator is _____.

Answers:

• that it has high efficiency

• that it requires very low D.C. supply

• that its output frequency is substantially constant

• that it has a low cost

46. In an amplifier , the coupling capacitors  are employed for _____.

Answers:

• limiting the bandwidth

• matching the impedances

• controlling the output

• preventing the D.C from mixing with the input or output

47. Which one of the following is a general purpose operational amplifier?

Answers:

• IC-714

• IC-147

• IC-777

• IC-741

48. Which of the following devices uses negative feedback?

Answers:

• Oscillaters

• Schmitt trigger

• Amplifiers

• All of the above

49. The voltage gain of an amplifier without feedback is 60dB. It decreases to 40dB with feedback. What will be the feedback factor?

Answers:

• 8*10-3

• 9*10-3

• 10*10-3

• 7*10-3

50. The alpha of a transistor is _____.

Answers:

• 1

• .99

• 20

• .01

51. In a complementary – symmetry amplifier, both transistors are used in the ____ configuration/s

Answers:

• CC

• CE

• CB

• All of the above

52. An Oscillator has _____.

Answers:

• A.C input

• D.C input

• Both A.C and D.C inputs

• None of the above

53. Suppose the anode current of a conducting SCR is 50A. If its gate current is reduced to one-fifth, its anode current will become _____.

Answers:

• 10A

• 50A

• 25A

• zero

54. For insulators, the forbidden gap is of the order of _____.

Answers:

• 5eV

• 1eV

• 0.1eV

• zero

55. An R-C phase shift oscillator will not produce any oscillations until and unless the voltage gain of its internal amplifier is _____.

Answers:

• more than 3 but less than 10

• less than 20

• more than 29

• None of the above

56. For generating a 1 KHz signal, the most suitable circuit is the _____.

Answers:

• Hartley oscillator

• Colpitt’s oscillator

• untuned collector oscillator

• Wien-bridge oscillator

57. If a diode is connected in anti-parallel with a thyristor, _____.

Answers:

• both the turn-off power loss and the turn-off time decrease

• the turn-off power loss decreases but the turn-off time increases

• the turn-off power loss increases but the turn-off time decreases

• None of the above

58. The latching current of an SCR is _____.

Answers:

• below 10%

• 10-20%

• 20-25%

• 25-30%

59. The gain of an inverting operational amplifier is given as _____________.

Answers:

• -R2/R1

• R1/R2

• -R1/R2

• R1/(R1+R2)

60. What would be the increase in the power delivered to the load if the total harmonic distortion is 10%?

Answers:

• 1%

• 2%

• 3%

• 4%

61. In a Wien-bridge oscillator with R=5KΩ and C=0.01µF, the frequency of oscillation will be _____.

Answers:

• 7.8 KHz

• 3.2 KHz

• 2.5 KHz

• 780 Hz

62. An oscillator is a _____.

Answers:

• rotating device

• static electronic device

• rotating electronic device

• electro-mechanical device

63. Negative Feedback  in amplifiers increases _____.

Answers:

• bandwidth

• input resistance

• output resistance

• both a and b

64. An operational amplifier can amplify ____________.

Answers:

• D.C signals only

• A.C signals only

• square waves

• None of the above

65. For a class-A power amplifier, the position of point Q is _____.

Answers:

• in the cut-off region

• just above the cut-off

• at the center of load line

• below the cut-off

66. If the RF signal is 600 KHz and the local oscillator frequency is 1000KHz, the output of the mixer will be _____.

Answers:

• 400 KHz

• 600 KHz

• 1000 KHz

• 1600 KHz

67. In a half wave rectifier, the maximum firing angle is restricted to _____.

Answers:

• 45°

• 60°

• 90°

• 180°

68. For a three phase full wave rectifier, no load D.C output is _____.

Answers:

• 2 Vm/p

• Vm/p

• Vm/2p

• 3Vm/p


Comments

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Kabir July 27, 2015
really helped me to pass some tests.

Thank you