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# Test answers for Electronic Design Test 2020

(14 / 54, CL) Last updated: February 28
Upwork (oDesk) • Electronics

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`1. A Colpitt’s oscillator uses _____.`

• 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 _____.`

• 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?`

• 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?`

• 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?`

• 50%

• 25.73%

• 39.73%

• 30.11%

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

• 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?`

• 1KΩ

• 2KΩ

• 3KΩ

• 4KΩ

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

• 0.2

• 0.1

• 0.5

• 0.8

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

• 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 _____.`

• 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 _____.`

• unilateral and astable

• bilateral and astable

• unilateral and bistable

• bilateral and bistable

`12. An Emitter follower is used for _____.`

• 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?`

• 1000KHz

• 1200KHz

• 1600KHz

• 2000KHz

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

• 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 _____.`

• all frequencies

• frequencies up to 300Hz

• frequencies up to 30KHz

• frequencies up to 300KHz

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

• 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 _____.`

• 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?`

• 0.6 Vpp

• 0.3 Vpp

• v3 Vpp

• v2 Vpp

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

• lower than

• higher than

• equal to

• None of the above

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

• 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?`

• 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?`

• 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?`

• 100

• 99

• 33

• 6

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

• 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?`

• 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)`

• 9W

• 12W

• 10.13W

• 20.26W

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

• 0 and 1

• 1 and 2

• 2 and 3

• 3 and 4

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

• SCR

• UJT

• Diac

• Triac

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

• slightly more than one

• more than 100

• less than one

• None of the above

`30. The Hall Effect voltage in intrinsic silicon _____.`

• 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.```

• A

• B

• C

• D

`32. An ideal amplifier has the _____.`

• 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?`

• 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?`

• 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 ________.```

• 15ohm

• 24ohm

• 27ohm

• 45ohm

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

• Finite

• Zero

• Infinite

• Unity

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

• a digital clock

• an audio signal generator

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

• 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 _____.`

• 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 )`

• 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?`

• Step-up

• Step-down

• Cannot be determined

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

• diffusion

• isolation

• metallization

```43. Refer to the given image:

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

• 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 _____.`

• multi-vibrator

• Hartley

• Armstrong

• Colpitt’s

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

• 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 _____.`

• 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?`

• IC-714

• IC-147

• IC-777

• IC-741

`48. Which of the following devices uses negative feedback?`

• 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?`

• 8*10-3

• 9*10-3

• 10*10-3

• 7*10-3

`50. The alpha of a transistor is _____.`

• 1

• .99

• 20

• .01

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

• CC

• CE

• CB

• All of the above

`52. An Oscillator has _____.`

• 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 _____.`

• 10A

• 50A

• 25A

• zero

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

• 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 _____.`

• 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 _____.`

• Hartley oscillator

• Colpitt’s oscillator

• untuned collector oscillator

• Wien-bridge oscillator

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

• 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 _____.`

• below 10%

• 10-20%

• 20-25%

• 25-30%

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

• -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%?`

• 1%

• 2%

• 3%

• 4%

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

• 7.8 KHz

• 3.2 KHz

• 2.5 KHz

• 780 Hz

`62. An oscillator is a _____.`

• rotating device

• static electronic device

• rotating electronic device

• electro-mechanical device

`63. Negative Feedback  in amplifiers increases _____.`

• bandwidth

• input resistance

• output resistance

• both a and b

`64. An operational amplifier can amplify ____________.`

• 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 _____.`

• 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 _____.`

• 400 KHz

• 600 KHz

• 1000 KHz

• 1600 KHz

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

• 45°

• 60°

• 90°

• 180°

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

• 2 Vm/p

• Vm/p

• Vm/2p

• 3Vm/p

```really helped me to pass some tests.