In this section of Electronic Devices and Circuits.It contain Special Purpose Diode MCQs (Multiple Choice Questions Answers).All the MCQs (Multiple Choice Question Answers) requires in depth reading of Electronic Devices and Circuits Subject as the hardness level of MCQs have been kept to advance level.These Sets of Questions are very helpful in Preparing for various Competitive Exams and University level Exams.

This Section covers below lists of topics :

1. Special Purpose Diode MCQs.
2. Zener Diode MCQs.
3. Zener Regulator MCQs.
4. Varactor Diode MCQs.
5. Optoelectronic Devices MCQs.
6. Light Emitting Diode MCQs.
7. Photo Diodes,Schottky Diode,Constant current diode MCQs

Practice it now to sharpen your concept.

PRACTICE IT NOW TO SHARPEN YOUR CONCEPT AND KNOWLEDGE

#### 1. What is true about the breakdown voltage in a zener diode?

• It decreases when current increases.
• It destroys the diode.
• It equals the current times the resistance.
• It is approximately constant.

#### 2. Which of these is the best description of a zener diode?

• It is a rectifier diode.
• It is a constant-voltage device.
• It is a constant-current device.
• It works in the forward region.

#### 3. A zener diode

• Is a battery
• Has a constant voltage in the breakdown region
• Has a barrier potential of 1 V
• Is forward-biased

#### 4. The voltage across the zener resistance is usually

• Small
• Large
• Measured in volts
• Subtracted from the breakdown voltage

#### 5. If the series resistance decreases in an unloaded zener regulator, the zener current

• Decreases
• Stays the same
• Increases
• Equals the voltage divided by the resistance

#### 6. In the second approximation, the total voltage across the zener diode is the sum of-the breakdown voltage and the voltage across the

• Source
• Series resistor
• Zener resistance
• Zener diode

#### 7. The load voltage is approximately constant when a zener diode is

• Forward-biased
• Reverse-biased
• Operating in the breakdown region
• Unbiased

#### 8. In a loaded zener regulator, which has the largest current?

• Series current
• Zener current
• None of these

#### 9. If the load resistance decreases in a zener regulator, the zener current

• Decreases
• Stays the same
• Increases
• Equals the source voltage divided by the series resistance

#### 10. If the load resistance decreases in a zener regulator, the series current

• Decreases
• Stays the same
• Increases
• Equals the source voltage divided by the series resistance

#### 11. When the source voltage increases in a zener regulator, which of these currents remains approximately constant?

• Series current
• Zener current
• Total current

• 0.7 V
• 10 V
• 14 V
• 18 V

#### 13. At high frequencies, ordinary diodes don’t work properly because of

• Forward bias
• Reverse bias
• Breakdown
• Charge storage

#### 14. The capacitance of a varactor diode increases when the reverse voltage across it

• Decreases
• Increases
• Breaks down
• Stores charges

#### 15. Breakdown does not destroy a zener diode provided the zener current is less than the

• Breakdown voltage
• Zener test current
• Maximum zener current rating
• Banier potential

#### 16. To display the digit 8 in a seven-segment indicator,

• C must be lighted
• G must be off
• F must be on
• All segments must be on

#### 17. A photodiode is normally

• Forward-biased
• Reverse-biased
• Neither forward- nor reverse biased
• Emitting light

#### 18. When the light increases, the reverse minority carrier current in a photodiode

• Decreases
• Increases
• Is unaffected
• Reverses direction

#### 19. The device associated with voltage-controlled capacitance is a

• Light-emitting diode
• Photodiode
• Varactor diode
• Zener diode

#### 20. If the depletion layer gets wider, the capacitance

• Decreases
• Stays the same
• Increases
• Is variable

#### 21. When the reverse voltage increases, the capacitance

• Decreases
• Stays the same
• Increases
• Has more bandwidth

#### 22. The varactor is usually

• Forward-biased
• Reverse-biased
• Unbiased
• Operated in the breakdown region

#### 23. The device to use for rectifying a weak ac signal is a

• Zener diode
• Light-emitting diode
• Varistor
• Back diode

#### 24. Which of the following has a negative-resistance region?

• Tunnel diode
• Step-recovery diode
• Schottky diode
• Optocoupler

#### 25. A blown-fuse indicator uses a

• Zener diode
• Constant-current diode
• Light-emitting diode
• Back diode

#### 26. To isolate an output circuit from an input circuit, which is the device to use?

• Back diode
• Optocoupler
• Seven-segment indicator
• Tunnel diode

#### 27. The diode with a forward voltage drop of approximately 0.25 V is the

• Step-recovery diode
• Schottky diode
• Back diode
• Constant-current diode

#### 28. For typical operation, you need to use reverse bias with a

• Zener diode
• Photodiode
• Varactor
• All of the above

#### 29. A Zener diode is based on the principle of:

• Thermionic emission
• Tunneling of charge carriers across the junction
• Diffusion of charge carriers across the junction
• None of the above

#### 30. Silicon diode is less suited for low voltage rectifier operation because:

• Its breakdown voltage is high
• Its reverse saturation current is low
• Its cut-in voltage is high
• None of the above

#### 31. Silicon is not suitable for fabrication of light-emitting diodes because it is:

• An indirect band gap semiconductor
• A direct band gap semiconductor
• A wide band gap semiconductor
• None of the above

#### 32. For an abrupt junction Varactor diode, the dependence of the device capacitance (C), an applied reverse-bias (V) is given by:

• C ∞ Vl/3
• C ∞ VI/2
• C ∞ V-1I3
• None of the above

#### 33. A Zener diode:

• Has a high forward voltage rating
• Has a sharp breakdown at low reverse voltage
• Is useful as an amplifier
• None of the above

#### 34. Which of these is a best description of a Zener diode?

• It operates in the reverse region
• It is a constant voltage device
• It is a constant current device
• None of the above

• 10 V
• 25 V
• 15 V
• Zero

#### 36. In a standard regulator circuit that uses Zener diode 10 V, the input voltage varies from 25 to 40 V, load current varies from 10 to 20 mA, and the minimum Zener current is 5 mA, the value of the series resistance in ohms will be:

• 1500
• 1200
• 600
• None of the above

#### 37. The LED is usually made of materials like:

• GaAs
• C and Si
• GeAs
• None of the above

#### 38. Varactor diodes are used in FM receivers to obtain:

• Automatic frequency control
• Automatic gain control
• Automatic volume control
• None of the above

#### 39. No-load voltage of power supply is 100 V and full-load voltage is 80 V, the percentage of regulation is:

• 0
• 25
• 15.75
• None of the above

#### 40. Zener diodes are used as:

• Reference voltage elements
• Reference current elements
• Reference resistance
• None of the above

#### 41. Zener diodes are:

• Specially doped p–n junctions
• Normally doped p–n junctions
• Lightly doped p–n junctions
• None of the above

#### 42. Silicon diode is less suited for low voltage rectifier operation because:

• It can withstand high temperatures
• Its reverse saturation current is low
• Its breakdown voltage is high
• None of the above

#### 43. Silicon is not suitable for fabrication of light emitting diodes because it is:

• An indirect band gap semiconductor
• A direct band gap semiconductor
• A wide band gap semiconductor
• None of the above

#### 44. In an abrupt junction Varactor diode, the dependence of the device capacitance (C) and applied reverse-bias (V) is given by:

• C ∞ VI/3
• C ∞ V-1I3
• C ∞ VII2
• None of the above

#### 45. A general propose diode is more likely to suffer an avalanche breakdown rather than a Zener breakdown because:

• It is lightly doped
• It is heavily doped
• It has weak covalent bonds
• None of the above

#### 46. A Zener diode:

• Has a high forward voltage rating
• Is useful as an amplifier
• Has a sharp breakdown at low reverse voltage
• None of the above

#### 47. If the junction temperature of LED is increased the radiant output power:

• Decreases
• Increases
• Remains the same
• None of the above

#### 48. The Zener effect is valid approximately:

• Below 5 V
• Above 5 V
• Equal to 5 V
• None of these

• 360°
• 270°
• 90°
• 180°

#### 50. The transfer characteristics of a diode relates to:

• The diode current and the input voltage
• The diode current and the output voltage
• The output voltage and the input voltage
• None of the above

#### 51. The clipping action of a diode requires that its forward resistance:

• Be zero
• Have a finite value
• Be infinite
• None of the above

#### 52. For a low voltage rectification:

• Two diode full-wave rectifier is suitable
• Both bridge and full-wave rectifier are suitable
• Bridge rectifier is suitable
• None of the above

#### 53. If Vm is the peak value of an applied voltage in a half-wave rectifier with a large capacitor across the load, then PIV is:

• Vm
• Vm/2
• 2Vm
• None of the above

• 1 and 3
• 1 and 2
• 2 and 3
• 4

#### 55. The most significant component of ripple voltage in a half-wave rectifier is contained in:

• Fundamental frequency
• Second harmonic
• DC component
• None of the above

#### 56. The disadvantages of capacitor input LC filter are:

• High cost, more weight and external field produced by a series inductor
• High cost, less weight
• Low cost, more weight
• None of the above

#### 57. Larger the value of the capacitor filter:

• Smaller the dc voltage across the load
• Longer the time that current pulse flows through the diode
• Larger the peak current in the rectifying diode
• None of the above

#### 58. Which rectifier requires four diodes?

• Half-wave voltage doublers
• Full-wave voltage doublers
• Full-wave bridge circuit
• None of the above

#### 59. Zener diode has a

• High forward voltage rating
• Negative resistance
• High amplification
• Sharp breakdown voltage at low reverse voltage

#### 60. Zener diode is used as

• An amplifier
• A voltage regulator
• A coupler
• A rectifier

#### 61. Zener diode is operated in

• Breakdown region
• Forward characteristics region
• Both a and b
• None of these

#### 62. The output voltage of a zener diode rated as 12 volt  10% tolerance is

• 12.2 to 11.8 volt
• 13.2 to 10.8 volt
• Only 12 volt
• None of these

#### 63. A  veractor diode is optimized for

• High output voltage
• High output current
• It’s a variable capacitance
• It’s variable inductance

#### 64. When the reverse bias potential is increased across of varactor diode

• Width of depletion layer increases which capacitance
• Width of the depletion layer increases which decreases the capacitance
• Width of the depletion layer decreases which decreases the capacitance
• Width of the depletion layer decreases with increases the capacitance

#### 65. The light emitting diode LED is

• Si
• Ge
• GaAsP
• None of these

#### 66. The material used for construction of LED is

• Si
• Ge
• GaAsP
• None of these

• 0.25 volt
• 0.7 volt
• 0.3 volt
• 1.7 volt

#### 68. Diode which has zero breakdown voltage is known as

• Zener diode
• Scott key diode
• Backward diode
• Tunnel diode
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