In this section of Electronic Devices and Circuits.It contain Semiconductor 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 :**

- Semiconductor Diode MCQs.
- Diode Fundamentals MCQs.
- Diode Circuits MCQs.
- Diode Theory MCQs.
- Half wave recifier, full wave rectifier ,Centre-tap full wave rectifier,Full-wave bridge rectifier MCQs.
- Ripple factor, MCQs.
- Filter circuits,Shunt capacitor filter,Series inductor filter ,LC filter MCQs

**Practice it now to sharpen your concept.**

#### 1. How much voltage is there across the second approximation of a silicon diode when it is forward biased?

- 0
- 0.3 V
- 0.7 V
- 1 V

#### 2. How much current is there through the second approximation of a silicon diode when it is reverse biased?

- 0
- 1 mA
- 300 mA
- None of the above

#### 3. How much forward diode voltage is there with the ideal diode approximation?

- 0
- 0.7 V
- More than 0.7 V
- 1 V

#### 4. The bulk resistance of a 1N4001 is

- 0
- 0.23 ohm
- 10 ohm
- 1 kohm

#### 5. If the bulk resistance is zero, the graph above the knee becomes

- Horizontal
- Vertical
- Tilted at 450
- None of the above

#### 6. The ideal diode is usually adequate when

- Troubleshooting
- Doing precise calculations
- The source voltage is low
- The load resistance is low

#### 7. The second approximation works well when

- Troubleshooting
- Load resistance is high
- Source voltage is high
- All of the above

#### 8. The only time you have to use the third approximation is when

- Load resistance is low
- Source voltage is high
- Troubleshooting
- None of the above

#### 9. If N1/N2 = 2, and the primary voltage is 120 V, what is the secondary voltage?

- 0 V
- 36 V
- 60 V
- 240 V

#### 10. In a step-down transformer, which is larger?

- Primary voltage
- Secondary voltage
- Neither
- No answer possible

#### 11. A transformer has a turns ratio of 4: 1. What is the peak secondary voltage if 115 V rms is applied to the primary winding?

- 40.7 V
- 64.6 V
- 163 V
- 650 V

#### 12. With a half-wave rectified voltage across the load resistor, load current flows for what part of a cycle?

- 0 degrees
- 90 degrees
- 180 degrees
- 360 degrees

#### 13. Line voltage may be from 105 V rms to 125 rms in a half-wave rectifier. With a 5:1 step-down transformer, the maximum peak load voltage is closest to

- 21 V
- 25 V
- 29.6 V
- 35.4 V

#### 14. The voltage out of a bridge rectifier is a

- Half-wave signal
- Full-wave signal
- Bridge-rectified signal
- Sine wave

#### 15. If the line voltage is 115 V rms, a turns ratio of 5: 1 means the rms secondary voltage is closest to

- 15 V
- 23 V
- 30 V
- 35 V

#### 16. What is the peak load voltage in a full-wave rectifier if the secondary voltage is 20 V rms?

- 0 V
- 0.7 V
- 14.1 V
- 28.3 V

#### 17. We want a peak load voltage of 40 V out of a bridge rectifier. What is the approximate rms value of secondary voltage?

- 0 V
- 14.4 V
- 28.3 V
- 56.6 V

#### 18. With a full-wave rectified voltage across the load resistor, load current flows for what part of a cycle?

- 0 degrees
- 90 degrees
- 180 degrees
- 360 degrees

#### 19. What is the peak load voltage out of a bridge rectifier for a secondary voltage of 15 V rms? (Use second approximation.)

- 9.2 V
- 15 V
- 19.8 V
- 24.3 V

#### 20. If line frequency is 60 Hz, the output frequency of a half-wave rectifier is

- 30 Hz
- 60 Hz
- 120 Hz
- 240 Hz

#### 21. If line frequency is 60 Hz, the output frequency of a bridge rectifier is

- 30 Hz
- 60 Hz
- 120 Hz
- 240 Hz

#### 22. With the same secondary voltage and filter, which has the most ripple?

- Half-wave rectifier
- Full-wave rectifier
- Bridge rectifier
- Impossible to say

#### 23. With the same secondary voltage and filter, which produces the least load voltage?

- Half-wave rectifier
- Full-wave rectifier
- Bridge rectifier
- Impossible to say

#### 24. If the filtered load current is 10 mA, which of the following has a diode current of 10 mA?

- Half-wave rectifier
- Full-wave rectifier
- Bridge rectifier
- Impossible to say

#### 25. If the load current is 5 mA and the filter capacitance is 1000uF, what is the peak-to-peak ripple out of a bridge rectifier?

- 21.3 pV
- 56.3 nV
- 21.3 mV
- 41.7 mV

#### 26. The diodes in a bridge rectifier each have a maximum dc current rating of 2 A. This means the dc load current can have a maximum value of

- 1 A
- 2 A
- 4 A
- 8 A

#### 27. What is the PIV across each diode of a bridge rectifier with a secondary voltage of 20 V rms?

- 14.1 V
- 20 V
- 28.3 V
- 34 V

#### 28. If the secondary voltage increases in a bridge rectifier with a capacitor-input filter, the load voltage will

- Decrease
- Stay the same
- Increase
- None of these

#### 29. If the filter capacitance is increased, the ripple will

- Decrease
- Stay the same
- Increase
- None of these

#### 30. In a *p–n junction* diode:

1.The depletion capacitance increases with increase in the reverse-bias |

2.The depletion capacitance decreases with increase in the reverse-bias |

3.The diffusion capacitance increases with increase in the forward-bias |

4.The diffusion capacitance is much higher than the depletion capacitance when it is forward-biased |

- 1 and 3
- 3 and 4
- 1 only
- 2 , 3 and 4

The depletion capacitance decreases with increase in the reverse-bias

The diffusion capacitance increases with increase in the forward-bias

The diffusion capacitance is much higher than the depletion capacitance when it is forward-biased

#### 31. A *p–n* junction in series with a 100 ohms resistor is forward-biased so that a current of 100 mA flows. If the voltage across this combination is instantaneously reversed to 10 volt at *t* = 0 the reverse current that flows through the diode at *t* = 0 is approximately given by:

- 20 mA
- 100 mA
- 200 mA
- None of the above

#### 32. The width of the depletion region is:

- Directly proportional to doping
- Inversely proportional to doping
- Independent of doping
- None of the above

#### 33. The Fermi energy in *p–n* junction at thermal equilibrium is:

- Proportional to distance
- Directly increases with the temperature
- Invariant with respect to distance
- None of the above

#### 34. The depletion capacitance, *C*_{j} of an abrupt *p–n* junction with constant doping on either side varies with reverse bias, *V*_{R}, as:

_{j}

_{R}

*C*_{j}αV_{R}^{3}*C*_{j}µV_{R}^{–2}*C*_{j}αV_{R}^{–1/2}- None of the above

*C*

_{j}αV_{R}^{–1/2}

#### 35. Gold is often diffused into silicon *p–n* junction devices to:

- Is proportional to the square of the recombination rate
- Is proportional to the cube of the recombination rate
- Make silicon a direct gap semiconductor
- None of the above

#### 36. In a forward-biased photo diode with increase in incident light intensity, the diode current:

- Increases
- Remains constant
- Decreases
- None of the above

#### 37. The current through a *p*–*n* junction diode with V volts applied to the *p*-region relative to the *n*-region (where *I*_{O} is the reverse saturation current of the diode, *η* the ideality factor, *K* the Boltzmann constant, *T* the absolute temperature and *e* the magnitude of charge on an electron) is:

_{O}

*I*_{0}(–*eV*/*e*–1)^{mKT}*I*_{0}(1 +*e*^{–eV/mKT})*I*_{0}(1 –*e*^{eV}^{/mKT})*I*_{0}[exp(*eV*/*ηk*) –1]_{B}T

*I*

_{0}[exp(

*eV*/

*ηk*) –1]

_{B}T#### 38. The varactor diode is:

- Voltage-dependent resistance
- Voltage-dependent capacitance
- Voltage-dependent inductor
- None of the above

#### 39. The electric field in abrupt *p–n* junction is:

- Linear function of distance
- Parabolic function of distance
- Independent of distance
- None of the above

#### 40. In a linearly-graded *p–n* junction the doping concentration:

- Changes abruptly at the junction
- Varies linearly with distance from junction
- Has a similar variation in junction capacitance with applied voltage
- (a), (b) and (c)

#### 41. A *p–n* junction, which is produced by recrystallisation on a base crystal, from a liquid phase of one or more components and the semiconductor is called:

- Doped junction
- Alloy junction
- Fused junction
- None of the above

#### 42. In an open circuit *p–n* junction, the energy band diagram of *n*-region shifts relative to that of *p*-diagram:

- Downward by
*Eo* - Upward by
*Eo* - Remains invariant
- Upward by 2
*Eo*

*Eo*

#### 43. The contact potential *V*_{0} in a *p*–*n* diode equals:

_{0}

*V*ln(_{T}*N*/_{A}N_{D}*n*_{i}^{2})*V*exp(n_{T}_{i}^{2}/*N*)_{A}N_{D}*V*ln(n_{T}_{i}^{2}/*N*)_{A}N_{D}*V*ln(_{T}*N*)_{A}N_{D}

*V*ln(

_{T}*N*/

_{A}N_{D}*n*

_{i}^{2})

#### 44. Each diode of full wave centre-tapped rectifier conducts for:

- 45
^{0}only - 180
^{0}only - 360
^{0}complete period - 270
^{0}only

^{0}only

#### 45. Bulk resistance of a diode is:

- The sum of resistance values of n-material and p-material
- The sum of half the resistance value of n-material and p-material
- Equivalent resistance of the resistance value of p- and n-material is parallel
- None of the above

#### 46. In unbiased *p*–*n* junction, thickness of depletion layer is of the order of:

- 10
^{–10}*m* - 50
*µm* - 0.5
*µm* - 0.005
*µm*

*µm*

#### 47. In a diode circuit, the point where the diode starts conducting is known as:

- Cut-in point
- Cut-out point
- Knee point
- Cut-off point

#### 48. A Zener diode should have:

- Heavily doped p- and n-regions
- Lightly doped p- and n-regions
- Narrow depletion region
- Both (a) and (c)

#### 49. When a diode is forward-biased, the recombination of free electron and holes may produce:

- Heat
- Light
- Radiation
- All of the above

#### 50. In a linear-graded junction, the width of the depletion layer varies as:

*V*_{j}*V*_{j}^{–2}- (
*V*)_{j}^{1/3} - None of the above

*V*)

_{j}^{1/3}

#### 51. The transition capacitance in step-graded junction varies as:

*C*_{j}αV_{R}^{3}*C*_{j}αV_{R}^{–1/2}*C*–_{j}αV_{R}^{1/3}- None of the above

*C*–

_{j}αV_{R}^{1/3}

#### 52. In a *p*–*n* diode, for constant value of current at room temperature, *d*_{v}/*d*_{t} varies approximately at the rate of:

_{v}

_{t}

- –2.5 mV/
^{0}C - –25mV/
^{0}C - 2.5mV/
^{0}C - 25mV/
^{0}C

^{0}C

#### 53. Total space–charge neutrality is given by:

- |
*Q*| =*eAN*=_{d}x_{n}*e*/*A*(*N*)_{a}x_{p} - |
*Q*| =*eAx*/_{n}*N*=_{d}*eAx*_{p}/N_{D} - |
*Q*| =*eAN*=_{d}x_{n}*eAN*_{a}x_{p} - |
*Q*| =*eAN*=_{d}x_{n}*eAN*_{a}x_{p}^{2}

*Q*| =

*eAN*=

_{d}x_{n}*eAN*

_{a}x_{p}#### 54. The reverse saturation current *I*_{s} is given by:

_{s}

*I*≡_{s}*AJ*≡_{s}*Ae*(*D*/_{p}*L*+_{p}*D*/_{n}*L*)_{n}*I*≡_{s}*AJ*≡_{s}*A*ln(*D*/_{p}p_{n}*L*–_{p}*D*/_{n}n_{p}*L*)_{n}*I*≡_{s}*AJ*≡_{s}*A*(*D*/_{p}p_{n}*L*+_{p}*D*/_{n}n_{p}*L*)_{n}^{2}*I*≡_{s}*AJ*≡_{s}*Ae*(*D*/_{p}p_{n}*L*+_{p}*D*/_{n}n_{p}*L*)_{n}

*I*≡

_{s}*AJ*≡

_{s}*Ae*(

*D*/

_{p}p_{n}*L*+

_{p}*D*/

_{n}n_{p}*L*)

_{n}#### 55. Potential barrier PN junction is established due to the charges on either side of the junction. the charges are

- Majority carriers
- Minority carriers
- Both a and b
- Donor and acceptor ions

#### 56. In a PN junction holes diffuse from the p-region to n-region because

- The movie across the junction by the potential difference
- Free electrons available in the n-region attract them
- The holes concentration in the p-region is Greater as compared to n- region
- All of these

#### 57. In a crystal diode, the barrier potential offers opposition to only

- Free electron in n- region
- Holes in p-region
- Majority carriers in both regions
- Minority carriers in both regions

#### 58. When reverse bias is applied to a crystal diode, it

- Raises the potential barrier
- Lower the potential barrier
- Increase the majority carrier current greatly
- None of these

#### 59. At reverse bias, the number of minority Carriers crossing the junction of a diode depends primarily on the

- Concentration of doping impurities
- Rate of thermal generation of electron hole pair
- Magnitude of the potential barrier
- All of these

#### 60. When a forward bias is applied to a crystal diode, it

- Raises the potential barrier
- Lower the potential barrier
- Reduces the minority carrier current to zero
- None of these

#### 61. Avalanche breakdown in The Crystal diode occurs when

- The potential barrier is reduced to zero
- Forward current exceeds a certain value
- Reverse bias exceeds a certain value
- All of these

#### 62. When a PN junction is forward biased

- Electrons in the n- region are injected into the p-region
- Holes in the p-region are injected into the n- region
- Both a and b
- None of these

#### 63. Under normal operating voltage, the reverse current in a silicon diode is about

- 10 Milli amperes
- 1 micro ampere
- 1000 micro ampere
- None of these

#### 64. In a half wave rectifier, the load current flows

- Only for the positive of cycle of the input signal
- For less than half cycle of the input signal
- For more than half cycle of the input signal
- For whole cycle of the input signal

#### 65. in a full wave rectifier, the current in each diode flows for

- Whole cycle of the input signal
- Half cycle of the input signal
- More than half cycle of the input signal
- None of these

#### 66. The full wave rectification, if the input frequency is 50 Hertz, the output frequency will be

- 50 Hertz
- 75 Hertz
- 100 Hertz
- 200 Hertz

#### 67. In a Centre tapped full wave rectifier, if V_{m} is the peak voltage between the centre tap and one end of the secondary, the maximum voltage coming across the reverse biased diode is

_{m}

- Vm
- 2Vm
- 1/2 Vm
- Vm/√2

#### 68. the maximum efficiency of full wave rectification is

- 40.6%
- 100%
- 81.2%
- 85.6%

#### 69. 15 in a bridge type full wave rectifier, if V_{m } is the peak voltage across the secondary of the transformer ,the maximum voltage coming across each reverse-biased diode is

_{m }

- Vm
- 2Vm
- 1/2 Vm
- Vm/√2

#### 70. When the graph of current versus voltage is a straight line, the device is referred to as

- Active
- Linear
- Nonlinear
- Passive

#### 71. What kind of device is a resistor?

- Unilateral
- Linear
- Nonlinear
- Bipolar

#### 72. What kind of a device is a diode?

- Bilateral
- Linear
- Nonlinear
- Unipolar

#### 73. How is a non-conducting diode biased?

- Forward
- Inverse
- Poorly
- Reverse

#### 74. When the diode current is large, the bias is

- Forward
- Inverse
- Poor
- Reverse

#### 75. The knee voltage of a diode is approximately equal to the

- Applied voltage
- Barrier potential
- Breakdown voltage
- Forward voltage

#### 76. The reverse current consists of minority-carrier current and

- Avalanche current
- Forward current
- Surface-leakage current
- Zener current