PN Junction Diode – Exercise – 1

1. The depletion region is one which has :

(a)  Immobile charges
(b)  Mobile charges
(c)  Atoms
(d)  Molecules

Answer
Answer : (a)
Explanation
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2. The knee voltage of a PN junction diode is approximately equal to the :

(a)  Forward voltage
(b)  Applied voltage
(c)  Breakdown voltage
(d)  Potential

Answer
Answer : (d)
Explanation
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3. Diffusion capacitance is a capacitance of a :

(a)  reverse biased semiconductor diode junction caused by unequal doping
(b)  reverse biased semiconductor diode junction caused by equal doping
(c)  forward biased semiconductor diode junction caused by unequal doping
(d)  forward biased semiconductor diode junction caused by equal doping

Answer
Answer : (c)
Explanation
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4. The dynamic resistance of diode is :

(a)  constant and independent of operating voltage
(b)  constant and dependent on operating voltage
(c)  not a constant and independent of operating voltage
(d)  not a constant and dependent on operating voltage

Answer
Answer : (d)
Explanation
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5. The common method of making PN junction is known as :

(a)  diffusing
(b)  alloying
(c)  doping
(d)  biasing

Answer
Answer : (b)
Explanation
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6. The forward characteristic of a diode has a slope of approximately 50 mA/V at a desired point. The approximate incremental resistance of the diode is :

(a)  50 Ω
(b)  35 Ω
(c)  20 Ω
(d)  10 Ω

Answer
Answer : (c)
Explanation
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7. The time required to switch a PN junction from ON to OFF is equal to :

(a)  Zero
(b)  Storage time
(c)  Switching time
(d)  Transition time

Answer
Answer : (c)
Explanation
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8. Fast switching of PN junction requires :

(a)  A large current in reverse direction
(b)  Zero current in reverse direction
(c)  Reverse saturation current in reverse direction
(d)  None of the above

Answer
Answer : (a)
Explanation
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9. The storage time of a PN junction :

(a)  Decreases with increased reverse-bias
(b)  Decreases with increased forward-bias
(c)  Increases with increased reverse-bias
(d)  Increases with increased forward-bias

Answer
Answer : (a)
Explanation
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10. The delay in the switching mode operation of a PN junction diode is mainly due to :

(a)  Metallic contacts
(b)  Different doping levels
(c)  Minority charge storage in the junction during forward biased condition
(d)  Majority carriers in forward biased condition

Answer
Answer : (b)
Explanation
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11. The maximum operating frequency of a diode when used as a switch :

(a)  Depends on the diode characteristics and switching voltages
(b)  Depends on switching voltages
(c)  Depends on diode characteristics
(d)  None of the above

Answer
Answer : (a)
Explanation
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12. The saturation current in a diode depends upon :

(a)  Plate voltage
(b)  Cathode temperature
(c)  Cathode material
(d)  Separation between cathode and plate

Answer
Answer : (c)
Explanation
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13. The PN junction diode is a :

(a)  Passive device
(b)  Vacuum device
(c)  Unilateral device
(d)  Bilateral device

Answer
Answer : (c)
Explanation
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14. The time required to switch a PN junction from ON to OFF is equal to :

(a)  Zero
(b)  Storage time
(c)  Switching time
(d)  Transition time

Answer
Answer : (c)
Explanation
No answer description available for this question. Let us discuss.
15. If the PN junction is abrupt, the capacitance varies as :

(a)  Square root of reverse bias
(b)  Square of reverse bias
(c)  Cube root of reverse bias
(d)  Cube of reverse bias

Answer
Answer : (a)
Explanation
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16. Match list I and list II and select the correct one using the codes given below :
List I                                                               List II
P. Resistance                                            1. Current noise
Q. Diode                                                    2. Partition noise
R. Triode                                                   3. Shot noise
S. PN junction                                           4. Johnson noise

(a)  P- (4), Q – (1), R- (2), S- (3)
(b)  P- (2), Q – (3), R- (1), S- (4)
(c)  P- (1), Q – (2), R- (3), S- (4)
(d)  P- (4), Q – (3), R- (2), S- (1)

Answer
Answer : (d)
Explanation
No answer description available for this question. Let us discuss.
17. Capacitive effects are exhibited by PN junctions when they are :

(a)  Forward biased
(b)  Reverse biased
(c)  Either forward or reverse biased
(d)  Neither forward nor reverse biased

Answer
Answer : (c)
Explanation
No answer description available for this question. Let us discuss.
18. What is the type of capacitance effect exhibited by the PN junction, when it is reverse biased ?

(a)  Transition capacitance
(b)  Diffusion capacitance
(c)  Space charge capacitance
(d)  Drift capacitance

Answer
Answer : (b)
Explanation
No answer description available for this question. Let us discuss.
19. In a PN junction, the density of carriers is …….. near the junction and decays ………. with distance.

(a)  Low, linearly
(b)  High, linearly
(c)  Low, exponentially
(d)  High, exponentially

Answer
Answer : (d)
Explanation
No answer description available for this question. Let us discuss.
20. If CT= space change capacitance and CD= storage capacitance of PN junction diode, then :

(a)  CT= CD
(b)  CT> CD
(c)  CT< CD (d)  CT= CD =∞

Answer
Answer : (c)
Explanation
No answer description available for this question. Let us discuss.
(a) (b) (c) (d) Answer : () [/su_spoiler]
Explanation
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22. Barrier potential of PN junction decreases as temperature :

(a)  Increases
(b)  Decreases
(c)  Remains constant
(d)  Increases & then decreases

Answer
Answer : (a)
Explanation
No answer description available for this question. Let us discuss.
23. What is the type of capacitance effect exhibited by the PN junction when it is forward biased ?

(a)  Diffusion capacitance
(b)  Storage capacitance
(c)  Drift capacitance
(d)  Transition capacitance

Answer
Answer : (d)
Explanation
No answer description available for this question. Let us discuss.
24. The variable capacitance property possessed by the reverse biased PN junction is used to construct a device known as :

(a)  Zener diode
(b)  Volta caps
(c)  Gunn diode
(d)  Tunnel diode

Answer
Answer : (b)
Explanation
No answer description available for this question. Let us discuss.
25. The frequency biased PN junction diode :

(a)  Acts like an open circuit
(b)  Offers infinite resistance
(c)  Provides very high voltage drop
(d)  Conducts current easily

Answer
Answer : (d)
Explanation
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26. A PN junction is a/an :

(a)  Oscillator
(b)  Amplifier
(c)  Insulator
(d)  Rectifier

Answer
Answer : (d)
Explanation
No answer description available for this question. Let us discuss.
27. The volt-ampere relation for PN junction can be expressed as :

(a)  I = IS[e^(V/n.Vt)] –1
(b)  I = 1/IS[e^(V/n.Vt)] –1
(c)  I = IS[e^(V/n.Vt)–1]
(d)  I = IS[e^(V/n.Vt) +1]

Answer
Answer : (a)
Explanation
No answer description available for this question. Let us discuss.
28. In order to increase the recombination rate in silicon PN junction device ……… is diffused.

(a)  Aluminum
(b)  Silver
(c)  Indium
(d)  Gold

Answer
Answer : (d)
Explanation
No answer description available for this question. Let us discuss.
29. An ideal diode can be considered as an :

(a)  Amplifier
(b)  Bi-stable switch
(c)  Oscillator
(d)  Fuse

Answer
Answer : (b)
Explanation
No answer description available for this question. Let us discuss.
30. The dynamic resistance of diode is :

(a)  Constant and independent of operating voltage
(b)  Constant and dependent on operating voltage
(c)  Not a constant and independent of operating voltage
(d)  Not a constant and dependent on operating voltage

Answer
Answer : (d)
Explanation
No answer description available for this question. Let us discuss.
31. The dynamic resistance r of a diode varies as :

(a)  1/I
(b)  1/I2
(c)  I
(d)  I2

Answer
Answer : (a)
Explanation
No answer description available for this question. Let us discuss.
32. The reverse saturation current in germanium diode is of the order of :

(a)  1 nano amps
(b)  1 micro amps
(c)  1 milli amps
(d)  1 kilo amps

Answer
Answer : (b)
Explanation
No answer description available for this question. Let us discuss.
33. The diode capacitance has ……… temperature coefficient and the figure of merit has ……… temperature coefficient.

(a)  Positive, Positive
(b)  Negative, Negative
(c)  Positive, Negative
(d)  Negative, Positive

Answer
Answer : (c)
Explanation
No answer description available for this question. Let us discuss.
34. Peak inverse voltage of the diode is found to be :

(a)  Greater or equal to Vm
(b)  Small or equal to Vm
(c)  Equal to Vm
(d)  Not equal to Vm

Answer
Answer : (a)
Explanation
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35. Consider the statements
1. Ideal diode conducts with zero resistance when forward biased.
2. Ideal diode appears as an infinite resistance when reverse biased.

(a)  Only 1 is correct
(b)  Only 2 is correct
(c)  Both 1 & 2 are correct
(d)  Either 1 or 2 is correct

Answer
Answer : (c)
Explanation
No answer description available for this question. Let us discuss.
36. Boltzmann diode equation relates :

(a)  Voltage and temperature characteristics of a junction
(b)  Voltage and current characteristics of a junction
(c)  Current and temperature characteristics of a junction
(d)  Resistance and temperature characteristics of a junction

Answer
Answer : (a)
Explanation
No answer description available for this question. Let us discuss.
37. The reverse current in a diode is of the order of …………

(a)  kA
(b)  mA
(c)  microA
(d)  A

Answer
Answer : (c)
Explanation
No answer description available for this question. Let us discuss.
38. The forward voltage drop across a silicon diode is about ………….

(a)  2.5 V
(b)  3 V
(c)  10 V
(d)  0.7 V

Answer
Answer : (d)
Explanation
No answer description available for this question. Let us discuss.
39. The width of the depletion layer in a P-N junction diode :

(a)  Increases when a forward bias is applied
(b)  Decreases when a reverse bias is applied
(c)  Remain the same, irrespective of the bias
(d)  none of these

Answer
Answer : (a)
Explanation
No answer description available for this question. Let us discuss.
40. Depletion region in a diode is –

(a)  Positivity charged
(b)  Negatively charged
(c)  Completely neutral and has no charge
(d)  A charged region of positive and negative ions at the junction

Answer
Answer : (d)
Explanation
No answer description available for this question. Let us discuss.
41. In case of P-N junction diode, at high reverse bias the current rises sharply. This value of reverse bias is called –

(a)  Peak inverse ratio
(b)  Zenner voltage
(c)  Cut off bias
(d)  Saturation voltage

Answer
Answer : (b)
Explanation
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