cns-ee2 []

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CNS-EE2: Electronics Circuits (Diodes & Transistors) 1. When the diode is supplied with a forward direction potential but with a magnitude less than the threshold voltage of the diode, still it will not “turn-on” and will only allow a very small amount of current to pass. This very small current is known as Ans. cut-off current 2. As the operating temperature of a reverse-biased diode is increased, its leakage of reverse saturation current will Ans. increase exponentially 3. Calculate the new threshold voltage of a germanium diode when it operates at 100 ˚C. Ans. 0.113 V 4. A silicon diode has a reverse saturation current of 50 nA at room temperature. If the operating temperature is raised by 50 ˚C, what is now the reverse saturation current? Ans. 1.66 μA 5. In every increase of 10 ˚C in the operating temperature of a diode will cause its reverse saturation current to Ans. double 6. The resistance of the diode that is significant when operating with a small ac signal. Ans. dynamic resistance 7. When a diode is used in large ac voltages, the resistance that is to be considered is Ans. average resistance 8. At forward bias condition, what will happen to the diode resistance when the applied voltage is increased? Ans. will decrease 9. When a diode is reverse biased the depletion region widens, since it is in between positively charge holes and negatively charge electrons, it will have an effect of a capacitor, this capacitance is called what? Ans. transition capacitance 10. In a semiconductor diode, the total capacitance, that is the capacitance between terminals and electrodes, and the internal voltage variable capacitance of the junction is called Ans. diode capacitance 11. What capacitance is significant when the diode is forward biased? Ans. diffusion capacitance 12. The time taken by the diode to operate in the reverse condition from forward conduction. Ans. reverse recovery time

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Page 1: CNS-EE2 []

CNS-EE2: Electronics Circuits (Diodes & Transistors)

1. When the diode is supplied with a forward direction potential but with a magnitude

less than the threshold voltage of the diode, still it will not “turn-on” and will

only allow a very small amount of current to pass. This very small current is

known as

Ans. cut-off current

2. As the operating temperature of a reverse-biased diode is increased, its leakage of

reverse saturation current will

Ans. increase exponentially

3. Calculate the new threshold voltage of a germanium diode when it operates at 100

˚C.

Ans. 0.113 V

4. A silicon diode has a reverse saturation current of 50 nA at room temperature. If

the operating temperature is raised by 50 ˚C, what is now the reverse saturation

current?

Ans. 1.66 µA

5. In every increase of 10 ˚C in the operating temperature of a diode will cause its

reverse saturation current to

Ans. double

6. The resistance of the diode that is significant when operating with a small ac

signal.

Ans. dynamic resistance

7. When a diode is used in large ac voltages, the resistance that is to be considered

is

Ans. average resistance

8. At forward bias condition, what will happen to the diode resistance when the

applied voltage is increased?

Ans. will decrease

9. When a diode is reverse biased the depletion region widens, since it is in between

positively charge holes and negatively charge electrons, it will have an effect of

a capacitor, this capacitance is called what?

Ans. transition capacitance

10. In a semiconductor diode, the total capacitance, that is the capacitance

between terminals and electrodes, and the internal voltage variable capacitance of

the junction is called

Ans. diode capacitance

11. What capacitance is significant when the diode is forward biased?

Ans. diffusion capacitance

12. The time taken by the diode to operate in the reverse condition from forward

conduction.

Ans. reverse recovery time

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13. In operating a diode at high-speed switching circuits, one of the most

important parameters to be considered is

Ans. reverse recovery time

14. The time required for forward voltage or current to reach a specified value

after switching the diode from its reverse-to-forward-biased state.

Ans. forward recovery time

15. A certain diode has a maximum power dissipation of 500 mW at room temperature

and a liner power derating factor of 5.0 mW/˚C. How much power the diode can

handle if operate4d at 50˚C?

Ans. 375 mW

16. Diode whose negative resistance depends on a specific form of quantum-

mechanical bond structure of the material.

Ans. Gunn diode

17. A diode that is especially processed so that its high current flow takes

place when the junction is reverse-biased. It is a variation of a tunnel diode.

Ans. backward diode

18. A silicon diode that exhibits a very high resistance in both directions up to

certain voltage, beyond which the unit switches to a low-resistance conducting

state. It can be viewed as two zener diodes connected back-to-back in series.

Ans. thyrector

19. A type of Reade diode that uses a heavily doped n-typed material as its drift

region.

Ans. IMPATT diode

20. A device containing more than one diode. An example is the full-wave bridge-

rectifier integrated circuit.

Ans. diode pack

21. Is the combination of the inductance of the leads and electrodes capacitance

of the junction and the resistance f the junction of a semiconductor diode

Ans. diode impedance

22. The appearance of RF current oscillations in a dc-biased slab of n-type

gallium arsenide in a 3.3 kV electric field.

Ans. Gunn effect

23. The device that is formed when an n-type and p-type semiconductors are

brought together.

Ans. junction diode

24. When the diode is supplied with a forward direction potential but with a

magnitude less than the threshold voltage of the diode, still it will not “turn-on”

and will only allow a very small amount of current of pass. This very small

current is known as

Ans. cut-off current

25. As the operating temperature of a reverse-biased diode is increased, its

leakage or reverse saturation current will

Ans. increase exponentially

Page 3: CNS-EE2 []

26. Calculate the new threshold voltage of a germanium diode when it operates at

100 ˚C.

Ans. 0.113 V

27. A silicon diode has a reverse saturation current of 50 nA at room

temperature. If the operating temperature is raised by 50 ˚C, what is now the

reverse saturation current?

Ans. 1.66 µA

28. In every increase of 10 ˚C in the operating temperature of a diode will cause

its reverse saturation current to

Ans. double

29. The resistance of the diode that is significant when operating a small ac

signal.

Ans. dynamic resistance

30. When a diode is used in large ac voltages, the resistance that is to be

considered is

Ans. average resistance

31. At forward bias condition, what will happen to the diode resistance when the

applied voltage is increased?

Ans. will decrease

32. When a diode is reverse biased the depletion region widens, since it is in

between positively charge holes and negatively charge electrons, it will have an

effect of a capacitor, this capacitance is called what?

Ans. transition capacitance

33. In a semiconductor diode, the total capacitance, that is the capacitance

between terminals and electrodes, and the internal voltage variable capacitance of

the junction is called

Ans. diode capacitance

34. What capacitance is significant when the diode is forward biased?

Ans. diffusion capacitance

35. The time taken by the diode to operate in the reverse condition from forward

conduction.

Ans. reverse recovery time

36. In operating a diode at high-speed switching circuits, one of the most

important parameters to be considered is

Ans. reverse recovery time

37. The time required for forward voltage or current to reach a specified value

after switching the diode from its reverse-to-forward-biased state.

Ans. forward recovery time

38. A certain diode has a maximum power dissipation of 500 mW at room temperature

and a linear power derating factor of 5.0 mW/˚C. How much power the diode can

handle if operated at 50˚C?

Ans. 375 mW

Page 4: CNS-EE2 []

39. Diode whose negative resistance depends on a specific form of quantum-

mechanical bond structure of the material.

Ans. Gunn diode

40. A diode that is especially processed so that its high current flow takes

place when the junction is reverse-biased. It is a variation of a tunnel diode/

Ans. backward diode

41. A silicon diode that exhibits a very high resistance in both directions up

to certain voltage, beyond which the unit switches to a low-resistance conducting

state. It can be viewed as two zener diodes connected back-to-back in series.

Ans. thyrector

42. A type of Read diode that uses a heavily doped n-type material as its drift

region.

Ans. IMPATT diode

43. A device containing more than one diode. An example is the full-wave bridge-

rectifier integrated circuit.

Ans. diode pack

44. It is the combination of the inductance of the leads and electrodes,

capacitance of the junction, and the resistance of the junction of a semiconductor

diode.

Ans. diode impedance

45. The appearance of RF current oscillations in a dc-biased slab of n-type

gallium arsenide in a 3.3 kV electric field.

Ans. Gunn effect

46. A transistor in which the base is diffused and the emitter is alloyed. The

collector is provided by the semiconductor substrate into which alloying and

diffusion are affected.

Ans. alloy-diffused transistor

47. In a semiconductor device, a p-n junction formed by alloying a suitable

material such as indium with the semiconductor.

Ans. alloy junction

48. A transistor in which one or both electrodes are created by diffusion.

Ans. diffused transistor

49. A diffused transistor in which the base, emitter, and collector electrodes

are exposed at the face of the wafer which is passivated (has an oxide layer grown

on it) to prevent leakage between surface electrodes.

Ans. diffused planar transistor

50. A bipolar transistor in which the base region has been diffused in the

semiconductor wafer.

Ans. diffused-base transistor

51. When n and p materials are both diffused into the semiconductor wafer to

provide emitter and base junctions, the transistor is called

Ans. diffused-emitter and base transistor

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52. A mesa transistor whose base is an n-type layer diffused into a p-type wafer,

the p-type wafer serves as the collector. Its emitter is a small p-type area

diffused into or alloyed with the n-layer.

Ans. diffused-mesa transistor

53. A transistor in which the semiconductor wafer is etched down in steps so the

base and emitter regions appear as physical plateaus above the collector region.

Ans. mesa transistor

54. An alloy-junction bipolar RF transistor for which the impurity concentration

is graded from high on the emitter side of the base wafer to low on the collector

side. This creates an internal drift field which accelerates current carriers and

raises the upper frequency limit of the transistor.

Ans. drift-field transistor

55. A transistor in which a thin metal crystal is overlaid on another mesa

crystal.

Ans. double-diffused epitaxial mesa transistor

56. In diffused transistors, what do you call a figure expressing the ability of

material carriers to diffuse?

Ans. diffusion constant

57. A BJT that is made by first growing the emitter and collector regions as a

crystal into which the base region is later diffused while the crystal is being

pulled.

Ans. grown-diffused transistor

58. A junction transistor made by adding different impurities successively to a

crystal in its molten state, and then slicing the resulting npn formations from the

finished crystal.

Ans. grown-junction transistor

59. A transistor having tiny emitter and collector electrodes that are formed by

alloying a thin film of impurity material with a collector and emitter pits facing

each other on opposite surfaces of the semiconductor wafer

Ans. microalloy transistor (MAT)

60. A microalloy transistor having a uniform base region that is diffused into

the wafer before the emitter and collector electrodes are produced by alloying

Ans. microalloy-diffused transistor

61. The process of growing thin oxide film on the surface of a planar

semiconductor device to protect the exposed junction(s) from contamination and

shorts.

Ans. passivation

62. A planar epitaxial transistor which has been passivated to protect the

exposed junctions.

Ans. planar epitaxial passivated transistor

63. A transistor in which the emitter, base and collector elements terminate on

the same plane of the silicon wafer.

Ans. planar transistor

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64. Usually, a pnp transistor is made by means of electrolysis and

electroplating. The emitter and collector are formed on opposite sides of a

semiconductor wafer by training two jets of electrolyte against its opposite

surfaces to etch and then electroplate the surfaces.

Ans. surface-barrier transistor

65. If the base-emitter junction is reversed biased and the base-collector

junction is forward biased, the transistor will be at what region of operation?

Ans. cut-off region

66. A transistor with β=100 is connected as common base, was found to have a

leakage current ICBO = 1 µA. If the said transistor is configured as common

emitter, what is the approximate value of its ICEO?

Ans. 100 µA

67. How is the collector cut-off or reverse saturation current ICBO related to

the emitter cut-off current IEBO?

Ans. ICBO ≈ IEBO

68. A transistor is said to be configured as common emitter if the emitter

terminal is

Ans. not used as an input nor output

69. Hybrid parameter that is usually neglected in most circuit analysis.

Ans. hr and ho

70. In most transistor input equivalent circuit it comprises of a resistor and a

Ans. voltage source

71. The graph of the product of collector-emitter voltage VCE and collector

current IC in the transistor output characteristic curve

Ans. maximum power curve

72. What will happen to the channel of a JFET as current flows to it?

Ans. skews

73. The voltage across the gate-source terminal of a FET that causes drain

current ID equals to zero.

Ans. pinch-off voltage

74. An early version of the field effect transistor in which limited control of

current carriers near the surface of a semiconductor bar or film was obtained by an

external field applied transversely.

Ans. fieldistor

75. What is the insulator used in most MOS-FET?

Ans. SiO2

76. An n-channel JFET has a drain-source saturation current IDSS = 10 mA and a

gate-source pinch-off voltage Vp = -4 V. If the applied reverse gate-source

voltage VGS = 2 V, calculate the drain current ID.

Ans. 2.5 mA

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77. Base from Shockley’s equation of a JFET, what is the drain current when the

applied voltage VGS is exactly equal to the pinch-off voltage VP?

Ans. zero

78. In MOSFET, it is the foundation upon which the device will be constructed and

is formed from a silicon base

Ans. substrate

79. The amount of voltage needed at the gate-source terminal for an enhancement

type MOSFET so that a channel can be formed for the current to flow.

Ans. threshold voltage

80. To switch off the depletion type MOSFER, the channel should be depleted.

Depletion of the channel is done by applying enough voltage across the gate-source

terminal. What do you call this voltage?

Ans. pinch-off voltage

81. In an n-channel enhancement type MOSFET, the gate voltage should be ______

with respect to the source in order to produce or enhance a channel.

Ans. positive

82. To deplete a channel from a p-channel IGFET depletion type, the gate voltage

should be ______ with respect to the source terminal.

Ans. positive

83. A junction field effect transistor has a drain saturation current of 10 mA

and a pinch-off voltage of -4 V. Calculate the maximum transconductance.

Ans. 5.0 mS

84. An n-channel MOSFET depletion type has a drain saturation current IDSS = 10

mA and a pinch-off voltage of -4 V. Calculate the maximum transconductance of the

transistor.

Ans. 5.0 mS

85. Calculate the transconductance of a p-channel MOSFET enhancement type if the

gate-source voltage VGS = -8 V, threshold voltage VT = -4 and a constant k = -0.3

mA/V2.

Ans. 2.4 mS

86. What will happen to the conductivity of the channel of an enhancement type

MOSFER if the proper gate voltage is increased?

Ans. decreases

87. The cutoff frequency of a JFET is dependent on channel length by a factor of

Ans. 1/L2

88. An n-channel enhancement type MOSFET has a threshold voltage of VT = 2.5 V.

If the applied gate-source voltage VGS = 4 V, what is the approximate drain current

ID?

Ans. 0.675 mA

89. Which FET has a wide and short effective channel?

Ans. V-MOSFET

Page 8: CNS-EE2 []

90. The load line position is dependent of

Ans. the load resistance and the supply voltage

91. What will happen to the magnitude of the load line slope if the load

resistance is increased?

Ans. decreases

92. One method of stabilizing transistor circuits is to add an emitter

resistance. This resistance causes the load line slope to

Ans. become less negative

93. The power gain that is lost due to the emitter bias resistor can be recovered

by

Ans. shunting a by-pass capacitor

94. When a capacitor is involved at the output circuit of a transistor amplifier

it would mean

Ans. a different dc and ac load line

95. How does the emitter by-pass capacitor affect the dc load line?

Ans. it does not affect the dc load line

96. In analyzing the quiescent currents and voltages, on what load line do you

refer?

Ans. dc load line

97. The position of the Q-point along the load line is greatly affected by what

component?

Ans. base-resistor

98. What will happen to the position of the Q-point if the resistance base-

resistor is increased?

Ans. it moves downward

99. For a fixed-biased transistor circuit, what will happen to the Q-point when

the operation temperature rises?

Ans. it moves upward

100. For a battery operated transistor circuit, where is a good position of the Q-point

in order to minimize battery consumption?

Ans. near cutoff region

101. When troubleshooting a typical transistor amplifier in the active region, VCE is

usually _____ the supply voltage VCC.

Ans. about 25% to 75% of

102. Calculate the stability factor due to the variation of ICBO from 1 nA to 21 nA when

the temperature changes from room temperature to 100 ˚C. The change in collector-

current due to the change of ICBO was found to be 0.5 µA.

Ans. 25

103. The higher the stability factor means, a transistor circuit that is more sensitive

to temperature

Ans. variations, and therefore undesired

Page 9: CNS-EE2 []

104. What stability factor that gives the highest value for a typical voltage-divider

bias transistor circuit?

Ans. S (ICO)

105. Calculate the change in the collector current due to the change in ICO for a

transistor circuit at 100 ˚C. ICO at room temperature is given to be 0.1 nA and

increases to 20 nA at 100 ˚C. The circuit has a stability factor S(ICO) = 25.

Ans. 0.5 µA

106. For most common-emitter configuration with different methods of biasing, what is

the maximum stability factor due to the change of the reverse saturation current ICO?

Ans. β + 1

107. What is the approximate output impedance of a common-emitter fixed-bias

configuration? The collector resistance RC is the only load resistance/

Ans. RC

108. A FET is biased with a voltage-divider configuration and is set at the active

region. Ideally, what is the gate current?

Ans. 0 mA

109. What type of FET that can be biased with both negative and positive gate-source

voltage VGS?

Ans. MOSFET depletion type

110. How do you classify an amplifier used to amplify either amplitude modulated (AM) or

frequency modulated (FM) signals?

Ans. class S

111. Which class of amplifiers that have the highest efficiency?

Ans. class D

112. Transistorized class C power amplifiers will usually have an efficiency of

Ans. 33%

113. For pulse-amplification, class D amplifier is mostly used. How efficient is a

class D amplifier?

Ans. its efficiency reaches over 90%

114. The Q-point of a class D amplifier can be set or positioned at what region in the

load line?

Ans. any of these

115. What do you call an amplifier that is biased to class C but modulates over the same

portion of the curve as if it were biased to class B?

Ans. class BC

116. Two class B amplifiers connected such that one amplifies the positive cycle and the

other amplifies the remaining negative cycle. Both output signals are then coupled

by a transformer to the load.

Ans. transformer-coupled push-pull amplifier

117. A push-pull amplifier that uses npn and pnp transistors to amplify the positive and

negative cycles respectively.

Ans. complementary-symmetry amplifier

Page 10: CNS-EE2 []

118. A push-pull amplifier that uses either npn or pnp as its final stage. The circuit

configuration looks like the complementary-symmetry.

Ans. quasi-complementary push-pull amplifier

119. Distortion that is due to the inability of an amplifier to amplify equally well all

the frequencies present at the input signal/

Ans. amplitude distortion

120. Calculate the second harmonic distortion for an output signal having a fundamental

amplitude of 3 V and a second harmonic amplitude of 0.3 V.

Ans. 10 %

121. An amplifier has the following percent harmonic distortions: D2 = 10%, D3 = 5% and

D4 = 1%. What is the amplifier %THD?

Ans. 11.22%

122. T-equivalent circuit for transistor is considered as a _____ representation/

Ans. physical

123. What transistor model that uses a parameter value that is directly derived from the

operating condition?

Ans. re or dynamic model

124. The transistor model that is best suited for high frequency applications/

Ans. Giacolleto model

125. Another name of Giacolleto model for transistor modeling is

Ans. hybrid-pi model

126. What model is appropriate to use, if for a given transistor amplifier, beta (β) is

the only parameter available and we want to solve for its input and output

impedances?

Ans. dynamic model

127. When the transistor is operating at saturation region, dc-current is best

determined by using what model?

Ans. Ebers-Moll model

128. A two-stage transistor amplifier in which the output collector of the first stage

provides input to the emitter of the second stage. The final output is then taken

from the collector of the second or last stage.

Ans. cascode configuration

129. Famous transistor amplifier configuration designed to eliminate the so called

Miller effect.

Ans. cascode amplifier

130. Transistor arrangement that operates like a darlington but uses a combination of

pnp and npn transistors instead of both npn.

Ans. feedback pair