CNS-EE2: Electronics Circuits (Diodes & 13.

In operating a diode at high-speed

Transistors) switching circuits, one of the most
important parameters to be considered is
1. When the diode is supplied with a Ans. reverse recovery time
forward direction potential but with a 14. The time required for forward voltage or
magnitude less than the threshold current to reach a specified value after
voltage of the diode, still it will not switching the diode from its reverse-to-
“turn-on” and will only allow a very forward-biased state.
small amount of current to pass. This Ans. forward recovery time
very small current is known as 15. A certain diode has a maximum power
Ans. cut-off current dissipation of 500 mW at room
2. As the operating temperature of a temperature and a liner power derating
reverse-biased diode is increased, its factor of 5.0 mW/˚C. How much power the
leakage of reverse saturation current diode can handle if operate4d at 50˚C?
will Ans. 375 mW
Ans. increase exponentially 16. Diode whose negative resistance depends
3. Calculate the new threshold voltage of a on a specific form of quantum-mechanical
germanium diode when it operates at 100 bond structure of the material.
˚C. Ans. Gunn diode
Ans. 0.113 V 17. A diode that is especially processed so
4. A silicon diode has a reverse saturation that its high current flow takes place
current of 50 nA at room temperature. when the junction is reverse-biased. It
If the operating temperature is raised is a variation of a tunnel diode.
by 50 ˚C, what is now the reverse Ans. backward diode
saturation current? 18. A silicon diode that exhibits a very
Ans. 1.66 µA high resistance in both directions up to
5. In every increase of 10 ˚C in the certain voltage, beyond which the unit
operating temperature of a diode will switches to a low-resistance conducting
cause its reverse saturation current to state. It can be viewed as two zener
Ans. double diodes connected back-to-back in series.
6. The resistance of the diode that is Ans. thyrector
significant when operating with a small 19. A type of Reade diode that uses a
ac signal. heavily doped n-typed material as its
Ans. dynamic resistance drift region.
7. When a diode is used in large ac Ans. IMPATT diode
voltages, the resistance that is to be 20. A device containing more than one diode.
considered is An example is the full-wave bridge-
Ans. average resistance rectifier integrated circuit.
8. At forward bias condition, what will Ans. diode pack
happen to the diode resistance when the 21. Is the combination of the inductance of
applied voltage is increased? the leads and electrodes capacitance of
Ans. will decrease the junction and the resistance f the
9. When a diode is reverse biased the junction of a semiconductor diode
depletion region widens, since it is in Ans. diode impedance
between positively charge holes and 22. The appearance of RF current
negatively charge electrons, it will oscillations in a dc-biased slab of n-
have an effect of a capacitor, this type gallium arsenide in a 3.3 kV
capacitance is called what? electric field.
Ans. transition capacitance Ans. Gunn effect
10. In a semiconductor diode, the total 23. The device that is formed when an n-type
capacitance, that is the capacitance and p-type semiconductors are brought
between terminals and electrodes, and together.
the internal voltage variable Ans. junction diode
capacitance of the junction is called 24. When the diode is supplied with a
Ans. diode capacitance forward direction potential but with a
11. What capacitance is significant when the magnitude less than the threshold
diode is forward biased? voltage of the diode, still it will not
Ans. diffusion capacitance “turn-on” and will only allow a very
12. The time taken by the diode to operate small amount of current of pass. This
in the reverse condition from forward very small current is known as
conduction. Ans. cut-off current
Ans. reverse recovery time
25. As the operating temperature of a temperature and a linear power derating
reverse-biased diode is increased, its factor of 5.0 mW/˚C. How much power the
leakage or reverse saturation current diode can handle if operated at 50˚C?
will Ans. 375 mW
Ans. increase exponentially 39. Diode whose negative resistance depends
26. Calculate the new threshold voltage of a on a specific form of quantum-mechanical
germanium diode when it operates at 100 bond structure of the material.
˚C. Ans. Gunn diode
Ans. 0.113 V 40. A diode that is especially processed so
27. A silicon diode has a reverse saturation that its high current flow takes place
current of 50 nA at room temperature. when the junction is reverse-biased. It
If the operating temperature is raised is a variation of a tunnel diode/
by 50 ˚C, what is now the reverse Ans. backward diode
saturation current? 41. A silicon diode that exhibits a very
Ans. 1.66 µA high resistance in both directions up to
28. In every increase of 10 ˚C in the certain voltage, beyond which the unit
operating temperature of a diode will switches to a low-resistance conducting
cause its reverse saturation current to state. It can be viewed as two zener
Ans. double diodes connected back-to-back in series.
29. The resistance of the diode that is Ans. thyrector
significant when operating a small ac 42. A type of Read diode that uses a heavily
signal. doped n-type material as its drift
Ans. dynamic resistance region.
30. When a diode is used in large ac Ans. IMPATT diode
voltages, the resistance that is to be 43. A device containing more than one diode.
considered is An example is the full-wave bridge-
Ans. average resistance rectifier integrated circuit.
31. At forward bias condition, what will Ans. diode pack
happen to the diode resistance when the 44. It is the combination of the inductance
applied voltage is increased? of the leads and electrodes, capacitance
Ans. will decrease of the junction, and the resistance of
32. When a diode is reverse biased the the junction of a semiconductor diode.
depletion region widens, since it is in Ans. diode impedance
between positively charge holes and 45. The appearance of RF current
negatively charge electrons, it will oscillations in a dc-biased slab of n-
have an effect of a capacitor, this type gallium arsenide in a 3.3 kV
capacitance is called what? electric field.
Ans. transition capacitance Ans. Gunn effect
33. In a semiconductor diode, the total 46. A transistor in which the base is
capacitance, that is the capacitance diffused and the emitter is alloyed.
between terminals and electrodes, and The collector is provided by the
the internal voltage variable semiconductor substrate into which
capacitance of the junction is called alloying and diffusion are affected.
Ans. diode capacitance Ans. alloy-diffused transistor
34. What capacitance is significant when the 47. In a semiconductor device, a p-n
diode is forward biased? junction formed by alloying a suitable
Ans. diffusion capacitance material such as indium with the
35. The time taken by the diode to operate semiconductor.
in the reverse condition from forward Ans. alloy junction
conduction. 48. A transistor in which one or both
Ans. reverse recovery time electrodes are created by diffusion.
36. In operating a diode at high-speed Ans. diffused transistor
switching circuits, one of the most 49. A diffused transistor in which the base,
important parameters to be considered is emitter, and collector electrodes are
Ans. reverse recovery time exposed at the face of the wafer which
37. The time required for forward voltage or is passivated (has an oxide layer grown
current to reach a specified value after on it) to prevent leakage between
switching the diode from its reverse-to- surface electrodes.
forward-biased state. Ans. diffused planar transistor
Ans. forward recovery time 50. A bipolar transistor in which the base
38. A certain diode has a maximum power region has been diffused in the
dissipation of 500 mW at room semiconductor wafer.
 Ans. diffused-base transistor Ans. microalloy-diffused transistor
51. When n and p materials are both diffused 61. The process of growing thin oxide film
into the semiconductor wafer to provide on the surface of a planar semiconductor
emitter and base junctions, the device to protect the exposed
transistor is called junction(s) from contamination and
Ans. diffused-emitter and base shorts.
transistor Ans. passivation
52. A mesa transistor whose base is an n- 62. A planar epitaxial transistor which has
type layer diffused into a p-type wafer, been passivated to protect the exposed
the p-type wafer serves as the junctions.
collector. Its emitter is a small p- Ans. planar epitaxial passivated
type area diffused into or alloyed with transistor
the n-layer. 63. A transistor in which the emitter, base
Ans. diffused-mesa transistor and collector elements terminate on the
53. A transistor in which the semiconductor same plane of the silicon wafer.
wafer is etched down in steps so the Ans. planar transistor
base and emitter regions appear as 64. Usually, a pnp transistor is made by
physical plateaus above the collector means of electrolysis and
region. electroplating. The emitter and
Ans. mesa transistor collector are formed on opposite sides
54. An alloy-junction bipolar RF transistor of a semiconductor wafer by training two
for which the impurity concentration is jets of electrolyte against its opposite
graded from high on the emitter side of surfaces to etch and then electroplate
the base wafer to low on the collector the surfaces.
side. This creates an internal drift Ans. surface-barrier transistor
field which accelerates current carriers 65. If the base-emitter junction is reversed
and raises the upper frequency limit of biased and the base-collector junction
the transistor. is forward biased, the transistor will
Ans. drift-field transistor be at what region of operation?
55. A transistor in which a thin metal Ans. cut-off region
crystal is overlaid on another mesa 66. A transistor with β=100 is connected as
crystal. common base, was found to have a leakage
Ans. double-diffused epitaxial mesa current ICBO = 1 µA. If the said
transistor transistor is configured as common
56. In diffused transistors, what do you emitter, what is the approximate value
call a figure expressing the ability of of its ICEO?
material carriers to diffuse? Ans. 100 µA
Ans. diffusion constant 67. How is the collector cut-off or reverse
57. A BJT that is made by first growing the saturation current ICBO related to the
emitter and collector regions as a emitter cut-off current IEBO?
crystal into which the base region is Ans. ICBO ≈ IEBO
later diffused while the crystal is 68. A transistor is said to be configured as
being pulled. common emitter if the emitter terminal
Ans. grown-diffused transistor is
58. A junction transistor made by adding Ans. not used as an input nor output
different impurities successively to a 69. Hybrid parameter that is usually
crystal in its molten state, and then neglected in most circuit analysis.
slicing the resulting npn formations Ans. hr and ho
from the finished crystal. 70. In most transistor input equivalent
Ans. grown-junction transistor circuit it comprises of a resistor and a
59. A transistor having tiny emitter and Ans. voltage source
collector electrodes that are formed by
alloying a thin film of impurity 71. The graph of the product of collector-
material with a collector and emitter emitter voltage VCE and collector
pits facing each other on opposite current IC in the transistor output
surfaces of the semiconductor wafer characteristic curve
Ans. microalloy transistor (MAT) Ans. maximum power curve
60. A microalloy transistor having a 72. What will happen to the channel of a
uniform base region that is diffused JFET as current flows to it?
into the wafer before the emitter and Ans. skews
collector electrodes are produced by
alloying
73. The voltage across the gate-source Ans. 5.0 mS
terminal of a FET that causes drain 85. Calculate the transconductance of a p-
current ID equals to zero. channel MOSFET enhancement type if the
Ans. pinch-off voltage gate-source voltage VGS = -8 V,
74. An early version of the field effect threshold voltage VT = -4 and a constant
transistor in which limited control of k = -0.3 mA/V2.
current carriers near the surface of a Ans. 2.4 mS
semiconductor bar or film was obtained 86. What will happen to the conductivity of
by an external field applied the channel of an enhancement type
transversely. MOSFER if the proper gate voltage is
Ans. fieldistor increased?
75. What is the insulator used in most MOS- Ans. decreases
FET? 87. The cutoff frequency of a JFET is
Ans. SiO2 dependent on channel length by a factor
76. An n-channel JFET has a drain-source of
saturation current IDSS = 10 mA and a Ans. 1/L2
gate-source pinch-off voltage Vp = -4 V. 88. An n-channel enhancement type MOSFET has
If the applied reverse gate-source a threshold voltage of VT = 2.5 V. If
voltage VGS = 2 V, calculate the drain the applied gate-source voltage VGS = 4
current ID. V, what is the approximate drain current
Ans. 2.5 mA ID?
77. Base from Shockley’s equation of a JFET, Ans. 0.675 mA
what is the drain current when the 89. Which FET has a wide and short effective
applied voltage VGS is exactly equal to channel?
the pinch-off voltage VP? Ans. V-MOSFET
Ans. zero 90. The load line position is dependent of
78. In MOSFET, it is the foundation upon Ans. the load resistance and the supply
which the device will be constructed and voltage
is formed from a silicon base 91. What will happen to the magnitude of the
Ans. substrate load line slope if the load resistance
79. The amount of voltage needed at the is increased?
gate-source terminal for an enhancement Ans. decreases
type MOSFET so that a channel can be 92. One method of stabilizing transistor
formed for the current to flow. circuits is to add an emitter
Ans. threshold voltage resistance. This resistance causes the
80. To switch off the depletion type MOSFER, load line slope to
the channel should be depleted. Ans. become less negative
Depletion of the channel is done by 93. The power gain that is lost due to the
applying enough voltage across the gate- emitter bias resistor can be recovered
source terminal. What do you call this by
voltage? Ans. shunting a by-pass capacitor
Ans. pinch-off voltage 94. When a capacitor is involved at the
81. In an n-channel enhancement type MOSFET, output circuit of a transistor amplifier
the gate voltage should be ______ with it would mean
respect to the source in order to Ans. a different dc and ac load line
produce or enhance a channel. 95. How does the emitter by-pass capacitor
Ans. positive affect the dc load line?
82. To deplete a channel from a p-channel Ans. it does not affect the dc load line
IGFET depletion type, the gate voltage 96. In analyzing the quiescent currents and
should be ______ with respect to the voltages, on what load line do you
source terminal. refer?
Ans. positive Ans. dc load line
83. A junction field effect transistor has a 97. The position of the Q-point along the
drain saturation current of 10 mA and a load line is greatly affected by what
pinch-off voltage of -4 V. Calculate the component?
maximum transconductance. Ans. base-resistor
Ans. 5.0 mS 98. What will happen to the position of the
84. An n-channel MOSFET depletion type has a Q-point if the resistance base-resistor
drain saturation current IDSS = 10 mA is increased?
and a pinch-off voltage of -4 V. Ans. it moves downward
Calculate the maximum transconductance
of the transistor.
 99. For a fixed-biased transistor circuit, 111. Which class of amplifiers that have the
what will happen to the Q-point when the highest efficiency?
operation temperature rises? Ans. class D
Ans. it moves upward 112. Transistorized class C power amplifiers
100. For a battery operated transistor will usually have an efficiency of
circuit, where is a good position of the Ans. 33%
Q-point in order to minimize battery 113. For pulse-amplification, class D
consumption? amplifier is mostly used. How efficient
Ans. near cutoff region is a class D amplifier?
101. When troubleshooting a typical Ans. its efficiency reaches over 90%
transistor amplifier in the active 114. The Q-point of a class D amplifier can
region, VCE is usually _____ the supply be set or positioned at what region in
voltage VCC. the load line?
Ans. about 25% to 75% of Ans. any of these
102. Calculate the stability factor due to 115. What do you call an amplifier that is
the variation of ICBO from 1 nA to 21 nA biased to class C but modulates over the
when the temperature changes from room same portion of the curve as if it were
temperature to 100 ˚C. The change in biased to class B?
collector-current due to the change of Ans. class BC
ICBO was found to be 0.5 µA. 116. Two class B amplifiers connected such
Ans. 25 that one amplifies the positive cycle and
103. The higher the stability factor means, a the other amplifies the remaining
transistor circuit that is more sensitive negative cycle. Both output signals are
to temperature then coupled by a transformer to the
Ans. variations, and therefore undesired load.
104. What stability factor that gives the Ans. transformer-coupled push-pull
highest value for a typical voltage- amplifier
divider bias transistor circuit? 117. A push-pull amplifier that uses npn and
Ans. S (ICO) pnp transistors to amplify the positive
105. Calculate the change in the collector and negative cycles respectively.
current due to the change in ICO for a Ans. complementary-symmetry amplifier
transistor circuit at 100 ˚C. ICO at 118. A push-pull amplifier that uses either
room temperature is given to be 0.1 nA npn or pnp as its final stage. The
and increases to 20 nA at 100 ˚C. The circuit configuration looks like the
circuit has a stability factor S(ICO) = complementary-symmetry.
25. Ans. quasi-complementary push-pull
Ans. 0.5 µA amplifier
106. For most common-emitter configuration 119. Distortion that is due to the inability
with different methods of biasing, what of an amplifier to amplify equally well
is the maximum stability factor due to all the frequencies present at the input
the change of the reverse saturation signal/
current ICO? Ans. amplitude distortion
Ans. β + 1 120. Calculate the second harmonic distortion
107. What is the approximate output impedance for an output signal having a fundamental
of a common-emitter fixed-bias amplitude of 3 V and a second harmonic
configuration? The collector resistance amplitude of 0.3 V.
RC is the only load resistance/ Ans. 10 %
Ans. RC 121. An amplifier has the following percent
108. A FET is biased with a voltage-divider harmonic distortions: D2 = 10%, D3 = 5%
configuration and is set at the active and D4 = 1%. What is the amplifier %THD?
region. Ideally, what is the gate Ans. 11.22%
current? 122. T-equivalent circuit for transistor is
Ans. 0 mA considered as a _____ representation/
109. What type of FET that can be biased with Ans. physical
both negative and positive gate-source
voltage VGS? 123. What transistor model that uses a
Ans. MOSFET depletion type parameter value that is directly derived
110. How do you classify an amplifier used to from the operating condition?
amplify either amplitude modulated (AM) Ans. re or dynamic model
or frequency modulated (FM) signals? 124. The transistor model that is best suited
Ans. class S 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