Semiconductors

1. Single-element semiconductors are characterized by atoms with ____ valence electrons.A.3B.4C.5D.2E.none of the above

2. Under normal conditions a diode conducts current when it isA.reverse-biased. B.forward-biased.C.avalanched. D.saturated.

3. A diode conducts when it is forward-biased, and the anode is connected to the ________ through a limiting resistor.A.positive supplyB.negative supplyC.cathodeD.anode

4. As the forward current through a silicon diode increases, the internal resistanceA.increases.B.decreases.C.remains the same.

 

5. For a forward-biased diode, the barrier potential ________ as temperature increases.A.decreasesB.remains constantC.increases

 

6. An n-type semiconductor materialA.is intrinsic.B.has trivalent impurity atoms added.C.has pentavalent impurity atoms added.D.requires no doping.

7. For a forward-biased diode, as temperature is ________, the forward current ________ for a given value of forward voltage.A.decreased, increasesB.increased, increasesC.increased, decreasesD.decreased, decreases

08. Which statement best describes an insulator?A.

A material with many free electrons.

B.A material doped to have some free electrons.C.

A material with few free electrons.

D.

No description fits.

09. You have an unknown type of diode in a circuit. You measure the voltage across it and find it to be 0.3 V. The diode might beA.

a silicon diode.

B.a germanium diode.C.a forward-biased silicon diode.D.

a reverse-biased germanium diode.

10. What types of impurity atoms are added to increase the number of conduction-band electrons in intrinsic silicon?A.

bivalent

B.octavalentC.

pentavalent

D.

trivalent

E.none of the above

11. What factor(s) do(es) the barrier potential of a pn junction depend on?A.

type of semiconductive material

B.the amount of dopingC.the temperatureD.

all of the above

E. type of semiconductive material and the amount of doping but not the temperature

12. Reverse breakdown is a condition in which a diodeA.

is subjected to a large reverse voltage.

B.is reverse-biased and there is a small leakage current.C.has no current flowing at all.D.

is heated up by large amounts of current in the forward direction.

13. What occurs when a conduction-band electron loses energy and falls back into a hole in the valence band?A.

doping B.recombination

C.generation D.[NIL]

Diode Applications

14. Each diode in a center-tapped full-wave rectifier is ________ -biased and conducts for ________ of the input cycle.

A.

forward, 90º

B.reverse, 180ºC.

forward, 180º

D.

reverse, 90º

15. The output frequency of a full-wave rectifier is ________ the input frequency.A.

one-half

B.equal toC.

twice

D.

one-quarter

16. PIV is which of the following?A.

peak input voltage

B.peak inverse voltageC.peak immediate voltageD.

positive input voltage

17. If the ac supply is 50 Hz, what will be the ripple frequency out of the full-wave rectifier?A.

50 Hz

B.60 HzC.

100 Hz

D.

120 Hz

18. A silicon diode in a half-wave rectifier has a barrier potential of 0.7 V. This has the effect ofA.

reducing the peak output voltage by 0.7 V.

B.increasing the peak output voltage by 0.7 V.C.reducing the peak input voltage by 0.7 V.D no effect.

.

19. If the ac supply is 60 Hz, what will be the ripple frequency out of the half-wave rectifier?A.

30 Hz

B.50 HzC.

60 Hz

D.

120 Hz

20. In the operation of a half-wave rectifier with a capacitor-input filter, the ripple factor can be lowered by ________ the value of the filter capacitor or ________ the load resistors.A.

decreasing, decreasing

B.decreasing, increasingC.increasing, decreasingD.

increasing, increasing

Bjt DEVICES21. How much is the base-to-emitter voltage of a transistor in the "on" state?

A.

0 V

B.0.7 VC.0.7 mVD.

Undefined

22. For what kind of amplifications can the active region of the common-emitter configuration be used?A.

Voltage

B.CurrentC.PowerD.

All of the above

23. In the active region, while the collector-base junction is ________-biased, the base-emitter is ________-biased.A.

forward, forward

B.forward, reverseC.

reverse, forward

D.

reverse, reverse

24. What range of resistor values would you get when checking a transistor for forward- and reverse-biased conditions by an ohmmeter?A.

100 to a few k , exceeding 100 k

B.Exceeding 100 k , 100 to a few kC.Exceeding 100 k , exceeding 100 kD.

100 to a few k , 100 to a few k

25. In which region are both the collector-base and base-emitter junctions forward-biased?A.

Active

B.CutoffC.

Saturation

D.

All of the above

26. What does a reading of a large or small resistance in forward- and reverse-biased conditions indicate when checking a transistor using an ohmmeter?A.

Faulty device

B.Good deviceC.Bad ohmmeterD.

None of the above

27. Determine the value of when = 100.

A 1.01

.B.101C.

0.99

D.

Cannot be solved with the information provided

28.  dc = ________A.

IB / IE

B.IC / IE

C.

IC / IB

D.

None of the above

29. How many carriers participate in the injection process of a unipolar device?A.

1 B.2

C.0 D.3

30. What are the ranges of the ac input and output resistance for a common-base configuration?A.

10 –100 , 50 k –1 M

B.50 k –1 M , 10 –100 C.10 –100 k , 50 –1 kD.

None of the above

31. What is the most frequently encountered transistor configuration?A.

Common-base B.Common-collector

C.

Common-emitter D.Emitter-collector

Field-Effect Transistors32. For a JFET, the value of VDS at which ID becomes essentially constant is the

A pinch-off voltage.

.B.cutoff voltage.C.breakdown voltage.D.

ohmic voltage.

33. The ________ has a physical channel between the drain and source.A.

D-MOSFET B.E-MOSFET

C.V-MOSFET D.[NIL]

34. What type(s) of gate-to-source voltage(s) can a depletion MOSFET (D-MOSFET) operate with?A.

zero

B.positiveC.negativeD.

any of the above

35. Midpoint bias for a D-MOSFET is ID = ________, obtained by setting VGS = 0.A.

IDSS / 2

B.IDSS / 3.4C.

IDSS

36. On the drain characteristic curve of a JFET for VGS = 0, the pinch-off voltage isA.

below the ohmic area.

B.between the ohmic area and the constant current area.C.between the constant current area and the breakdown region.D.

above the breakdown region.

37. Which of the following devices has the highest input resistance?A.

diode

B.JFETC.

MOSFET

D.

bipolar junction transistor

38. The value of VGS that makes ID approximately zero is theA.

pinch-off voltage.

B.cutoff voltage.C.breakdown voltage.D.

ohmic voltage.

39. A dual-gated MOSFET isA.

a depletion MOSFET.

B.an enhancement MOSFET.C.a VMOSFET.D.

either a depletion or an enhancement MOSFET.

40. What three areas are the drain characteristics of a JFET (VGS = 0) divided into?A.

ohmic, constant-current, breakdown

B.pinch-off, constant-current, avalancheC.ohmic, constant-voltage, breakdown

41. The resistance of a JFET biased in the ohmic region is controlled byA.

VD. B.VGS.

C.VS. D.VDS.

42. High input resistance for a JFET is due toA.

a metal oxide layer.

B.a large input resistor to the device.C.an intrinsic layer.D.

the gate-source junction being reverse-biased.

43. For a JFET, the change in drain current for a given change in gate-to-source voltage, with the drain-to-source voltage constant, isA.

breakdown.

B.reverse transconductance.C.

forward transconductance.

D.

self-biasing.

Semiconductor Diodes

44. What does a high resistance reading in both forward- and reverse-bias directions indicate?A.

A good diode

B.An open diodeC.A shorted diodeD.

A defective ohmmeter

45. Which capacitance dominates in the reverse-bias region?A.

depletion

B.conversionC.40 DiffusionD.

140 None of the above

46. What is the state of an ideal diode in the region of nonconduction?

A.

An open circuit

B.A short circuitC.UnpredictableD.

Undefined

47. What unit is used to represent the level of a diode forward current IF?A pA

.B.nAC. AD.

mA

48. The diffused impurities with ________ valence electrons are called donor atoms.A.

4 B.3

C.

5 D.0

49. What is the range of the operating voltage level for LEDs?A.

5–12 mV

B.1.7–3.3 VC.5–12 VD.

20–25 V

50. At what kind of operating frequency diffusion or transition is a capacitor represented in parallel with the ideal diode?A.

Low frequency

B.Moderate frequencyC.Mid frequencyD.

Very high frequency

51. What is the resistor value of an ideal diode in the region of conduction?A.

0

B.5 kC.UndefinedD.

Infinity

52. Which of the following elements is most frequently used for doping pure Ge or Si?A Boron

.B.GalliumC.IndiumD.

All of the above

53. What is the maximum power rating for LEDs?A.

150 mW

B.500 mWC.1 WD.

10 W

54. What is the value of the transition capacitance for a silicon diode when VD = 0? (Choose the best answer.)A.

1 pF

B.3 pFC.5 pFD.

10 pF

55. Which of the following ratings is true?

A.

Si diodes have higher PIV and narrower temperature ranges than Ge diodes.

B.Si diodes have higher PIV and wider temperature ranges than Ge diodes.C.Si diodes have lower PIV and narrower temperature ranges than Ge diodes.D.

Si diodes have lower PIV and wider temperature ranges than Ge diodes.

56. Which capacitance dominates in the forward-bias region?A.

Diffusion

B.TransitionC.DepletionD.

None of the above

57. In what state is a silicon diode if the voltage drop across it is about 0.7 V?A.

No bias

B.Forward biasC.Reverse biasD.

Zener region

Bipolar Junction Transistors

58. A transistor amplifier has a voltage gain of 100. If the input voltage is 75 mV, the output voltage is:A.

1.33 V

B.7.5 VC.13.3 VD.

15 V

59. What is the ratio of IC to IB?A. DC

B.hFE

C. DC

D. either DC or hFE, but not DC

60. For normal operation of a pnp BJT, the base must be ________ with respect to the emitter and ________ with respect to the collector.A.

positive, negative

B.positive, positiveC.

negative, positive

D.

negative, negative

61. When a transistor is used as a switch, it is stable in which two distinct regions?A.

saturation and active

B.active and cutoffC saturation and cutoff

.D.

none of the above

62. For a silicon transistor, when a base-emitter junction is forward-biased, it has a nominal voltage drop ofA.

0.7 V.

B.0.3 V.C.0.2 V.D.

VCC.

63. The value of DC

A.

is fixed for any particular transistor.

B.varies with temperature.C.varies with IC.D.

varies with temperature and IC.

64. What is the order of doping, from heavily to lightly doped, for each region?A.

base, collector, emitter

B.emitter, collector, baseC.emitter, base, collectorD.

collector, emitter, base

65. In what range of voltages is the transistor in the linear region of its operation?

A.

0 < VCE

B.0.7 < VCE < VCE(max)

C.VCE(max) > VCE

D.

none of the above

66. The magnitude of dark current in a phototransistor usually falls in what range?A.

mA B.μA

C nA D.pA

.

67. The dc load line on a family of collector characteristic curves of a transistor shows theA.

saturation region.

B.cutoff region.C.active region.D.

all of the above

FET Devices

69. What is the level of IG in an FET?A.

Zero amperes

B.Equal to ID

C.Depends on VDS

D.

Undefined

70. What is the range of an FET's input impedance?A.

10 to 1 k

B.1 k to 10 kC.50 k to 100 kD.

1 M to several hundred M

71. Which of the following controls the level of ID?A.

VGS B.VDS

C.IG D.VDG

72. It is the insulating layer of ________ in the MOSFET construction that accounts for the very

desirable high input impedance of the device.A.

SiO B.GaAs

C.

SiO2 D.HCl

73. The BJT is a ________ device. The FET is a ________ device.A.

bipolar, bipolar

B.bipolar, unipolarC.unipolar, bipolarD.

unipolar, unipolar

74. The transfer curve is not defined by Shockley's equation for the ________.

A.

JFET

B.depletion-type MOSFETC.

enhancement-type MOSFET

D.

BJT

75. The region to the left of the pinch-off locus is referred to as the ________ region.A.

saturation

B.cutoffC.

ohmic

D.

All of the above

76. A BJT is a ________-controlled device. The JFET is a ________ - controlled device.A.

voltage, voltage

B.voltage, currentC.

current, voltage

D.

current, current

77. Which of the following FETs has the lowest input impedance?A.

JFET

B.MOSFET depletion-typeC.MOSFET enhancement-type

D.

None of the above

78. Which of the following applies to MOSFETs?A.

No direct electrical connection between the gate terminal and the channel

B.Desirable high input impedanceC.Uses metal for the gate, drain, and source connectionsD.

All of the above

79. At which of the following is the level of VDS equal to the pinch-off voltage?A.

When ID becomes equal to IDSS

B.When VGS is zero voltsC.IG is zeroD.

All of the above

80. Which of the following input impedances is not valid for a JFET?A.

1010

B.109 C.

108

D.

1011

Special-Purpose Diodes81. Schottky diodes are also known as

A.

PIN diodes.

B.hot carrier diodes.C.step-recovery diodes.D.

tunnel diodes.

82. Zener diodes with breakdown voltages less than 5 V operate predominantly in what type of

breakdown?A.

avalanche B.zener

C.varactor D.Schottky

83. The Schottky diode is usedA.

in high-power circuits.

B.in circuits requiring negative resistance.C.

in very fast-switching circuits.

D.

in power supply rectifiers.

84. You have an application for a diode to be used in a tuning circuit. A type of diode to use might beA.

an LED.

B.a Schottky diode.C.a Gunn diode.D.

a varactor.

85. What kind of diode is formed by joining a doped semiconductor region with a metal?A.

laser B.tunnel

C.pin D.Schottky

86. Which diode employs graded doping?A.

zener B.LED

C.tunnel D.step-recovery

87. LEDs are made out ofA.

silicon.

B.germanium.C Gallium Arsenide.

.D.

silicon and germanium, but not gallium.

88. The normal operating region for a zener diode is theA.

forward-bias region.

B.reverse-bias region.C.zero-crossing region.D.

reverse-breakdown region.

89. The process of emitting photons from a semiconductive material is calledA.

photoluminescence.

B.gallium arsenide.C.

electroluminescence.

D.

gallium phosphide.

90. What type of diode maintains a constant current?A.

LED

B.zenerC.

current regulator

D.

pin

E.none of the above

91. Back-to-back varactor diodes are used for what reason?A.

over-voltage protection

B.a wider tuning rangeC.

to eliminate harmonic distortion

D.

no reason; only zeners are used in a back-to-back configuration

92. A tunnel diode is usedA.

in high-power circuits.

B.in circuits requiring negative resistance.C.in very fast-switching circuits.D.

in power supply rectifiers.

93. A laser diode normally emitsA.

coherent light.

B.monochromatic light.C.

coherent and monochromatic light.

D.

neither coherent nor monochromatic light.

Thyristors94. The ________ can be externally programmed to turn on at a desired anode-to-gate voltage

level.A.

UJT B.PUT

C.SCR D.SCS

95. The silicon-controlled switch (SCS) is similar in construction to theA.

triac.

B.diac.C.

SCR.

D.

4-layer diode.

96. The ________ can conduct current in either direction and is turned on when a breakover

voltage is exceeded.A.

SCR B.diac

C.SCS D.triac

97. You need to design a relaxation oscillator circuit. The most likely device to use might beA.

an SCR.

B.a UJT.C.a triac.D.

a 4-layer diode.

98. You have the schematic diagram of several types of circuits. Which of these circuits most likely uses a triac?A.

an oscillator

B.an ac motor controlC.a programmable oscillatorD.

an amplifier

99.  The SCR can be triggered on by a pulse at theA.gate.B.anode.C.cathode.D.none of the above

100. How many semiconductor layers are thyristors constructed with?A.2 B.3C.4 D.5

101. Your boss has asked you to recommend a thyristor that will enable you to turn it on with a pulse and also turn it off with a pulse. Which of the following should you recommend?A.an SCRB.an SCSC.a PUTD.a triac