Electronic Devices and Circuits

1. The drift velocity of electrons in silicon

a. Is proportional to the electric field for all values of electric field

b. is independent of the electric field

c. increases at the low values of electric field

d. increases linearly with electric field at low values of electric field and gradually saturates at higher values of electric field

2. The diffusion potential across a p-n junction

a. decreases with increasing doping concentration

b. increases with decreasing band gap

c. does not depend on doping concentrations

d. increases with increase in doping concentrations

3. A BJT is said to be operating in the saturation region if

a. both the junctions are reverse biased

b. base-emitter junction is reverse biased and base-collector junction is forward biased

c. base- emitter junction is forward biased and -collector junction is reverse biased

d. both the junctions are forward biased

4. To obtain very high input and output impedances in a feedback amplifier, the topology mostly used is

a. voltage-series

b. current series

c. voltage shunt

d. current shunt

5. In a bipolar-junction transistor the current gain increases

a. base doping is increased and base width is reduced

b. base doping is reduced and base width is increased

c. base doping and base width are reduced

d. base doping and base width are increased

6. In a BJT transistor the collector break-down voltage increases

a. base doping is increased and base width is reduced

b. emitter area is increased and collector area is reduced

c. both a and b

d. none of these

7. In JFET a pinch-off voltage decreases

a. channel doping is reduced

b. conductivity of channel increased

c. channel length is reduced

d. gate area is reduced

8. In JFET transconductance increases

a. conductivity of channel increased

b. channel length is reduced

c. channel length is increased

d. gate area is reduced

9. In an extrinsic semiconductor resistivity decreases

a length of the semiconductor is reduced

b. length of the semiconductor is reduced

c. doping concentration is increased

d. band gap is high

10. photoconductivity is low

a. band gap is high

b . length of the semiconductor is reduced

c. area of cross-section of the semiconductor is increased

d. length of the semiconductor is increased

11. A common collector amplifier

a. provides voltage gain but no current gain

b. provides current gain but no voltage gain

c. provides neither voltage gain nor power gain

d. provides neither current nor voltage gain

12. If a transistor is operating with both of its junctions forward biased, but with the collector base forward bias greater than the emitter base forward bias, then it is operating in the

a. forward active node

b. reverse saturation mode

c. reverse active mode

d. forward saturation mode

13. In a bipolar transistor at room temperature, if emitter is doubled, then voltage across its base-emitter junction

a. doubles

b. halves

c. increases by about 20mV

d. decreases by about 20 mV

14. In a common emitter BJT amplifier, the maximum usable supply voltage is limited by

a. avalanche breakdown of base-emitter junction

b. collector base breakdown voltage with emitter open

c. collector-emitter breakdown voltage with base open

d. zener breakdown voltage of the emitter base junction

15. The dissipation at the collector is zero in the quiescent state and increases with excitation in the case of a

a. Class A series-fed amplifier

b. class A transistor coupled amplifier

c. Class AB amplifier

d. Class B amplifier

16. In a transistor amplifier the reverse saturation current Ico

a. doubles for every 10° C rise in temperature

b. doubles for every 1° C rise in temperature

c. doubles for every 5° C rise in temperature

d. none of these

17. Avalanche photodiodes are preferred over PIN diodes in optical communication system because of

a. speed of operation

b. higher sensitivity

c. larger bandwidth

d. larger power handling capacity

18. The transition region in an open circuited pn junction contains

a. free electrons only

b. holes only

c. both free electrons and holes

d. uncovered immobile impurity ions

19. In a pn diode, hole diffuse from p-region to n-region because

a. there is higher concentration of holes in the p-region

b. holes are positively charged

c. holes are urged to move by the barrier potential

d. free-electron in the n-region attract the holes

20. In a pn diode , with increase of reverse bias the reverse currenr

a. increases

b. decreases

c. remain constant

d. may increase or decrease depending on the doping

21. The reverse saturation current Io in germanium diodes varies as

a. T

b. T 2

c. T 1.5

d. 1/T

22. In an npn diffused junction transistor, the p-type base region is formed on the n-type collector region through process of

a. alloying

b. epitaxial

c. change in the nature of doping during crystal growth

d. diffusion of p-type impurity

23. In a pnp transistor operating in the active region: in the base region , the main stream of current is

a. drift of holes

b. diffusion of holes

c. drift of electrons

d. diffusion of electrons

24. In inverted operation of a transistor

a. both junctions are reverse biased

b. both junctions are forward biased

c. emitter junction is reverse biased while collector junction is forward biased

d. emitter junction is forward biased while collector junction is reverse biased

25. Most of the small signal transistors are

a. npn silicon transistor in plastic package

b. pnp silicon transistor in plastic package

c. npn germanium transistor in metallic case

d. pnp germanium transistor in metallic case

26. In an npn transistor operating in the active region, the main current crossing the collector junction from base side is

a. hole drift current

b. hole diffusion current

c. electron diffusion current

d. electron drift current

27. A transistor with emitter junction forward biased and collector junction reverse biased is said to operate in

a. active region

b. saturation region

c. cutoff region

d. inverted region

28. In a transistor, current ICBO

a. increase with increase of temperature

b. decrease with increase of temperature

c. is normally greater for Si transistor than Ge transistor

d. mainly depends on the emitter base junction bias

29. In a transistor current ICBO flow in

a. base and emitter leads

b. collector and emitter leads

c. base and collector leads

d. emitter, base and collector leads

30. Use of buried layer in npn monolithic transistor causes the series resistor to

a. increase

b. decrease

c. remain constant

d. become temperature sensitive

31. In comparison with conventional npn IC transistor, the current gain of lateral pnp IC transistor is

A. excessively higher

b. higher

c. lower

d. of the same order

32. An IC comprises of 40 logic gates, each of which consists of 5 components. This forms a case of

a. SSI

b. MSI

c. LSI

d. VLSI

33. A single IC chip contains more than 120 logic gates. This forms a case of

a. SSI

b. MSI

c. LSI

d. VLSI

34. The photoetching process consists in

a. removal of photoresist

b. cerbing lines on the wafer before dicing

c. diffusing impurities

d. removal of SiO2 layer from selected portions

35. Reliability of IC’s may be increased by

a. reducing component size

b. additional testing

c. reducing the number of interconnections

d. operation at higher voltage

36. Diffusion constant D of phosphorous impurity silicon

a. remains temperature invariant

b. continuously decreases with increase of temperature

c. continuously decreases with increase of temperature

d. none of these

37. Microwave IC’s

a. can be made using thin film on ceramics

b. can be made using thick film on ceramics

c. are very difficult to fabricate

d. are not fabricated so far

38. A diffused resistor in an IC

a. is formed along with fabrication of transistors

b. can be fabricated with precision for any resistance value

c. is fabricated before transistor diffusion

d. is fabricated after transistor diffusion

39. Photomasking process in IC fabrication

a. is used to remove selected regions of SIO2

b. controls the depth of diffusion

c. forms an insulation layer which prevents diffusion in selected areas

d. consists in removal of photoresist

40. Microwave IC’s

a. have inferior performance

b. are not possible to fabricate

c. always use discrete components

d. are initially being made as hybrid type on ceramic substrates

41. Small size and weight of IC’s

a. is a disadvantage in circuit operation

b. increase the fabrication operation

c. reduces the reliability

d. make them specially useful in missiles

42. Monolithic IC design is based on

a. extensive use of transistors and missiles

b. extensive use of RC coupling

c. using high value resistors and capacitors

d. making the area of circuit elements as large as possible

43. The most important reason for use of IC arrays is

a. high reliability

b. reduced power consumption

c. simplified circuit design

d. simplified processing

44. IC’s are economical for use in logic systems because

a. of the quantity of repeat circuits used

b. binary circuits are possible only with IC’s

c. diffusion process is simpler

d. private circuit boards are inexpensive

45. In processing IC slices

a. SiO2 is removed in final

b. isolation structure is completed first

c. slices are never oxidized

d. separate diffusions are used for each component

46. In IC’s diodes

a. need a separate diffusion process

b. are formed simultaneously with other elements

c. are double ended

d. are formed on the top of the SiO2 surface of the wafer

47. Solid state diffusion

a. is an important process in fabrication of IC’s

b. can be carried out at low temperature

c./ cannot be used to form pn junction

d. result in impurities moving rapidly into silicon wafer

48. The most important factor governing the cost of IC components is

a. shape of the component

b. area occupied by the component

c. number of electrode connections

d. location of the component on the slice

49. In silicon monolithic IC, isolation

a. is not necessary because silicon substrate is an insulator

b. is needed because silicon is electrically conducting

c. can be obtained by scribing

d. can be obtained by use of SiO2 layer

50. IC’s are probe tested

a. to measure individual components

b. after separation into individual wafers

c. on the complete slice for dc operation

d. to check small signal a.c characteristics

51. An important merit of monolithic IC’s for linear applications is that

a. a wider frequency range is possible

b. all components are at the same temperature

c. bias stabilization can be achieved with close tolerance resistors

d. high value capacitors can be economically fabricated

52. Extemely low power dissipation and low cost per gate can be achieved in which of the following IC?

a. ECL

b. CMOS

c. TTL

d. MOS

53. Which of following digital IC family can give maximum fan out?

a. ECL

b. PMOS

c. CMOS

d. HTL

54. In monolithic IC’s resistore are formed

a. from manganin wire

b. from ceramic material

c. by using solid diffusion of impurity

d. from aluminium

55. The term midium scale integration refers to

a. having a single level of metalization

b. technology with complexity in the range of 10 to 100 gates

c. with complexity below 10 gates

d. manufactured on medium volume production line

56. In IC electronic system

a. cost of printed circuit is negligible

b. it is not economical to use types with the optimum complexity so as to get the low cost per gate

c. total system is same irrespective of type used

d. it is desirable to use simple gate types mounted as printed circuit board

57. As complexity of a packaged IC’s is increased

a. cost per gate goes on decreasing

b. package cost per gate remains the same

c. overall cost per gate reduces, reaches a minimum at some level of complexity and then increases

d. overall cost always increases with the increase oof complexity

58. Large Scale Integration

a. does not require costly process facilities

b. can not be applied to MOS systems

c. refers only to integrated electronic components fabricated on full slices of silicon

d. refers to technology used to fabricate IC’s with complexity above 100 gates

59. Very Large scale Integration

a. does not require costly process facilities

b. can not be applied to MOS systems

c. refers only to integrated electronic components

fabricated on full slices of silicon

d. refers to technology used to fabricate IC’s with complexity below 100 gates

60. When a chip with more than two gates is assembled into an IC package, then

a. system reliability is worst

b. system becomes castlier

c. total cost remains unaltered

d. none of these

61. In temperature control syatem, IC’s

a. Need have low gainb. B. are used instead of thermocouplec. Compare the output of a thermocoupls with a reference and amplify the difference

signal

d. are used as the main power control element

62. In industrial electronic control

a. a.c power systems are always used

b. IC’s can be uesd with advantage in feed back control circuits

c. we are simply concentrated in establishing stable

d. use of IC’s is not of consequences

63. MOS IC’s are fast gaining popularity because

a. their density of packing is more and power consumption is less

b. they occupy less space and hence are cheaper

c. they use direct coupled transistor logic

d. their propagation delay is less

64. IC video amplifiers

a. can not be converted to narrow band amplifiers

b. are always relatively narrow band amplifiers

c. amplify only at very high frequencies

d. giveuniform amplification from dc upto typically 40 MHz

65. A typical medium gain IC Op Amp

a. is suitable for use at low frequencies only

b. has only one input terminal

c. has an open loop gain of about 100

c. has an open loop gain of about 2500

66. An IC sense amplifier

a. consists of a linear amplifier, a voltage level detector, and a logic pulse forming circuit

c. is a memory system

d. consists of four separate linear amplifiers

67. The most popularly used logic IC’ are

a. ECL and CTL

b. RTL and RCTL

c. TTL and DTL

d. simple gate types

68. A dual 4 input gate IC consists of

a. a single gate with eight inputs

b. four gates each with two inputs

c. two separate gates with four inputs

d. a simple gate with two groups of four inputs

69. CMOS has which of the folowing advantage over PMOS/NMOS?

a. Simpler fabrication process

b. lower Pd

c. Low input capacitance

d. greater suitabilit

70. TTL has which of the following advantage over CMOS?

a. lower Pd

b. use of transistors alone as circuit elements

c. greater suitability for LSI

d.. Simpler fabrication process

71. In a multiphase IC, isolation is obtained by

a. silicon doioxide

b. back-to-back diodes

c. undoped silicon

d. doped silicon region having high resistance

72. IC’s use silicon primarily because

a. silicon is available in abundance

b. of its higher forbidden energy gap

c. of properties of silicon dioxide

d. of its high mechanical strength

73. In order to form a structure containing both pnp and npn transisrors monolithic IC requires

a. four layers

b. three layersc.

c. Five layers

d. six layers

74. Transistors in monolithic IC’s

a. are made as separate wafers

b. use isolation junction as the collector junction

c. are similar to discrete planar transistors but have the collector cantacts on the top surface

d. are identical with discrete planar transistor

75. The ON- resistance rd of an FET is the ratio

a. V DS/ID at the origin

b. V DS/ID in the saturation region

c. ∆V DS/∆ID in the saturation regiond. VGS/ID at the origin

77. In a JFET, beyond the pinch off voltage as drain voltage increases the drain current

a. remains almost constant

b. decreases

c. increases

d. may increase or decrease

78. When gate to source voltage VGS of a p-channel JFET is made positive, the drain current

a. increases

b. decreases

c. remains constant

d. may increase or decrease

79. The main drawback of a JFET is its

a. high input impedance

b. low input impedance

c. higher noise

d. lower gain

80. In a JFET, the amplification factor µ, transconductance gm , and the dynamic drain resistance rd are related as

a. µ,= gm/r d

b. µ =rm/gm

c. µ=gm . rd

d. m= gm . rd

81. Out of the four devices mentioned below , the fastest switching device is

a. JFET

b. BJT

c. MOSFET

d. Triode

82. JFET can operate in

a. depletion mode only

b. enhancement mode only

c. either depletion or enhancement mode at a time

c. both depletion and enhancement modes simultaneously

83. Which of the following device has the highest input impedance?

a. CE BJT

b. CC BJT

c. JFET

d. MOSFET

84. A field-effect transistor(FET)

a. has three pn junction

b. uses a forward biased junction

c. depends on the variation of a magnetic field for its operation

d. depends on the variation of a reverse votage its operation

85. The operation of JFET involves

a. flow of minority carriers alone

b. flow of majority carriers only

c. flow both minority and majority carriers

d. use of a magnetic field

86. A pnpn diode is a

a. negative resistance device

b. voltage controllable device

c. controlled rectifier

d. current controlled negative resistance device

87. The pnpn diode

a. is unilateral device

b. bilateral device

c. may function either as unilateral or as bilateral device

d. functions as a bilateral device depending on the ambient temp

88. In a pnpn diode, breakover takes place when

a. (α1+ α2) = 0.5

b. (α1+ α2) = 0.9

c. (α1+ α2) = 1.0

d. α1= α2

89. An SCS is a

a. pnpn diode with three terminals

b. pnpn diode with one gate

c. pnpn diode with two gates

d. pnpn diode made of germanium

90. Triac is a

a. 2 terminal bidirectional switch

b. 3 terminal bidirectional switch

c. 2 terminal unilateral switch

d. 3. Terminal unilateral switch

91. Diac is a

a. 2 terminal bidirectional switch

b. 2 terminal unilateral switch

c. 3 terminal bidirectional switch

d. 3. Terminal unilateral switch

92. Diac is a silicon device with

a. 3 layers and one gate

b. 3 layers and no gate

3. 4 layers and one gate

4. 4 layers and no gate

93. Thermistor is used for measurement of power at

a. audio frequencies

b. high frequencies

c. very high frequencies

d. microwave frequencies

94. Photoconductive cell most popularly used for visible light spectrum uses

a. Ge

b. Si

c. Ga As

d. cadmium sulphide

95. In a photodiode light is focused to fall on

a. p region only

b. n-region only

c. full p and n regions

d. junction region only

96. Response time of PIN photodiode is of the order of

a. 0.1 ns

b. 1 ns

c. 10ns ns

d. 1 ms

97. In phototransistor, light is focused to fall on

a. emitter to base junction

b. collector to base junction

d. base region only

d. all the three regions of the transistor

98. Photovoltic emf of a Ge photovoltaic cell is of the order of

a. 0.1 volt

2. 0.5 volt

c. 1.1 volt

d. 1.72 volt

99. Photovoltic emf of a Si photovoltaic cell is of the order of

a. 0.1 volt

2. 0.5 volt

c. 1.1 volt

d. 1.72 volt

100. LED gives off visib;le light from

a. region of depletion layer

b. p region alone

c. n region alone

d. both p and n regions