InterviewSolution
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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
Transistor amplifier circuit with a feed back circuit is calledA. oscillatorB. detectorC. modulatorD. all |
| Answer» Correct Answer - A | |
| 52. |
When `n-p-n` transistor is used as an amplifier :A. Electrons move from emitter to collectorB. Holes move from emitter to baseC. Electrons move from collector to baseD. Holes move from base to collector |
| Answer» Correct Answer - A | |
| 53. |
In a transistorA. length of emitter is greater than that of collectorB. length of collector is greater than that of emitterC. both emitter and collector have same lengthD. any one of emitter and collector can have greater length |
| Answer» Correct Answer - B | |
| 54. |
Which property makes the crystalline solids to have sharp melting point ?A. Equal strength of all the interatomic bondsB. anisotropicC. long range orderD. short range order |
| Answer» Correct Answer - A | |
| 55. |
An oscillator is an amplifier withA. A large gainB. Negative oscillatorC. Positive feedbackD. No feedback |
| Answer» Correct Answer - C | |
| 56. |
A `CE` transistor amplifies weak current signal because collector current is.A. `beta` times `I_(b)`B. `beta` times `I_(C)`C. `alpha` times `I_(b)`D. `alpha` times `I_(C)` |
| Answer» Correct Answer - A | |
| 57. |
If a change of `100 mu A` in the base current of an `n-p-n` transistor in `CE` causes a change of `10 mA` in the collector current, the `ac` current gain of the transistor isA. `10`B. `100`C. `1000`D. `10000` |
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Answer» Correct Answer - B `beta=(Delta I_(c))/(Delta I_(b))`. |
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| 58. |
`npn` transistors are preferred to `pnp` transistors because they haveA. low costB. low dissipation energyC. capable of handling large powerD. electrons have high mobility than holes and hence high mobility of energy. |
| Answer» Correct Answer - D | |
| 59. |
In a `p-n` junction the depletion region is `400 nm` wide and electric field of `5 xx 10^(5) Vm^(-1)` exists in it. The minimum energy of a conduction electron, which can diffuse from n-side to the p-side is.A. `4 eV`B. `5 eV`C. `0.4 eV`D. `0.2 eV` |
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Answer» Correct Answer - D `W = Vq = Edq` `= 5 xx 10^(5) xx 400 xx 10^(-9) xx 1.6 xx 10^(-19) J` `= (5 xx 10^(5) xx 400 xx 10^(-9) xx 1.6 xx 10^(-19)J)/(1.6 xx 10^(-19))eV` `= 2000 X 10^(-4) eV = 0.2 eV`. |
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| 60. |
Pure `Si` at `300 K` has equal electron `(n_(i))` concentrations of `1.5 xx 10^(16) m^(-3)`. Doping by indium increases `n_(h) = 4.5 xx 10^(22) m^(-3). N_(e)` in the doped `Si` isA. `5 xx 10^(9)`B. `7 xx 10^(9)`C. `9 xx 10^(9)`D. `8 xx 10^(9)` |
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Answer» Correct Answer - A We know that ofr a doped semiconductor in thermal equilibrium, we have `n_(e)n_(h)=n_(i)^(2)` As per given data, `n_(i?) =1.5 xx 10^(16) m^(-3)` `n_(h) = 4.5 xx10^(22) m^(-3)` Thus `n_(e)=(n_(i)^(2))/(n_(h)) =((1.5 xx10^(16))^(2)m^(-6))/(4.5 xx10^(22)m^(-3))=5.0 xx10^(9) m^(-3)`. |
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| 61. |
An n-type and p-type silicon can be obtained by doping pure silicon with.A. Arsenic and phosphrousB. Indium and aluminiumC. Phosphorous and indiumD. aluminium and boron |
| Answer» Correct Answer - C | |
| 62. |
In a n-type semiconductor, the femi energy level liesA. in the forbidden energy gap nearer to the conduction band.B. in the forbidden energy gap nearer to the valence band.C. in the middle of forbidden energy gapD. outside the forbidden energy gap |
| Answer» Correct Answer - A | |
| 63. |
A `p-n-p` transistor is said to be in active region of operation, WhenA. Both emitter junction and collector junction are forward biasedB. Both emitter junction and collector junction are reverse biasedC. Emitter junction is forward biased and collector junction is rerverse biasedD. Emitter junction is reverse biased and collector junction is forward biased. |
| Answer» Correct Answer - C | |
| 64. |
An electric field is applied across a semiconductor. Let `n` be the number of charge carries. As temperature increases, `n` willA. increaseB. decreaseC. does not changeD. may increase or decrease |
| Answer» Correct Answer - A | |
| 65. |
In a transistor the base is made very than and is lightly doped with an impurity, because.A. to enable the collector to collect about `95 %` of the holes or electrons coming from the emitter sideB. to enable the emitter to emit small number of holes or electronsC. to save the transistors from high current effectsD. to enable the base to collect about `95 %` of holes or electrons coming from the emitter side. |
| Answer» Correct Answer - A | |
| 66. |
`p-n` junction diode can be used asA. amplifierB. detectorC. oscillatorD. capacitor |
| Answer» Correct Answer - B | |
| 67. |
Select the correct statement from the following :A. A diode can be used as a rectifierB. A triode cannot be used as a rectifierC. The currect in a diode is always proportional to the applied voltageD. The linear portion of the `I-V` characteristic of a triode is used for amplification without distortion. |
| Answer» Correct Answer - A | |
| 68. |
A junction diode is connected to a `10 V` source and `10^(3) Omega` rheostat. The slope of load line on the characteristic curve of diode by `("in" A//V)`.A. `10^(-1)`B. `10^(-2)`C. `10^(-3)`D. `10^(-4)` |
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Answer» Correct Answer - C Slope `= (Delta I)/(Delta V)`. |
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| 69. |
In a p- n junction diode not connected to any circuit,A. the potential is the same everywhereB. then p-type side is at a higher potential than the n-type side.C. there is an electric field at the junction directed from the n-type side to the p-type side.D. there is an electric field at the junction directed from the p-type side to then n-type side. |
| Answer» Correct Answer - C | |
| 70. |
In a junction transistor the emitter, base and collector are made of.A. extrinsic semi conductorsB. intrinsic semi conductorsC. both 1 and 2D. metal |
| Answer» Correct Answer - A | |
| 71. |
The tuned collector oscillator circuit used in the local oscillator of a ratio receiver makes use of a tuned circuit with `L = 60 mu H` and `C = 400 pE`. Calculate the frequency of oscillations.A. `1.03 KHz`B. `1.03 Hz`C. `1.03 GHz`D. `1.03 MHz` |
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Answer» Correct Answer - D `v=(1)/(2 pi sqrt(LC))`. |
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| 72. |
In a common base circuit, if the collector base voltage is changed by `0.6 V`, collector current changes by `0.02mA`. The output resistance will beA. `10^(4) Omega`B. `2 xx 10^(4) Omega`C. `3 xx 10^(4) Omega`D. `4 xx 10^(4) Omega` |
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Answer» Correct Answer - C `V_(CB) = I_(C) xx R_(out)`. |
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| 73. |
Two amplifiers are connected one after the other in series (cascaded). The first amplifier has a voltage gain of 10 and the second has a voltage gain of 20 . If the input signal is 0.01 V , calcualte the output AC signal . |
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Answer» When the amplifiers are Connected in series. The net voltage gain is equal to the product of the gains of the individual amplifiers. `:. Av = Av^(1) xx Av^(11)`, hear `Av^(1) = 10` , and `Av^(11) = 20` also `Av = (V_("output"))/(V_("input"))` `:.` we can write `(V_("output"))/(V_("input")) = Av^(1) xx av^(11) : V_(i n) = 0.01 V` `V_(out) = V_(i n) xx Av^(1) xx Av^(11) = 0.01 xx 10 xx 20 = 2V`. |
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| 74. |
In a transistor, the emitter circuit resistance is `100 Omega` and the collector resistance is `100 Omega`. The power gain. If the emitter and collector currents are as sumed ton be equal, will be. |
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Answer» If `I_(C) ~~ I_(B) rArr beta ~~ 1` `:. A_(P) =beta^(2)((R_(L))/(R_(i)))=((R_(L))/(R_(i))) =(100 xx 10^(3))/(100) = 1000`. |
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| 75. |
For a transistor the value of `alpha` is `0.9`. `beta` value isA. `9`B. `0.9`C. `0.09`D. `90` |
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Answer» Correct Answer - C `beta = (alpha)/(1 - alpha)`. |
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| 76. |
For a transistor `beta = 40` and `I_(B) = 25 muA`. Find the value of `I_(E)`.A. 1mAB. `1.025 mA`C. 2 mAD. `1.2 mA` |
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Answer» Correct Answer - B `beta =(I_(C))/(I_(B))rArr I_(C) =beta I_(B) = 40 xx 25 xx 10^(-6) and I_(E)=I_(B) +I_(C)`. |
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| 77. |
The input and output resistances in a common base amplifier circuits are `400 Omega` and `400 K Omega` respectively. The emitter current is `2mA` and current gain is `0.98`. Voltage gain of transistor isA. `960`B. `970`C. `980`D. `990` |
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Answer» Correct Answer - C `A_(v)=alpha(R_(0))/(R_(1))=0.98 xx(400 xx10^(3))/(400)=980`. |
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| 78. |
The `alpha` and `beta` of a transistor are alwaysA. `alpha gt 1, beta lt 1`B. `alpha lt 1, beta gt 1`C. `alpha = beta`D. `alpha beta = 1` |
| Answer» Correct Answer - B | |
| 79. |
For a common emitter amplifier, current gain is `70`. If the emitter current is `8.4 mA`, then the base current isA. `0.236 mA`B. `0.118mA`C. `0.59mA`D. `8.3 mA` |
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Answer» Correct Answer - B `beta =(I_(c))/(I_(b)) and I_(e)=I_(b)+I_(c)`. |
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| 80. |
When a transistor amplifier having current gain of `75` is given an input signal, `V_(I) = 2 sin (157 t + pi//2)`, the output signal is found to be `V_(o) = 200 sin(157 t + 3pi//2)`. The transistor is connected as :A. A common collector amplifierB. A common base amplifierC. A common emitter amplifierD. An oscillator |
| Answer» Correct Answer - C | |
| 81. |
A common emitter transistor amplifier has a current gain of `50`. If the load resistance is `4k Omega`, and input resistance is `500 Omega`, the voltage gain of amplifier is.A. 100B. 200C. 300D. 400 |
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Answer» Correct Answer - D `A_(V) = beta (R_(L))/(R_(i))`. |
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| 82. |
In case of `NPN` transistor, emitter current is always greater than collector current, because :A. Collector side is revese biased and emitter side is forward biasedB. Collector being reverse biased attracts more electronsC. Some electrons are lost in baseD. Collector side is forward biased and emitter side is reverse biased. |
| Answer» Correct Answer - C | |
| 83. |
A working transitor with its three legs marked `P, Q and R` is tested using a multimeter No conduction is found between `P, Q `by connecting the common (negative) terminal of the multimeter to `R`and the other (positive) terminal to or `Q` some resistance is seen on the multimeter . Which of the following is true for the transistor ?A. It is a `pnp` transistor with `R` as emitterB. It is an `npn` transistor with `R` as collectorC. It is an `npn` transistor with `R` as baseD. It is `pnp` transistor with `R` as collector. |
| Answer» Correct Answer - C | |
| 84. |
When a positive voltage signal is applied to the base of a common emitter `npn` amplifierA. The emitter current decreasesB. The collector voltage becomes more positiveC. The collector voltage becomes less positiveD. The collector current decreases |
| Answer» Correct Answer - C | |
| 85. |
In case of common emitter `p-n-p` transistor input characteristic is a graph drawn.A. With `I_(C)` on y-axis and `V_(CE)` on x-axis keeping `I_(B)` constantB. With `I_(B)` on y-axis and `V_(BE)` on x-axis keeping `V_(CE)` constantC. With `I_(C)` on y-axis and `I_(B)` on x-axis keeping `V_(CE)` constantD. With `V_(BE)` on y-axis and `V_(CE)` x- axis keeping `I_(B)` constant. |
| Answer» Correct Answer - B | |
| 86. |
An electrically neutral semiconductor hasA. equal amounts of negative and positive chargeB. no minority charge carriesC. no majority charge carriersD. no free charges |
| Answer» Correct Answer - A | |
| 87. |
The conduction band and valency band of a good conductors areA. well separatedB. just touchC. very closeD. overlap |
| Answer» Correct Answer - D | |
| 88. |
If the ratio of the concentration of electron to that of holes in a semiconductor is `(7)/(5)` and the ratio of current is `(7)/(4)` then what is the ratio of their drift velocities ?A. `5//8`B. `4//8`C. `5//4`D. `4//7` |
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Answer» Correct Answer - C `I=n eAv_(d)` `(I_(e))/(I_(h))=(n_(e)xx(v_(d))_(e))/(n_(h)xx(v_(d))_(h))` Here `(n_(e))/(n_(h)) = (7)/(5), (I_(e))/(I_(h)) = (7)/(4)` `:. (7)/(4) =(7)/(5)xx((v_(d))_(e))/((v_(d))_(h))` `rArr ((v_(d))_(e))/((v_(d))_(h))=(5)/(7)xx(7)/(4)=(5)/(4)`. |
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| 89. |
There is no hole current in conductors because they haveA. high conductivityB. high electron densityC. no valence bandD. overlapping of valence and conduction bands. |
| Answer» Correct Answer - D | |
| 90. |
The `I-V` characteristic of an `LED` is.A. B. C. D. |
| Answer» Correct Answer - D | |
| 91. |
n-type semiconductor isA. negativity chargedB. positively chargedC. neutralD. may be positive or negative |
| Answer» Correct Answer - C | |
| 92. |
When the conductivity of a semiconductor is only due to breaking of covalent bonds, the semi conductor is called.A. n-typeB. p-typeC. intrinsicD. extrinsic |
| Answer» Correct Answer - C | |
| 93. |
The level formed due to impurity atom, in the for hidden energy gap, very near to the valence band in a p-type semiconductor is calledA. acceptor levelB. donar levelC. conduction levelD. forbidden level |
| Answer» Correct Answer - A | |
| 94. |
A semiconductor is known to have an electron concentration of `5 xx 10^(13)//cm^(3)` and hole concentration of `8 xx 10^(12)//cm^(3)`. The semiconductor isA. n-typeB. p-typeC. intrinsicD. insulator |
| Answer» Correct Answer - A | |
| 95. |
In the insulatorsA. the valence band is partially filled with electronsB. the conduction band is partiallt filled with electronsC. the conduction band is partially filled with electrons and valence band is emptyD. the conduction band is empty and the valence band is filled with electrons. |
| Answer» Correct Answer - D | |
| 96. |
p-type semiconductor isA. negativity chargedB. positively chargedC. neutralD. may be positive or negative |
| Answer» Correct Answer - C | |
| 97. |
If the lattice constant of this semiconductor is decreased, then which of the following is correct ? .A. All `E_(c),E_(g) & E_(v)` decreaseB. All `E_(c),E_(g) & E_(v)` increaseC. `E_(c)` and `E_(v)` increase, but `E_(g)` decreaseD. `E_(c)` and `E_(v)` decrease but `E_(g)` increase |
| Answer» Correct Answer - D | |
| 98. |
The bond in semiconductors isA. covalentB. ionicC. metallicD. hydrogen |
| Answer» Correct Answer - A | |
| 99. |
Among the following, the wrong statement on the case of semiconductor isA. Resistivity is in between that of a conductor and insulatorB. Temperature coefficient of resistance is negativeC. Doping increases conductivityD. At absolute zero temperature it behaves like a conductor. |
| Answer» Correct Answer - D | |
| 100. |
In semiconductors the for bidden energy gap between `V.B` and `C.B` is of the order ofA. 1 eVB. 5 eVC. 1 KeVD. 1 MeV |
| Answer» Correct Answer - A | |