Semiconductors and Transistors - Electronics Engineering test questions

Semiconductors and Transistors - Electronics Engineering test questions

(1) ________________ is an active device

(A) Silicon controlled rectifier
(B) Transformer
(C) Loud speaker
(D) Bulb

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(2) 1.12ev is the forbidden energy gap of

(A) Germanium
(B) Gallium
(C) Silicon
(D) Aluminium

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(3) Three valence electrons are not present in

(A) Boron
(B) Gallium
(C) Aluminium
(D) Phosphorous

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(4) When the temperature is absolute zero, a semiconductor behaves like

(A) A resistor
(B) An insulator
(C) A conductor
(D) A variable resistor

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(5) The process of merging a free electrons and holes is called

(A) Mixing
(B) Neutralization
(C) Recombination
(D) Zeroing

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(6) If a voltage is applied to an intrinsic semiconductor at room temperature

(A) Electrons will move to positive terminal and holes will move to negative terminal
(B) Electrons will move to negative terminal and holes will move to positive terminal
(C) Maximum number of electrons and holes will move to negative terminal
(D) Nothing will happen

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(7) The semiconductor material is ____________ before doping

(A) Heated
(B) Purified
(C) Washed
(D) Dehydrated

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(8) Forbidden energy gap for silicon is 1.12ev and for germanium is 0.72ev. Therefore, it can be concluded that

(A) Conductivity of both will be same at 100 degree Celsius.
(B) Conductivity of both will be same at less than 100 degree Celsius
(B) At room temperature silicon conductivity will be more than that of germanium.
(C) At room temperature silicon conductivity will be less than that of germanium

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(9) In PN junction, the region that contains uncompensated acceptor and donor ions is called

(A) Active region
(B) Passive region
(C) Depletion region
(D) Transition region

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(10) When forward bias is applied to a junction diode

(A) Potential barrier is decreased
(B) Potential barrier is increased
(C) Majority and minority carrier current is reduced to zero
(D) Nothing will happen

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(11) The current in reverse bias for a PN junction diode may be

(A) Between 0.5 A and 1 A
(B) Few micro amperes or few nano amperes
(C) Few amperes
(D) More than 1 A

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(12) ____________ rectifier needs 4 diodes

(A) Bridge rectifier
(B) Half wave rectifier
(C) Center-tap full wave rectifier
(D) None of the above

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(13) A voltage at 50 Hz is supplied to a full wave bridge rectifier .The lowest ripple factor will be

(A) 200 Hz
(B) 50 Hz
(C) 100 Hz
(D) 400 Hz

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(14) The PIV rating for signal diodes is usually in the range of

(A) 150V to 400V
(B) 10V to 30V
(C) 1V to 10V
(D) 30V to 150V

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(15) _________ are generally power diodes

(A) Germanium diodes
(B) Silicon diodes
(C) Both germanium and silicon diodes
(D) Either germanium or silicon diodes

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(16) Resistivity of a semiconductor mainly depends on

(A) Atomic nature of semiconductor
(B) Shape of semiconductor
(C) Size of semiconductor
(D) Other parameters of semiconductor

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(17) For incident light, the photo electric current (in amperes per watt) depends on

(A) Intensity of incident light
(B) Frequency of incident light
(C) Both frequency and intensity of incident light
(D) None of the above

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(18) The valence electrons of any semiconductor material are

(A) 3 or 5
(B) 8
(C) 6
(D) 4

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(19) ___________ causes diffusion current in a diode

(A) Crystal formation
(B) Chemical energy
(C) Heat energy
(D) Electricity

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(20) Hall’s effect can be used to measure

(A) Electrostatic field intensity
(B) Average number of holes or electrons
(C) Magnetic field intensity
(D) Concentration of carriers

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(21) When a strong electric field is applied across a PN junction, covalent bonds break apart

(A) It is called low voltage breakdown
(B) It is called reverse breakdown
(C) It is called avalance breakdown
(D) It is called lever breakdown

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(22) When the temperature of a N-P junction is increased, what will increase??

(A) Reverse leakage current
(B) Width of depletion layer
(C) Junction barrier voltage
(D) All of the above

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(23) Failure of a transistor may be caused by

(A) Short circuit due to overloads
(B) Open weld at the wire leads to semiconductor
(C) Overheating due to circuit failure
(D) Any of the above

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(24) In most transistors, physically the collector region is made larger than the emitter region

(A) To distinguish it from base region and emitter region
(B) To dissipate heat properly
(C) As collector region is sensitive to ultra-violet rays
(D) To reduce resistance in the path of flow of electrons

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(25) Usually encapsulation of the transistor is done in

(A) Epoxy resin
(B) Graphite powder
(C) Enamel paint
(D) None of the above

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(26) Number specification that refers to FET with one gate is

(A) 2Y
(B) 3X
(C) 3N
(D) 3Y

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(27) Heat in the heat sink is disposed off mainly by

(A) Conduction
(B) Radiation
(C) Natural convection
(D) Forced convection

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(28) The amplifier circuit using junction transistors has the best gain in

(A) Common collector
(B) Common base
(C) Common emitter
(D) All of the above has same gain

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(29) Class of amplifiers that operates with least distortion is

(A) Class A
(B) Class B
(C) Class C
(D) Class D

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(30) To improve the low frequency response of an RC-coupled amplifier

(A) More bias is used
(B) Higher Cc is used
(C) Lower RL is provided
(D) Less gain is provided

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(31) Plot to show the input volt-ampere characteristics of a common-emitter configuration is

(A) Vce versus Ic for constant values of Ib
(B) Vcb versus Ic for constant values of Ie
(C) Vbe versus Ib for constant values of Vce
(D) None of the above

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(32) ________________ circuits can operate class AB for audio power output

(A) Darlington pair
(B) Cascade
(C) Emitter follower
(D) Push pull

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(33) The overall gain of three cascade stages having gains of 10,20 and 25 will be

(A) 55
(B) 500
(C) 10
(D) 5000

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(34) The fastest switching device is

(A) Triode
(B) MOSFET
(C) JFET
(D) BJT

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(35) In IC’s, the cascaded amplifier which is often used is

(A) Direct coupled
(B) Inductively coupled
(C) Transformer coupled
(D) Capacitively coupled

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(36) Which one of the following is expected to have highest operating frequency?

(A) MOSFET
(B) JFET
(C) Bipolar transistor
(D) All of the above

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(37) For FET, which of the statement given below is not true?

(A) It has large (gain x bandwidth)
(B) It has high input impedance
(C) It is less noisy than bipolar transistor
(D) All of the above

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(38) The minimum interference with frequency response is present in

(A) Impedance coupling
(B) Direct coupling
(C) Transformer coupling
(D) RC coupling

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(39) Two stages that are present in Darlington pair are

(A) Both CC
(B) Both CE
(C) CE and CC
(D) CE and CB

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(40) Dependence of the emitter bias is mainly on

(A) Ie
(B) Gain
(C) Signal input
(D) None of the above.

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For questions 41 and 42 refer to given data below:

In a half wave rectifier, the turns ratio of a transformer is 10:1 and the primary is connected to the power mains, 220V, 50Hz.

(41) If resistance of the diode in forward bias is zero then the dc voltage across the load will be nearly

(A) 10V
(B) 8V
(C) 12V
(D) 15V

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(42) The diodes peak inverse voltage will be nearly

(A) 50V
(B) 62V
(C) 31V
(D) 41V

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(43) When a small amount of antimony is added to germanium then

(A) Concentration of antimony on the edges of the crystal will be more
(B) Resistance will increase
(C) Concentration of free electrons will be more than holes in the semiconductor
(D) P-type semiconductor is formed

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(44) In case of a NPN transistor, if collector junction is reversed biased and emitter junction is forward biased then the transistor will operate in

(A) Inverted region
(B) Active region
(C) Saturation region
(D) Cut-off region

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For questions 45 and 46 refer to given data below:

Collector leakage current is 5 micro amps and alpha dc is 0.98 for a certain transistor

(45) If Ie = 1mA, the collector current will be

(A) 0.985mA
(B) 1.005mA
(C) 0.955mA
(D) 0.975mA

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