Banking Physics Semiconducting Devices Question Bank

done Semiconductor Electronics Total Questions - 53

• question_answer1)
  In a p-n junction
  A)
   the potential of p & n sides becomes higher alternately done clear
  B)
   the p side is at higher electrical potential than n side   done clear
  C)
   the n side is at higher electric potential than p side done clear
  D)
   both p & n sides are at same potential done clear
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• question_answer2)
  Barrier potential of a p-n junction diode does not depend on
  A)
   doping density               done clear
  B)
   diode design   done clear
  C)
   temperature         done clear
  D)
          forward bias done clear
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• question_answer3)
  The energy band gap is maximum in
  A)
   metals              done clear
  B)
   super conductors done clear
  C)
   insulators            done clear
  D)
          semiconductors done clear
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• question_answer4)
  The part of a transistor which is most heavily doped to produce large number of majority carriers is
  A)
   emmiter   done clear
  B)
   base done clear
  C)
   collector done clear
  D)
   can be any of the above three done clear
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• question_answer5)
  When n-p-n transistor is used as an amplifier
  A)
   electrons move from collector to base done clear
  B)
   holes move from emitter to base done clear
  C)
   electrons move from base to collector done clear
  D)
   holes move from base to emitter   done clear
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• question_answer6)
  In a common base amplifier the phase difference between the input signal voltage and the output voltage is
  A)
   0                                   done clear
  B)
   \[\pi /4\] done clear
  C)
   \[\pi /2\]                 done clear
  D)
          \[\pi \] done clear
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• question_answer7)
  Inverter converts
  A)
   alternating current into direct current done clear
  B)
   direct current into alternating current   done clear
  C)
   current at low voltage to current at high voltage done clear
  D)
   None of these done clear
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• question_answer8)
  The Donor level in a semiconductor is placed
  A)
   half-way in the forbidden energy gap done clear
  B)
   in the forbidden energy gap close to the upper edge of the valence band done clear
  C)
   in the conduction band close to the lower edge to the conduction band done clear
  D)
   in the forbidden energy gap close to the lower edge of the conduction band   done clear
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• question_answer9)
  If the distance between the conduction band and valence band is 1 eV. This combination is
  A)
   semiconductor                 done clear
  B)
   conductor done clear
  C)
   metal              done clear
  D)
          insulator done clear
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• question_answer10)
  Carbon, silicon and germanium have four valence electrons each. These are characterised by valence and conduction bands separated by energy band gap respectively equal to \[{{({{E}_{g}})}_{c}},{{({{E}_{g}})}_{si}}\] and \[{{({{E}_{g}})}_{Ge}}\]. Which of the following statements is true?
  A)
   \[{{({{E}_{g}})}_{Si}}<{{({{E}_{g}})}_{Ge}}<{{({{E}_{g}})}_{C}}\] done clear
  B)
   \[{{({{E}_{g}})}_{C}}<{{({{E}_{g}})}_{Ge}}<{{({{E}_{g}})}_{Si}}\] done clear
  C)
   \[{{({{E}_{g}})}_{C}}>{{({{E}_{g}})}_{Si}}>{{({{E}_{g}})}_{Ge}}\]   done clear
  D)
   \[{{({{E}_{g}})}_{C}}={{({{E}_{g}})}_{Si}}={{({{E}_{g}})}_{Ge}}\] done clear
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• question_answer11)
   In an unbiased p-n junction, holes diffuse from the p-region to n-region because
  A)
   free electrons in the n-region attract them. done clear
  B)
   they move across the junction by the potential difference. done clear
  C)
   hole concentration in p-region is more as compared to p-region.   done clear
  D)
   all the above done clear
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• question_answer12)
  For a transistor amplifier, the voltage gain
  A)
   remains constant for all frequencies. done clear
  B)
   is high at high and low frequencies and constant in the middle frequency range. done clear
  C)
   is low at high and low frequencies and constant at mid frequencies.   done clear
  D)
   none of the above done clear
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• question_answer13)
  p-n junction diode works as a insulator, if connected
  A)
   to A.C.                         done clear
  B)
   in forward bias done clear
  C)
   in reverse bias        done clear
  D)
         None of these done clear
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• question_answer14)
  In an n-type silicon, which of the following statement is true?
  A)
   Electrons are majority carriers and trivalent atoms are the dopants. done clear
  B)
   Electrons are minority carriers and pentavalent atoms are the dopants. done clear
  C)
   Holes are minority carriers and pentavalent atoms are the dopants.   done clear
  D)
   Holes are majority carriers and trivalent atoms are the dopants. done clear
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• question_answer15)
  Which of the statements is true for p-type semiconductors??
  A)
   Electrons are majority carriers and trivalent atoms are the dopants. done clear
  B)
   Electrons are minority carriers and pentavalent atoms are the dopants. done clear
  C)
   Holes are minority carriers and pentavalent atoms are the dopants. done clear
  D)
   Holes are majority carriers and trivalent atoms are the dopants.   done clear
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• question_answer16)
  When a forward bias is applied to a p-n junction, it
  A)
   raises the potential barrier. done clear
  B)
   reduces the majority carrier current to zero. done clear
  C)
   lowers the potential barrier.   done clear
  D)
   None of these done clear
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• question_answer17)
  The potential barrier, in the depletion layer, is due to
  A)
   ions                    done clear
  B)
   holes done clear
  C)
   electrons            done clear
  D)
          both [b] and [c] done clear
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• question_answer18)
  Zener diode is used as
  A)
   half wave rectifier                       done clear
  B)
   full wave rectifier done clear
  C)
   A.C. voltage stabilizer   done clear
  D)
   D.C. voltage stabilizer done clear
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• question_answer19)
  For a transistor amplifier, the voltage gain
  A)
   remains constant for all frequencies done clear
  B)
   is high at high and low frequencies and constant in the middle frequency range done clear
  C)
   is low at high and low frequencies and constant at mid frequencies   done clear
  D)
   None of these done clear
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• question_answer20)
   In a semiconductor, the concentration of electrons is \[8\times {{10}^{14}}/c{{m}^{3}}\]and that of the holes is \[5\times {{10}^{12}}/c{{m}^{3}}\]. The semiconductor is
  A)
   p-type              done clear
  B)
   n-type   done clear
  C)
   intrinsic             done clear
  D)
          Cannot say done clear
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• question_answer21)
  When a semiconductor is heated, its resistance
  A)
   decreases                        done clear
  B)
   increases done clear
  C)
   remains unchanged        done clear
  D)
   either [b] or [c] done clear
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• question_answer22)
  The forbidden gap in the energy bands of germanium at room temperature is about
  A)
   1.1 eV                          done clear
  B)
   0.1 eV done clear
  C)
   0.67 eV               done clear
  D)
          6.7 eV done clear
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• question_answer23)
  To obtain a p-type germanium semiconductor, it must be doped with
  A)
   arsenic             done clear
  B)
   antimony done clear
  C)
   indium               done clear
  D)
   phosphorus done clear
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• question_answer24)
  Which impurity is doped in Si to form n-type semiconductors?
  A)
   Al                                done clear
  B)
   B done clear
  C)
   As                                  done clear
  D)
   None of these done clear
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• question_answer25)
  In extrinsic semiconductors
  A)
   the conduction band and valence band overlap done clear
  B)
   the gap between conduction band and valence band is more than 16eV done clear
  C)
   the gap between conduction band and valence band is near about 1 eV   done clear
  D)
   the gap between conduction band and valence band will be 100 eV and more done clear
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• question_answer26)
  Function of rectifier is
  A)
   to convert A. C. into D.C.   done clear
  B)
   to convert D.C. into A.C. done clear
  C)
   Both [a] and [b] done clear
  D)
   None of these done clear
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• question_answer27)
  Zener breakdown takes place if
  A)
   doped impurity is low done clear
  B)
   doped impurity is high   done clear
  C)
   less impurity in n-part done clear
  D)
   less impurity in p-part done clear
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• question_answer28)
  Which one of the following is not a correct statement about semiconductors?
  A)
   The electrons and holes have different mobilities in a semiconductor done clear
  B)
   In an n-type semiconductor, the Fermi level lies closer to the conduction band edge done clear
  C)
   Silicon is a direct band gap semiconductor   done clear
  D)
   Silicon is has diamond structure done clear
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• question_answer29)
  The energy band gap is minimum in
  A)
   metals                            done clear
  B)
   superconductors done clear
  C)
   insulators                      done clear
  D)
   semiconductors. done clear
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• question_answer30)
  An oscillator is nothing but an amplifer with
  A)
   positive feedback             done clear
  B)
   negative feedback done clear
  C)
   large gain                      done clear
  D)
   no feedback done clear
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• question_answer31)
  When a solid with a band gap has a donor level just below its empty energy band, the solid is
  A)
   an insulator done clear
  B)
   a conductor done clear
  C)
   p-type semiconductor done clear
  D)
   n-type semiconductor   done clear
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• question_answer32)
  Regarding a semiconductor which one of the following is wrong?
  A)
   There are no free electrons at room temperature   done clear
  B)
   There are no free electrons at OK done clear
  C)
   The number of free electrons increases with rise of temperature done clear
  D)
   The charge carriers are electrons and holes done clear
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• question_answer33)
   p-n junction is said to be forward biased, when
  A)
   the positive pole of the battery is joined to the p-semiconductor and negative pole to the n-semiconductor   done clear
  B)
   the positive pole of the battery is joined to the n-semiconductor and p-semiconductor done clear
  C)
   the positive pole of the battery is connected to n- semiconductor and/?- semiconductor done clear
  D)
   a mechanical force is applied in the forward direction done clear
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• question_answer34)
  At absolute zero, Si acts as
  A)
   non-metal                     done clear
  B)
   metal done clear
  C)
   insulator                         done clear
  D)
   None of these done clear
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• question_answer35)
  When n-type semiconductor is heated
  A)
   number of electrons increases while that of holes decreases done clear
  B)
   number of holes increases while that of electrons decreases done clear
  C)
   number of electrons and holes remain same done clear
  D)
   number of electrons and holes increases equally   done clear
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• question_answer36)
  To use a transistor as an amplifier
  A)
   The emitter base junction is forward biased and the base collector junction is reverse biased   done clear
  B)
   no bias voltage is required done clear
  C)
   both junctions are forward biased done clear
  D)
   both junctions are reverse biased done clear
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• question_answer37)
  The part of the transistor which is heavily doped to produce large number of majority carriers is
  A)
   emitter   done clear
  B)
   base done clear
  C)
   collector done clear
  D)
   any of the above depending upon the nature of transistor done clear
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• question_answer38)
  When a p-n junction diode is reverse biased the flow of current across the junction is mainly due to
  A)
   diffusion of charges done clear
  B)
   drift of charges   done clear
  C)
   depends on the nature of material done clear
  D)
   both drift and diffusion of charges done clear
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• question_answer39)
  When an n-p-n transistor is used as an amplifier then
  A)
   electrons flow from emitter to collector   done clear
  B)
   holes flow from emitter to collector done clear
  C)
   electrons flow from collector to emitter done clear
  D)
   electrons flow from battery to emitter done clear
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• question_answer40)
  An n-p-n transistor conducts when
  A)
   both collector and emitter are negative with respect to the base done clear
  B)
   both collector and emitter are positive with respect to the base done clear
  C)
   collector is positive and emitter is negative with respect to the base   done clear
  D)
   collector is positive and emitter is at same potential as the base done clear
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• question_answer41)
  Reverse bias applied to a junction diode
  A)
   increases the minority carrier current done clear
  B)
   lowers the potential barrier done clear
  C)
   raises the potential barrier   done clear
  D)
   increases the majority carrier current done clear
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• question_answer42)
  In semiconductors, at room temperature
  A)
   the conduction band is completely empty done clear
  B)
   the valence band is partially empty and the conduction band is partially filled done clear
  C)
   the valence band is completely filled and the conduction band is partially filled   done clear
  D)
   the valence band is completely filled done clear
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• question_answer43)
  Application of a forward bias to a p-n junction
  A)
   widens the depletion zone. done clear
  B)
   increases the potential difference across the depletion zone. done clear
  C)
   increases the number of donors on the n side.   done clear
  D)
   increases the electric field in the depletion zone. done clear
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• question_answer44)
  A piece of copper and another of germanium are cooled from room temperature to 80 K. The resistance of
  A)
   each of them increases done clear
  B)
   each of them decreases done clear
  C)
   copper increases and germanium decreases done clear
  D)
   copper decreases and germanium increases   done clear
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• question_answer45)
  In an intrinsic semiconductor
  A)
   only electrons are responsible for flow of current done clear
  B)
   both holes and electrons carry current   done clear
  C)
   both holes and electrons carry current with electrons being majority carriers done clear
  D)
   only holes are responsible for flow of current done clear
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• question_answer46)
  If the conductivity of a semiconductor is only due to break up of the covalent bonds due to thermal excitation, then the semiconductor is called
  A)
   intrinsic                           done clear
  B)
   extrinsic done clear
  C)
   donor                           done clear
  D)
   acceptor done clear
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• question_answer47)
  The mobility of conduction electrons is greater than that of holes, since electrons
  A)
   are lighter done clear
  B)
   are negatively charged done clear
  C)
   require smaller energy for moving through crystal lattice   done clear
  D)
   undergo smaller number of collisions done clear
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• question_answer48)
  In the symbol of a transistor , the arrow head points in the direction of flow of
  A)
   holes                              done clear
  B)
   electrons done clear
  C)
   majority carriers             done clear
  D)
   minority carriers done clear
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• question_answer49)
  Transistors are essentially
  A)
   power driven devices done clear
  B)
   current driven devices   done clear
  C)
   voltage driven devices done clear
  D)
   resistance driven devices done clear
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• question_answer50)
  In a transistor
  A)
   emitter is more highly doped than collector   done clear
  B)
   collector is more highly doped than emitter done clear
  C)
   both are equally doped done clear
  D)
   None of the above done clear
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• question_answer51)
  One way in which the operation of an n-p-n transistor differs from that of zip-n-p
  A)
   the emitter junction is reverse biased in n-p-n. done clear
  B)
   the emitter junction injects minority carriers into base region of the p-n-p done clear
  C)
   the emitter injects holes into the base of the p-n-p and electrons into the base region n-p-n   done clear
  D)
   the emitter injects holes into the base of n-p-n done clear
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• question_answer52)
  n-p-n transistors are preferred to p-n-p transistors because:
  A)
   they have low cost done clear
  B)
   they have low dissipation energy done clear
  C)
   they are capable of handling large power done clear
  D)
   electrons have high mobility than holes and hence high mobility of energy   done clear
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• question_answer53)
  An alternating current can be converted into direct current by a
  A)
   rectifier                           done clear
  B)
   transformer done clear
  C)
   dynamo                        done clear
  D)
   motor done clear
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