Practice Test


1) Which one of the following is not the advantage of semi conductor device over tubes ?


2) P-N junction can be used as :


3) To provide the abundance of holes the impurity added should be :


4) For forward biasing P-N junction the positive terminal of the battery is connected to :


5) The number of functions in a transistor is :


6) The number of terminals in a transistor is :


7) To produce N-type crystal Ge or Si may be doped with a substance that is :


8) Transistor was invented by :


9) In n-p-n transistor, P-type crystal is :


10) The base of a transistor serves a similar function as :


11) A p-type semiconductor can be obtained by adding :


12) The current gain for common base configuration is 0.95. What is the current gain in common emitter configuration ?


13) Frequency of an oscillator is given by :


14) In the binary system the number 100 represents :


15) The binary number corresponding to the decimal number 49 is :


16) OR gate operation means :


17) In AND operation if Y is output and A and B are inputs the truth table is :


18) In NOT operation if Y is output and A is input, then :


19) Under space charge limited conditions the plate current in a diode is 10mA at plate potential of 100 V. If the plate potential is changed to 400V, what is the plate current ?


20) A triode valve has an amplification factor 20 and its plate potential is 300 V. What should be the grid potential to reduce the plate current zero ?


21) Diode value can be used as :


22) In a p-n-p transistor operating as amplifier with common emitter configurations a change in base current from 100mA to 200mA produces a change in collector current from 10mA to 18mA. Calculate the current grain of transistor :


23) The pure semiconductor has :


24) The type of bonding in Ge crystal is :


25) The conductivity of P-type semiconductor is due to :


26) N-type Ge is obtained on doping the Ge crystal with :


27) A P-type crystal is obtained by doping :
(A) silicon with arsenic
(B) silicon with aluminium
(C) Ge with boron
(D) Ge with phosphorus.


28) Majority current carries in N-Types are :


29) The number of valency electrons in a good conductor is generally :


30) The electrons are forbidden in a brand in a crystal called the :


31) The behaviour of Ge as a semiconductor is due to the width of :


32) When triode is used as an amplifier, the phase difference between the input signal voltage and the output is :


33) Three triodes having amplification factors of 12,18,36 and with mutual conductance 3,6, 4m A/V respectively are operated in parallel. What is the equivalent mutual conductance ?


34) The current gain of common-base circuit is 0.97, what is the current gain of common-emitter circuit ?


35) In a common - base circuit of transistor, current amplification factor is 0.95. Calculate the emitter current , if base current is 0.2 mA.


36) In case of a p-n junction diode at high value of reserve bias the current raises sharply. The value of reserve bias is know as :


37) For a transistor the current amplification factor is 0.8. If the transistor is now in common - emitter configuration, the change in collector current when the base current change by 6mA is :


38) An oscillator in nothing but an amplifier with :


39) To use a transistor as an amplifier :


40) When we apply reverse bias to a junction diode it :


41) The depletion layer in the P-N junction is caused by :


42) When a P-N junction is resersed biased, the flow of current across the junction is mainly due to :


43) Digital circuits can be made to be respective use of


44) NOR gate is a combination of


45) The output of a 2 input OR gate is 0 only what its :


46) Crystals exhibit :


47) A solid having uppermost energy - band partially filled with electrons is called :


48) A transistor is preferable to a triode valve when used as amplifier because it :


49) What is the atomic radius of a BCC crystal structure?


50) The atomic packing factor for a face centered cubic cell is :


51) In a cubic unit cell of bcc structure, the lattice points or the number of atoms are :


52) The number of modules per unit cell in fcc lattice is :


53) The crystal has fcc structure and its lattice constant is 3.5 A. Its atomic radius is :


54) The ratio of atomic radius 'r' and lattice parameter 'a' of fcc system is :


55) The co - ordination number of hexagonal close packing [hcp] is :


56) Polymers are :


57) Of the various cubic systems, one having closed packing is :


58) In which of the following states of matter the atomic kinetic and potential energies are comparable ?


59) CuNi exhibits :


60) Which of the binding is weakest in strength ?


61) Which of the following is supercooled ?


62) The ionic crystals are :


63) MgO exhibits :


64) Metallic solids are always opaque because :


65) What helped in the study of the geometry of the internal structured of the crystals ?


66) Quartz is a crystalline solid because it is :


67) Silver has fcc structure. If the interatomic spacing is 2.888 A, the lattice constant is :


68) The density of a crystalline material is equal to the :


69) Which of the following properties are common to liquids and amorphous solids ?


70) What is co-ordination number ? The no. of the :


71) In a semiconductor diode, the reserve biased current is due to drift of free electrons and holes caused by :


72) Which one of the following shows correctly the input characteristics of a transistor in common base configuration ?


73) In a semiconductor crystal, if the current flows due to breakage of crystal bonds, then the semiconductor is called :


74) When two semiconductors of P and N-type are brought into contact, they form a P-N junction which acts like a :


75) In an n-P-N-P transistor circuit, the collector current is 10 mA. If 90% of the electrons emitted reach the collector :


76) On increasing the reverse bias to a large value in a P-N junction diode current :


77) When N- type of semiconductor is heated


78) How many NAND gates are used to form AND gate ?


79) what are ripples ?


80) The "FREE ELECTRON " model of metallic solid does not explain :


81) Who was first to use Boolean algebra for describing the operation of logic gates ?


82) Which gate is formed by inverting the output of AND gate ?


83) Ice is an example of :


84) In a semiconductor, it is found that three quarter of current is being carried by electrons and the quarter by holes. If at this temperature the drift velocity of electrons is two and half times of holes, the the ratio of electrons to holes present is :


85) Energy bonds in solids are a consequence of :


86) When aluminium is added as an impurity to silicon, then resulting material is :


87) In junction diode, the holes are because of :


88) In the CB mode of a transistor, when the collector voltage is changed by 0.5 volt, the collector current changes by 0.05mA. The output resistance will be :


89) Which of the following is NOT equal to O in the Boolean algebra ?


90) In the Boolean algebra which of the following is NOT equal to A ?


91) The nature of binding for a crystal with alternate and evenly spaced positive and negative ions is :


92) The energy gap between conduction band and valence band is order of 0.7 eV. It is a :


93) In bcc crystal, the distance between any two nearest atom is


94) What account for flow of charge carriers in forward and reserve biasing of silicon p-n diode ?


95) The intrinsic semiconductor behaves as an insulator at :


96) For a logic 0101 the waveform is :


97) Which of the following figure represents an ideal diode characteristics ?


98) The forward biased diode is :


99) Which of the following when added as an impurity into the silicon, produces n- type semi - conductor :


100) A current gain for a transistor working as CB amplifier is 0.96. If emitter current is 7.2 mA, then base current is :


101) In a P-N junction :


102) In Germanium crystal, impurity donor element have valency :


103) At 0 K temp., a p-type semiconductor :


104) The potential barrier in the depletion layer is due to :


105) Barrier potential of a P- N junction diode does not depend on :


106) Reverse bias applied on a junction diode :


107) Assertion : The resistivity of a semiconductor increases with temperature.
Reason : The atom of a semiconductor vibrate with larger amplitude at higher temperature thereby increasing its resistivity.


108) Assertion : In a transistor the base is made thin.
Reason : A thin base makes the transistor stable.


109) A n-p-n transistor conducts when :


110) The peak voltage in the output of a half wave diode rectifier fed with a sinusoidal signal without filter is 10V. The d.c. component of output voltage is :


111) Of the diodes shown in the following diagrams, which one is reserve biased ?


112) Copper has face centered cubic (fcc) lattice with interatomic spacing equal to 2.54 A. The value of lattice constant for this lattice is :


113) Which of the following logic gates is an universal gate ?


114) Consider an n-p-n transistor amplifier in common emitter configuration . The current gain of the transistor is 100. If the collector changes by 1 mA, what will be the change in emitter current ?


115) Application of a forward bias to a P-N junction :


116) Zener diode is used for :


117) A transistor oscillator using a resonant circuit was an inductor L and a capacitor C in series produce oscillations of frequency f. If L is double and C is changes to 4C, the frequency will be :


118) When a P-N diode is reverse biased then :


119) A light emitting diode (LED) has a voltage drop of 2 volt across it and passes a current of 10 mA when it operates with a 6 volt battery through a limiting resistor R. The value of R is :


120) The output of a diode rectifier is :


121) In intrinsic semiconductor at room temperature, number of electrons and holes are :


122) Enetordy of a superconductor is :


123) The amplification factor of a triode depends on the :


124) A pentode can be used :


125) A modulator is used for :


126) Degree of modulation :


127) The static amplification factor of a triode value depends upon :


128) The fourth electrode in a tetrode is to :


129) The input a.c current frequency to a full wave rectifier is v then the output frequency of the current is :


130) A triode value has an amplification factor of 15. There is a change in the grid voltage by 0.3 volt, then by how much should the plate voltage change as to keep the current constant ?


131) What is the minimum number of parameters required to describe a three dimension crystal system :


132) The energy gab between the valence band and the conduction band for a material is 6 eV. The material is,


133) An a.c. signal of 50 Hz frequency is input of a full wave rectifier using two diodes. The output frequency after full wave rectification is


134) In a transistor in the common emitter mode :


135) When the input of a two logic gate are 0 and 0, the output is 1. When the inputs are 1 and 0 the output is zero. The logic gate is of the type :


136) The impurity atoms with which a pure silicon should be doped to make a p-type semiconductor is :


137) At room temperature,a p-type semi conductor has :


138) The least region in a transistor is :


139) NAND gate is :


140) In an NPN transistor the collector current is 24 mA. If 80% of electrons reach collector its base current in mA is :


141) For a cubic crystal structure which one of the following relations indicating the cell characteristics is correct ?


142) A p-n photodiode is made of a material with a band gap of 2.0 eV. The minimum frequency of the radiation that can be absorbed by the material is nearly :


143) A p-n photodiode is fabricated from a semiconductor with a band gap of 2.5 eV. It can detect a signal of wavelenght.


144) Which one of the following statement is FALSE ?


145) In forward biasing of the p-n junction :


146) If a small amount of antimony is added to germanium crystal :


147) The co-ordination number for a body centred cubic cell is :


148) The lattice parameter for a crystalline structure is 3.6 A. Atomic radius in simple cubic crystal is :


149) The atomic radius for a face centred cubic cell of lattice parameter a is :


150) In a transistor :


151) Truth table of NOR gate is :


152) The space lattice of diamond is :


153) The conductivity of a semiconductor is given by


154) A hole diffuses from the P-side to the N-side in a P-N junction. This means that :


155) The number of molecules per unit cell in fcc lattice is :


156) Which of the following types of binding produces crystals that are transparent to visible light and conduct electricity only at higher temperatures ?


157) In case of diamond, the forbidden gap is about :


158) Metallic solids are always opaque because :


159) If r is the input resistance and R is the output resistance (R > r), the voltage gain in common emitter configuration is :


160) If r is the input resistance and R is the output resistance (R > r), the voltage gain in common base configuration is :


161) The ionization track of a subatomic particle can be photographed in :


162) Rubber is an example of :


163) Which of the following is not the property of a crystalline substance ?


164) The minimum proportion of available volume which may be filled by hard spheres arranged in various structures is :


165) Atoms of copper sulphate crystal are arranged in :


166) If N is Avogadro's number, M the atomic weight and d is density, the number of free electrons per unit volume of a monovalent metallic crystal can be expressed as :


167) The atomic packing factor for a fcc cell is :


168) Zener diode is used for


169) When an impurity is doped into an intrinsic semiconductor the conductivity of the semiconductor


170) A capacitor is to be used to provide smoothing for a half wave rectifier. In which of the following diagrams is capacitor correctly connected ?


171) Silicon is a semiconductor. If a small amount of As is added to it, then its electrical conductivity


172) An intrinsic - semiconductor at absolute zero of temperatures behaves as


173) To obtain P - type Si semiconductor, we need to dope pure Si with


174) If the forward voltage in a diode is increased, the width of the depletion region


175) The impurity atom that should be added to Germanium to make its n - type is


176) Statement 1 : An n-type semiconductor has a large number of electrons but still it is electrically neutral.
Statement 2 : An n-type semiconductor is obtained by doping an intrinsic semiconductor with a pentavalent impurity.


177) Statement 1 : The conductivity of a semiconductor increases with rise of temperature.
Statement 2 : On rising temperature covalent bonds of semiconductor break.


178) Of the diodes shown in figure which one is reverse biased ?


179) The dominant contribution to current comes from holes in case of


180) A PN junction diode cannot be used


181) Diffusion current in a p-n junction is grearer than the drift current in magnitude


182) For germanium crystal, the forbidden energy gap in joule is


183) The cathode of a diode valve is emitting electrons when it is heated. The valve is connected in a circuit. When the circuit is closed, what happens to the emission of electrons ?


184) In an n-type semiconductor, donor valence band is


185) A pure semiconductor has


186) When the conductivity of a semiconductor is only due to breaking of covalent bonds, the semiconductor is called


187) Reverse bias applied to a junction diode


188) The current amplification of the common base N P N transistor is 0.96. What is the current gain if it is used as common emitter amplifier ?


189) The electron energy states in a solid are shown in terms of bands ( not sharp levels, as for atoms). In a semiconductor we have electrons in conduction band, inner bands, and valence band. Now which of the following is incorrect ?


190) Statement 1 : The probability of electrons to be found in the conduction band of an intrinsic semiconductor at a finite temperature decrease exponentially with increasing band gap
Statement 2 :It will be more difficult for the electron to cross over the large band gap while going from valence band to conduction band.


191) Statement 1 : The temperature coefficient of resistance is positive for metals and negative for p-type semiconductor
Statement 2 : The effective charge carriers in metals are negatively charged whereas in p-type semiconductor, they are positively charged.


192) What will be the forward current at a forward voltage of 0.6 V ?


193) What will be the increase in the current, if the voltage across the diode is increased to 0.7 V ?


194) What is the dynamic resistance ?


195) Which of the following is not analogue signal ?


196) Refer to the circuit shown in figure. What inputs X and Y will produce a high output at R ?


197) How many NAND gates are required to make an OR gate ?


198) Statement 1 : NAND or NOR gates are called digital building blocks.
Statement 2 : The repeated use of NAND ( or NOR ) gates can produce all the basic or complicated gates


199) Statement 1 : NOT gate is also called invertor circuit.
Statement 2 : NOT gate inverts the input order.


200) The circuit above behaves as


201) If all the NOR gate in the circuits are replaced by NAND gates, the circuit would perform the logic operation of


202) The output of OR gate is 1


203) The boolean expression for NAND gate is


204) If A = 1 and B = 0, then A.A + B in the boolean expression is equal to


205) Which of the following is the logic symbol of NAND gate ?


206) If one terminal of an XOR gate is kept at 1, the output will be zero when the other terminal is at


207) In boolean algebra, which of the following is not equal to zero


208) Which of the following is not correct ?


209) Identify the gate in box II


210) Identify the gate in box III


211) An AND gate can be prepared by repetitive use of


212) The number of NAND gates required to make NOT gate is


213) Statement 1 : In a two input NAND gate if one of the inputs is kept high, it acts as an inverter.
Statement 2 : A low input produces a high output in NAND gate


214) The logic gate circuit is


215) Which one of the following cirucits would give waveforms as given in the passage above


216) When the forward bias voltage of a diode is changed from 0.6 V to 0.7 V, the current changes from 5 mA to
15 mA. Then its forward bias resistance is


217) In an intrinsic semiconductor, the Fermi level is


218) The potential in depletion layer is due to


219) A p-n photodiode is made of a material with a band gap of 2.0 eV. The minimum frequency of the radiation
that can be absorbed by the material is nearly


220) In an intrinsic semiconductor,the Fermi level is


221) Formation of covalent bonds in compounds exhibits


222) The current gain of a transistor in common base mode is 0.995. the current gain of the same transistor in
common emitter mode is


223) The temperature coefficient of resistance of a semiconductor


224) Carbon, silicon and germanium have four valence electrons each. At room temperature which one of the
following statements is more appropriate?


225) If a full wave rectifier circuit is operating from 50Hz mains, the fundamental frequency in the ripple will be


226) The electrical circuit used to get smooth DC output from a rectifier circuit is called


227) A piece of semiconductor is connected in series in an electric circuit. On increasing the temperature, the
current in the circuit will


228) For a common emitter amplifier, the audio signal voltage across the collector resistance 2kΩ is 2 V. If the
current amplification factor of the transistor is 220, and the base resistance is 1.5 Ω, the input signal
voltage and base current are


229) If the forward voltage in a semiconductor diode is changed from 0.5 V to 0.7 V, then the forward current
changes by 1.0 mA. The forward resistance of diode junction will be


230) The temperature coefficient of resistance of semiconductor


231) If no external voltage is applied across P-N junction,there would be


232) The current gain of transistor base mode is 0.995. The current gain of same transistor is


233) In CE mode,the input characteristics of transistor is the variation of


234) Which of the following is a dichroic crystal


235) Zener breakdown in a semi-conductor diode occurs when


236) The difference in the variation of resistance with temperature in a metal and a semiconductor arises
essentially due to the difference in th


237) The coordination number of hexagonal close packing (hcp) is


238) The typical ionisation energy of a donor in silicon is


239) Consider the following statements A and
B and identify the correct choice of the given answers
A. The width of the depletion layer in a
P - N junction diode increases in forward bias
B.In an intrinsic semiconductor the fermi energy level is exactly in the middle of the forbidden gap


240) In N - type semiconductors, majority charge carriers are


241) In the following,which one of the diodes is reversed biased?


242) In a triode,cathode,grid and plate are at 0, -2, and 80V respectively,The electrons are emitted from the cathode with energy 3eV.The energy of the electron reaching the plate is


243) Resistance of a semiconductor


244) In a common emitter amplifier the input signal is applied across


245) The phenomenon of thermionic emission was discovered by


246) In depletion layer of unbiased p-n junction


247) Carbon,silicon and germanium have four valence electron each.At room temperature which one of the following statements is more appriciate?


248) The output of NAND gate is 0


249) What is the name of level due to impurity atom in P -type in the forbidden gap


250) Which of the following gates will have an output of 1.


251) In N-type semiconductors,majority charge carriers are


252) In the middle of the depletion layer of reverse biased p-n junction, the


253) In the circuit of a triode value,there is no change in the plate current,when the plate potential is increased from 200 V and the grid potential is decreased from -0.5V to -1.3V.The amplification factor of value us


254) In a triode amplifier ,the value of maximum gain is equal to


255) P -type semiconductor is formed when

A. As impurity is mixed in Si.
B. Al impurity is mixed in Si.
C. B impurity is mixed in Ge.
D.P impurity is mixed in Ge.


256) A piece of a semiconductor is connected in series in an electric circuit .On increasing the temperature ,the current in the circuit will


257) A p-type material is electricity ................


258) Which of the following statement is not correct when a junction diode is forward bias?


259) If forward voltage in a semiconductor diode is changed from 0.5V t 0.7V,then the forward current changes by 1.0 mA.the forward resistance of diode junction will be


260) Any digital circuit can be realized by repetitive use of only


261) In p-n junction, the barrier potential offers resistance to


262) Would there any advantage
to adding n-type or p-type impurities in copper


263) The co -ordination number of hexagonal close packing (hcp) is


264) The typical ionization energy of a donor in silicon is


265) Consider the following statement A and B and identify the correct choice of the given answers .
A.A width of the depletion layer in a P-N junction diode increases in forward bias

B.In an intrensic semiconductor the fermi level is exactly in the middle of the forbidden gap


266) In an unbiased p-n junction


267) In the presence of interspace charge at plate voltage of 200 v ,the current is 80 mA. Then the current in mA at 400 V will be


268) Resistance of semiconductor


269) In a transistor the base is


270) Name of a p-n junction, which can be used as the regulator, is


271) A strip of copper and another of germanium are cooled from room temperature to 80 K the resistance of


272) Number of secondary electrons emitted per number of primary electrons depends on


273) Wires P and Q have the same resistance at ordinary (room) temperature. When heated, resistance of P
increases and that of Q decreases. We conclude that


274) Diode valve is discovered by


275) Current gain in common base configuration is less than 1 because


276) Digital circuit can be made by repetitive use of this gate


277) The value of ripple factor for full wave rectifier is


278) The valence band and conduction band of a solid overlap at low temperature, the solid may be


279) The ratio of slopes of anode characteristics and mutual characteristic curves is said to be


280) The coordination number of body centred crystal is


281) To a germanium sample, traces of gallium are added as an impurity. The resultant sample would behave
like


282) P-N junction is said to be forward biased, when


283) Identify the true statement for OR gate


284) Barrier potential of a p-n junction diode does not depend on


285) The part of a transistor which is heavily doped to produce a large number of majority carriers is


286) In a P-type semiconductor, the acceptor impurity produces an energy level


287) If the output of a logic gate is 0 when all its inputs are at logic
1, then the gate is either


288) In LED visible light is produced by


289) Due to S.C.R. in vacuum tube


290) The Fermi level of an intrinsic semiconductor is pinned at the centre of the band gap. The probability of
occupation of the highest electron state in valence band at room temperature, will be


291) Plate current in a diode depends


292) The saturation current in a diode valve is governed by


293) In order to prepare a p-type semiconductor, pure silicon can be doped with


294) In a transistor the collector current is always less than the emitter current because


295) The difference in the variation of resistance with temperature in a metal and a semiconductor arises essentially due to the difference in the


296) A photodetector used to detect the wavelength of 1700nm,has energy gap of about


297) A piece of copper and another of germanium are cooled from room temperature to 77K ,the resistance of


298) which of the following has negative temperature coefficient of resistance.


299) In an n-type semiconductor, the fermi energy level lies


300) In colpit oscillator the feedback network consists of


301) Which of the following is amorphous substance?


302) A metallic surface with work function of 2 eV, on heating to a temperature of 800 K gives an emission
current of 1 mA. If another metallic surface having the same surface area, same emission constant but
work function 4 eV is heated to a temperature of 1600 K, then the emission current will be


303) When boron is added as an impurity to silicon, the resulting material is


304) The PN junction diode is used as


305) The typical ionisation energy of a donar in silicon is


306) Which circuit will not show current in ammeter


307) The logic behind ‘NOR’ gate is that it gives


308) How many NAND gates are required to form an AND gate?


309) A solid which is not transparent to visible light and whose electrical conductivity increases with
temperature is formed by


310) The output of OR gate is 1


311) A transistor is used as an amplifier in CB mode with a load resistance of 5 k Ω. The current gain of amplifier is 0.98 and the input resistance is 70 Ω, the voltage gain and power gain respectively are


312) The current gain α of a transistor in common base mode is 0.995. Its gain β in the common emitter mode is


313) In a n-p-n transistor, the collector current is 10mA. If 90% of the electrons emitted reach the collector,
then the emitter current will be


314) A pure semiconductor behaves slightly as a conductor at


315) The nature of binding for a crystal with alternate and evenly spaced positive and negative ions is


316) Doping of a semiconductor (with small traces of impurity atoms) generally changes the resistivity as
follows


317) Radiowaves of constant amplitude can be generated with


318) When the plate voltage of a triode is 150V, its cut-off voltage is −5 V. On increasing the plate voltage to 200
V, the cut-off voltage can be


319) The mutual characteristic of triode is


320) In a forward biased p-n junction diode, the potential barrier in the depletion region is of the form


321) What makes the crystalline solids have a sharp melting point?


322) Symbolic representation of photodiode is


323) Choose the correct statement


324) The current gain of a common base transistor circuit is 0.96. On changing the emitter current by 10.0 mA,
the change in the base current will be


325) The manifestation of band structure in solids is due to decreases the majority charge carries


326) A crystal diode is a


327) Coating of strontium oxide on tungsten cathode in a valve is good for thermionic emission because


328) In an NPN transistor the collector current is 24 mA. If 80% of electrons reach collector its base current in mA is


329) Of the following which relation is true?


330) In case of a semiconductor, which of the following statement is wrong


331) Which of the following logic gate is an universal gate


332) The correct curve between potential (V) and distance (d) near p - n junction is


333) Reverse bias applied to a p-n junction diode


334) Consider an NPN transistor amplifier in common-emitter configuration. The current gain of the transistor is 100. If the collector current changes by 1 mA, what will be the change in emitter current


335) The electrical conductivity of an intrinsic semiconductor at 0 K is


336) Change in temperature


337) The energy of radiation emitted by LED is


338) In a semiconductor


339) In a n-p-n transistor amplifier, the collector current is 9 mA. If 90% of the electrons from the emitter reach the collector, then


340) In p-type semiconductors, conduction is due to


341) When plate voltage in diode valve is increased from 100 volt to 150 volt then plate current increases from 7.5 mA to 12 mA. The dynamic plate resistance will be


342) The collector supply voltage is 6 V and the voltage drop across a resistor of 600 Ω in the collector circuit is 0.6 V, in a transistor connector in common emitter mode. If the current gain is 20, the base current is


343) In a p-n junction diode


344) An alternating current can be converted into direct current by a


345) Electronic configuration of germanium is 2, 8, 18 and 4. To make it extrinsic semiconductor small quantity of antimony is added.


346) In BJT, maximum current flows in which of the following?


347) A solid reflects incident light and its electrical conductivity decreases with temperature. The binding in
this solid is


348) When p-n junction diode is forward biased then


349) Pick out the statement which is not correct


350) When a solid with a band gap has a donor level just below its empty energy band, the solid is


351) For a transistor amplifier, the voltage gain


352) A piece of copper and other of germanium are cooled from the room temperature to 80 K, then


353) Identify the property which is not characteristic for a semiconductor?


354) Which of the following is forward biased?


355) The curve between charge density and distance near P-N junction will be


356) Semiconductor is damaged by the strong current due to


357) Diode is used as a/an


358) What is the coordination number of sodium ions in the case of sodium chloride structure?


359) A transistor oscillator is
(i) An amplifier with positive feedback
(ii) An amplifier with reduced gain
(iii) The one in which DC supply energy is converted into AC output energy. Then


360) In silicon when phosphorus is doped...................is formed.


361) When a p-n junction diode is reverse biased, then


362) when phosphorus and antimony are mixed in germanium,then


363) Atomic packing factor for a face centred cubic cells


364) For a given plate-voltage, the plate current in a triode is maximum when the potential of


365) In a diode,when there is saturation current,the plate resistance will be


366) In an experiment the saturation in the plate current in a diode is observed at 240V. But a student still wants to increase the plate current. It can be done ,if


367) The emitter-base junction of a transistor is ............... biased while the collector-base junction is ..................
biased


368) The maximum efficiency of full wave rectifier is


369) The expected energy of the electrons at absolute zero is called


370) A transistor has a base current of 1 mA and emitter current 90 mA. The collector current will be


371) Current gain in common emitter configuration is more than 1 becomes


372) Avalanche breakdown in a p-n junction diode is due to


373) Resistivity of a semiconductor depends on


374) For an insulator the forbidden energy gap is


375) In semiconductors at a room temperature


376) The ionic bond is absent in


377) Different voltages are applied across a p-n junction and the currents are measured from each value. Which of the following graphs is obtained between voltage and current?


378) How many NAND gates are used in an OR gate?


379) The electrical resistance of depletion layer is large because


380) If control grid is made negative, then the plate current will


381) Zener breakdown takes place if


382) In a P-type semiconductor


383) Bonding in a germanium crystal (semi-conductor) is


384) The binary number 10111 is equivalent to the decimal number


385) if the forward voltage in a diode is increased, the width of the depletion region


386) The n-type semiconductors are obtained, when germanium is doped with


387) In forward bias, the width of potential barrier in a P-N junction diode


388) In a P-N junction diode if
P region is heavily doped than n region then the depletion layer is


389) A n-p-n transistor having a.c. current gain of 50 is to be used to make an amplifier of power gain of 300. What will be the voltage gain of the amplifier


390) Electric conduction in semi-conductor takes place due to


391) For germanium crystal, the forbidden energy gap in joules is


392) In an insulator, the forbidden energy gap between the valance band and conduction band is of the order of


393) The ratio of work functions and temperatures of two emitters are 1 : 2, then the ratio of current densities obtained by them will be


394) In P-N junction, avalanche current flows in circuit when biasing is


395) In a P-type semi-conductor, germanium is dopped with


396) The gate for which output is high, if at least one input is low?


397) The phase
difference between input and output voltages of a CE circuit is


398) To a germanium crystal equal number of aluminium and indium atoms are added. Then


399) In a common base transistor circuit, the current gain is 0.98. On changing emitter current by 5.00 mA, the change in collector current is


400) While using triode as
an amplifier, we avoid making the grid positive because


401) Why do we prefer indirectly heated cathode to the directly heated cathode?


402) Which of the following is not a process involved in fabrication of IC


403) p-type semiconductor are


404) The temperature of germanium is decreased from room temperature to 100 K, the resistance of germanium


405) An n-type semiconductor is


406) Biaxial crystal among the following is


407) 14× 10¹⁵electrons reach the anode per second. If the power consumed is 448milli watts then the plate
(anode) voltage is


408) The ripple factor in a half wave rectifier is


409) The reverse saturation of p-n diode


410) The phase difference between input and output voltages of a CE circuit is


411) Diode is not considered as linear device because


412) While using triode as an amplifier, we avoid making the grid positive because,


413) Least doped region in a transistor


414) The main cause of zener breakdown is


415) A Si and a Ge diode has identical physical dimensions. The band gap in Si is larger than that in Ge. An identical reverse bias is applied across the diodes


416) Why is there sudden increase in current in zener diode?


417) C and Si both have same lattice structure, having 4 bonding electrons in each. However, C is insulator where as Si is intrinsic semiconductor. This is because


418) Which of the following materials in non crystalline


419) The addition of antimony atoms to a sample of intrinsic germanium transforms it to a material which is


420) A semiconductor device is connected in a series circuit with a battery and a resistance. A current is found
to pass through the circuit. If the polarity of the battery is revered, the current drops almost to zero. The
device may be


421) The voltage gain of an amplifier with 9% negative feedback is 10. The voltage gain without feedback will be


422) The charge on a hole is equal to the charge of


423) The difference in the variation of resistance with temperature in a metal and a semiconductor arises
essentially due to the difference in the


424) Regarding a semiconductor which one of the following is wrong


425) Bonds in semiconductor are


426) The temperature coefficient of a zener mechanism is


427) In the presence of space charge in the diode valve the plate current is 10mA at the plate voltage 50V. Then the plate current at plate voltage 200 V will be


428) Which of the following is not equal to 1 in Boolean algebra?


429) The temperature coefficient of resistance of a conductor is


430) Which one of the following is the weakest kind of bonding in solids


431) Donor type impurity is found in


432) The Binary Coded Decimal (BCD) equivalent of 429 is


433) In a transistor in common-emitter configuration, the ratio of power gain to voltage gain is


434) In breakdown region, a zener diode behaves as a


435) A triode whose mutual conductance is 2.5 m A/volt and anode resistance is 20 killo ohm, is used as an
amplifier whose amplification is 10. The resistance connected in plate circuit will be


436) Avalanche breakdown is due to


437) An oscillator in nothing but an amplifier with


438) In order to rectify an alternating current one uses a


439) Metallic solids are always opaque because


440) The coordination number of simple cubic crystal is


441) Energy bands in solids are a consequence of


442) Which of the following materials is the best conductor of electricity


443) Which one is in forward bias


444) Which of the energy band diagrams shown in the figure corresponds to that of a semiconductor?


445) The probability of electrons to be found in the conduction band of an intrinsic semiconductor at a finite
temperature


446) In a properly biased transistor


447) Which represents NAND gate


448) The resistivity of a semiconductor at room temperature is in between


449) When the electrical of a semi- conductor is due to the breaking of its covalent bonds, then the semiconductor is said to be


450) Silicon is a semiconductor. If a small amount of As is added to it, then its electrical conductivity


451) When a battery is connected to a P-type semiconductor with a metallic wire, the current in the
semiconductor (predominantly), inside the metallic wire and that inside the battery respectively is due to


452) Identify the incorrect statement regarding a superconducting wire


453) The current gain of a transistor in the common base mode is 0.9. If the change in the emitter current is 5
mA, the change in the collector current will be


454) To write the decimal number 37 in binary, how many binary digits are required


455) For a cubic crystal structure which one of the following relations indicating the cell characteristic is
correct?


456) Zener diode is used as


457) When the forward biased voltage of a diode is changed from 0.6V to 0.7V,the current changes from 5mA to 15mA,then forward bias resistance is


458) In triode,cathode,grid and plate are at 0,-2 and 80V respectively.The electrons are emitted from the cathode with energy 3 eV.The electrons reaching the plate is


459) When germanium is doped with phosphorus, the doped material has


460) Which of these is unipolar transistor