NEET AIPMT Physics Chapter Wise Solutions - Semiconductor Electronics: Materials, Devices and Simple Circuits

NEET AIPMT Physics Chapter Wise Solutions – Semiconductor Electronics: Materials, Devices and Simple Circuits

1. The input signal given to a CE amplifier having a voltage gain of 150 is ${ V }_{ i }=2cos\left( 15t+\frac { \pi }{ 3 } \right)$ The corresponding output signal will be

2. In the given figure, a diode D is connected to an external resistance R = 100 Ω and an e.m.f. of 3.5 V. If the barrier potential developed across the diode is 0.5 V, the current in the circuit will be (AIPMT 2015)
(a) 20 mA
(b) 35 mA
(c) 30 mA
(d) 40 mA

3. Which logic gate is represented by the following combination of logic gates? (AIPMT 2015, Cancelled)
(a) AND
(b) NOR
(c) OR
(d) NAND

4. If in a p-n junction, a square input signal of 10 V is applied, as shown, then the output across R_Lwill be

5. The given graph represents V-I characteristic for a semiconductor device.

Which of the following statement is correct? (AIPMT 2014)

(a) It is V-I characteristic for solar cell where, point A represents open circuit voltage and point B short circuit current.
(b) It is for a solar cell and points A and B represent open circuit voltage and current, respectively.
(c) It is for a photodiode and points A and B represent open circuit voltage and current, respectively.
(d) It is for a LED and points A and B represent open circuit voltage and short circuit current, respectively.

6. The barrier potential of a p-n junction depends on

type of semiconductor material
amount of doping
temperature

Which one of the following is correct? (AIPMT 2014)

(a) (1) and (2) only
(b) (2) only
(c) (2) and (3) only
(d) (1), (2) and (3)

7. In a common emitter (CE) amplifier having a voltage gain G, the transistor used has j transconductance 0.03 mho and current gain 25 , If the above transistor is replaced with another j one with transconductance 0.02 mho and current i gain 20, the voltage gain will be (NEET 2013)

(a) 1/3 G
(b) 5/4 G
(c) 2/3 G
(d) 1.5 G

8. In a n-type semiconductor, which of the following statement is true. (NEET 2013)

(a) Holes are minority carriers and pentavalent atoms are dopants.
(b) Holes are majority carriers and trivalent atoms are dopants.
(c) Electrons are majority carriers and trivalent atoms are dopants.
(d) Electrons are minority carriers and pentavalent atoms are dopants.

9. The output (X) of the logic circuit shown in figure will be (NEET 2013)

10. The output from a NAND gate is divided into two in parallel and fed to another NAND gate. The resulting gate is a (Karnataka NEET 2013)

(a) AND gate
(b) NOR gate
(c) OR gate
(d) NOT gate

11. One way in which the operation of a n-p-n transistor differs from that of a p-n-p (Karnataka NEET 2013)

(a) The emitter junction injects minority carriers into the base region of the p-n-p
(b) The emitter injects holes into the base of the p-n-p and electrons into the base region of n-p-n
(c) The emitter injects holes into the base of n-p-n
(d) The emitter junction is reversed biased in n-p-n

12. In an unbiased p-n junction, holes diffuse from the p-region to n-region because of (Karnataka NEET 2013)

(a) The attraction of free electrons of n-region.
(b) The higher hole concentration in p-region than that in n-region.
(c) The higher concentration of electrons in the n-region than that in the p-region.
(d) The potential difference across the p-n junction.

13. Two ideal diodes are connected to a battery as shown in the circuit. The current supplied by the battery is

(a) 75 A
(b) zero
(c) 25 A
(d) 5 A

14. In a CE transistor amplifier, the audio signal voltage across the collector resistance of 2 kΩ is 2 V. If the base resistance is 1 kΩ and the current amplification of the transistor is 100, the input signal voltage is (Prelims 2012)

(a) 1 V
(b) 1.0 V
(c) 1 mV
(d) 10 mV

15. 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 (Prelims 2012)

(a) In case of C the valence band is not completely filled at absolute zero temperature.
(b) In case of C the conduction band is partly filled even at absolute zero temperature.
(c) The four bonding electrons in the case of C lie in the second orbit, whereas in the case of Si they lie in the third.
(d) The four bonding electrons in the case of C lie in the third orbit, whereas for Si they lie in the fourth orbit.

16. Transfer characteristics [output voltage (V₀) vs input voltage (V_i) for a base biased transistor in CE configuration is as shown in the figure. For using transistor as a switch, it is used (Prelims 2012)

(a) in region III
(b) both in region (I) and (III)
(c) in region II
(d) in region I

17. The figure shows a logic circuit with two inputs A and B and the output C. The voltage wave forms across A, B and C are as given. The logic circuit gate is (Prelims 2012)

(a) OR gate
(b) NOR gate
(c) AND gate
(d)NAND gate

18. The input resistance of a silicon transistoe is 100 Ω. Base current is changed by 40 μA which results in a change in collector currently by 2 mA. This transistor is used as a common emitter amplifier with a load resistance of 4 kΩ. The voltage gain of the amplifier is (Mains 2012)

(a) 2000
(b) 3000
(c) 4000
(d) 1000

19. To get an output Y = 1 in given circuit which of the following input will be correct?

(a) 1 0 0
(b) 1 0 1
(c) 1 1 0
(d) 0 1 0

20. A transistor is operated in common emitter configuration at V_c = 2 V such that a change in the base current from 100 μA to 300 μA produces a change in the collector current from 10 mA to 20 mA. The current gain is (Prelims 2011)

(a) 50
(b) 75
(c) 100
(d) 25

21. In forward biasing of the p-n junction (Prelims 2011)

(a) the positive terminal of the battery is connected to p-side and the depletion region becomes thick.
(b) the positive terminal of the battery is connected to n-side and the depletion region becomes thin.
(c) the positive terminal of the battery is connected to n-side and the depletion region becomes thick.
(d) the positive terminal of the battery is connected to p-side and the depletion region becomes thin.

22. Symbolic representation of four logic gates are shown as
Pick out which ones are for AND, NAND and NOT gates, respectively (Prelims 2011)

(a) (ii), (iii) and (iv)
(b) (iii), (ii) and (i)
(c) (iii), (ii) and (iv)
(d) (ii), (iv) anti (iii)

23. If a small amount of antimony is added to germanium crystal , (Prelims 2011)

(a) it becomes a p-type semiconductor (b) the antimony becomes an acceptor atom
(c) there will be more free electrons than holes in the semiconductor
(d) its resistance is increased

24. A Zener diode, having breakdown voltage equal to 15V, is used in a voltage regulator circuit shown in figure. The current through the diode is (Mains 2011)

(a) 5 mA
(b) 10 mA
(c) 15 mA
(d) 20 mA

25. In the following figure, the diodes which are forward biased, are (Mains 2011)

(a) (A), (B) and (D)
(b) (C) only
(c) (C) and (A)
(d) (B) and (D)

26. Pure Si at 500 K has equal number of electron (n_e) and hole (n_h) concentrations of 1.5 x 10¹⁶ m^-3. Doping by indium increases n_h to 4.5 x 10²² m^-3. The doped semiconductor is of (Mains 2011)

(a) p-type having electron concentration n_e =5 x 10⁹m^-3(b) n-type with electron concentration n_e = 5 x 10²²m^-3(c) p-type with electron concentration n_e =2.5 x 10¹⁰m^-3(d) n-type with electron concentration n_e = 2.5 x 10²³ m^-3

27. Which one of the following statement is false? (Prelims 2010)

(a) Pure Si doped with trivalent impurities gives a p-type semiconductor.
(b) Majority carriers in a n-type semiconductor are holes.
(c) Minority carriers in a p-type semiconductor are electrons.
(d) The resistance of intrinisic semiconductor decreases with increase of temperature.

28. Which one of the following bonds produces a solid that reflects light in the visible region and whose electrical conductivity decreases with temperature and has high melting point? (Prelims 2010)

(a) metallic bonding
(b) van der Waal’s bonding
(c) ionic bonding
(d) covalent bonding

29. The device that can act as a complete electronic circuit is (Prelims 2010)

(a) junction diode
(b) integrated circuit
(c) junction transistor
(d) zener diode

30. A common emitter amplifier has a voltage gain of 50, an input impedance of 100 Ω and an output impedance of 200 Ω. The power gain of the amplifier is (Prelims 2010)

(a) 500
(b) 1000
(c) 1250
(d) 50

31. To get an output Y = 1 from the circuit shown below, the input must be (Prelims 2010)

(a) 0 1 0
(b) 0 0 1
(c) 1 0 1
(d) 1 0 0

32. The following figure shows a logic gate circuit with two inputs A and B and the output Y. The voltage wave forms of A, B and Y are as given. (Mains 2010)

(a) NOR gate
(b) OR gateThe logic gate is
(c) AND gate
(d) NAND gate

33. For transistor action

Base, emitter and collector regions should have similar size and doping concentrations.
The base region must be very thin and lightly doped.
The emitter-base junction is forward biased and base-collector junction is reverse biased.
Both the emitter-base junction as well as the base-collector junction are forward biased.

Which one of the following pairs of statements is correct? (Mains 2010)

(a) (4) and (1)
(b) (1) and (2)
(c) (2) and (3)
(d) (3) and (4)

34. A p-n photodiode is fabricated from a semiconductor with a band gap of 2.5 eV. iHcan detect a signal of wavelength (Prelims 2009)

(a) 4000 nm
(b) 6000 nm
(c) 4000 Å
(d) 6000 Å

35. The symbolic representation of four logic gates are given below
The logic symbols for OR, NOT and NAND gates are respectively (Prelims 2009)

(a) (iv), (i), (iii)
(b) (iv), (ii), (i)
(c) (i), (iii), (iv)
(d) (iii), (iv), (ii)

36. A transistor is operated in common-emitter configuration at V_c = 2 V such that a change in the base current from 100 μA to 200 μA produces a change in the collector current from 5 mA to 10 mA. The current gain is (Prelims 2009)

(a) 100
(b) 150
(c) 50
(d) 75

37. Sodium has body centred packing. Distance between two nearest atoms is 3.7 The lattice parameter is (Prelims 2009)

(a) 4.3 Å
(b) 3.0 Å
(c) 8.6 Å
(d) 6.8 Å

38. The circuit is equivalent to (Prelims 2008)

(a) NOR gate
(b) OR gate
(c) AND gate
(d) NAND gate

39. 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 (Prelims 2008)

(a) 1 x 10¹⁴Hz
(b) 20 x 10¹⁴ Hz
(c) 10 x 10¹⁴Hz
(d) 5 x 10¹⁴Hz

40. If the lattice parameter for a crystalline structure is 3.6 Å, then the atomic radius in fee crystal is (Prelims 2008)

(a) 2.92 Å
(b) 1.27 Å
(c) 1.81 Å
(d) 2.10 Å

41. The voltage gain of an amplifier with 9% negative feedback is 10. The voltage gain without feedback will be (Prelims 2008)

(a) 1.25
(b) 100
(c) 90
(d) 10

42. In the following circuit, the output Y for all possible inputs A and B is expressed by the truth table.

43. A common emitter amplifier has a voltage gain of 50, an input impedance of 100 Ω and an output impedence of 200 Ω. The power gain of the amplifier is (200 7)

(a) 1000
(b) 1250
(c) 100
(d) 500.

44. For a cubic crystal structure which one of the following relations indicating the cell characteristics is correct? (2007)

(a) a ≠ b ≠ c and α = β = γ = 90°
(b) a = b = c and α ≠ β ≠ γ = 90°
(c) a = b = c and α = β = γ = 90°
(d) a ≠ b ≠ c and α ≠ β and γ ≠ 90°.

45. In the energy band diagram of a material shown below, the open circles and filled circles denote holes and electrons respectively. The material is (2007)

(a) an insulator
(b) a metal
(c) an n-type semiconductor
(d) a p-type semiconductor.

46. A forward biased diode is (2006)

47. The following figure

shows a logic gatecircuit with two inputs A and B and the output C.
The voltage waveforms .of A, B and C are as shown below. (2006)

The logic circuit gate is

(a) OR gate
(b) AND gate
(c) NAND gate
(d) NOR gate.

48. A transistor is operated in common emitter configuration at constant collector voltage V_c=5 V such that a change in the base current from 100 μA to 150 μA produces a change in the collector current from 5 mA to 10 mA. The current gain β is (2006)

(a) 50
(b) 67
(c) 75
(d) 100.

49. Choose the only false statement from the following.

(a) In conductors the valence aijd conduction bands overlap.
(b) Substances with energy gap of the order of 10 eV are insulators.
(c) The resistivity of a semiconductor increases with increase in temperature.
(d) The conductivity of a semiconductor increases with increase in temperature.

50. Zener diode is used for (2005)

(a) amplification
(b) rectification
(c) stabilisation
(d) producing oscillations in an oscillator.

51. Application of a forward bias to a p-n junction (2005)

(a) widens the depletion zone
(b) increases the potential difference across the depletion zone
(c) increases the number of donors on the n side
(d) decreases the electric field in the depletion zone.

52. Carbon, silicon and germanium atoms have four valence electrons each. Their valence and conduction bands are separated by energy band gaps represented by (E_g)_c, (E_g)_si and (E_g)_Ge Which one of the following relationships is true in their case? (2005)

(a) (E_g)_c > (E_g)_si
(b) (E_g)_c < (E_g)_si(c) (E_g)_c = (E_g)_si
(d) (E_g)_c < (E_g)_Ge.

53. Copper has face centered cubic (fee) lattice with interatomic spacing equal to 2.54 The value of lattice constant for this lattice is (2005)

(a) 54 A
(b) 3.59 A
(c) 1.27 A
(d) 5.08 A.

54. In a p-n junction photo cell, the value of the photo-electromotive force produced by monochromatic light is proportional to (2005)

(a) The barrier voltage at the p-n
(b) The intensity of the light falling on the cell.
(c) The frequency of the light felling on the cell.
(d) The voltage applied at the p-n

55. In semiconductors at a room temperature (2004)

(a) the valence band is partially empty and the conduction band is partially filled
(b) the valence band is completely filled and the conduction band is partially filled
(c) the valence band is completely filled
(d) the conduction band is completely empty

56. The peak voltage in the output of a half wave diode rectifier fed with a sinusoidal signal without filter is 10 V. The d.c. component of the output voltage is (2004)

(a) 10√2 V
(b) 10/π V
(c) 10 V
(d) 20/π V

57. The output of OR gate is 1 (2004)

(a) if both inputs are zero
(b) if either or both inputs are 1
(c) only if both inputs are 1
(d) if either input is zero

58. Of the diodes shown in the following diagrams, which one is reverse biased ?

59. Reverse bias applied to a junction diode (2003)

(a) lowers the potential barrier
(b) raises the potential barrier
(c) increases the majority carrier current
(d) increases the minority carrier current

60. A n-p-n transistor conducts when (2003)

(a) both collector and emitter are positive with respect to the base
(b) collector is positive and emitter is negative with respect to the base
(c) collector is positive and emitter is at same potential as the base
(d) both collector and emitter are negative with respect to the base

61. If a full wave rectifier circuit is operating from 50 Hz mains, the fundamental frequency in the ripple will be (2003)

(a) 25 Hz
(b) 50 Hz
(c) 70.7 Hz
(d) 100 Hz

62. Barrier potential of a p-n junction diode does not depend on (2003)

(a) diode design
(b) temperature
(c) forward bias
(d) doping density

63. Following diagram performs the logic function of (2003)

(a) AND gate
(b) NAND gate
(c) OR gate
(d) XOR gate

64. Number of atom per unit cell in B.C.C. (2002)

(a) 9
(b) 4
(c) 2
(d) 1.

65. For a transistor I_c/I_e= 0.96, then current gain for common emitter is (2002)

(a) 12
(b) 6
(c) 48
(d) 24.

66. In a p-n junction

(a) high potential at n side and low potential at p side
(b) high potential at p side and low potential at n side
(c) p and n both are at same potential
(d) undetermined

67. The given truth table is for which logic gate (2002, 2001, 1998, 94)

(a) NAND
(b) XOR
(c) NOR
(d) OR

68. For the given circuit of p-n junction diode which is correct (2002)

(a) in forward bias the voltage across R is V
(b) in reverse bias the voltage across R is V
(c) in forward bias the voltage across R is 2V
(d) in reverse bias the voltage across R is 2F.

69. The current in the circuit will be (2001)

(a) 5/40 A
(b) 5/50 A
(c) 5/10 A
(d) 5/20 A

70. For a common base circuit if I_c/I_e =0.98 then current gain for common emitter circuit will be (2001)

(a) 49
(b) 98
(c) 4.9
(d) 25.5.

71. The cations and anions are arranged in alternate form in (2000)

(a) metallic crystal
(b) ionic crystal
(c) covalent crystal
(d) semi-conductor crystal.

72. From the following diode circuit, which diode is in forward biased condition

73. The correct relation for α, β for a transistor

74. A p-n junction diode can be used as

(a) condenser
(b) regulator
(c) amplifier
(d) rectifier

75. Sodium has body-centred packing. If the distance between two nearest atoms is 3.7 Å, then lattice parameter is (1999)

(a) 4.3 Å
(b) 39 Å
(c) 3.3 Å
(d) 4.8 Å

76. In a p type semiconductor, the majority carriers of current are (1999)

(a) protons
(b) electrons
(c) holes
(d) neutrons

77. In forward bias, the width of potential barrier in a p-n junction diode (1999)

(a) remains constant
(b) decreases
(c) increases
(d) first (a) then (b)

78. Depletion layer consists of (1999)

(a) mobile ions
(b) protons
(c) electrons
(d) immobile ions

79. In a junction diode, the holes are due to (1999)

(a) extra electrons
(b) neutrons
(c) protons
(d) missing of electrons

80. Which of the following, when added as an impurity into the silicon produces n type semiconductor? (1999)

(a) B
(b) AI
(c) P
(d) Mg

81. The cause of the potential barrier in a p-n diode is (1998)

(a) depletion of negative charges near the junction
(b) concentration of positive charges near the junction
(c) depletion of positive charges near the junction
(d) concentration of positive and negative charges near the junction

82. Which of the following gates will have an output of 1?

83. The transfer ratio (3 of a transistor is 50. The input resistance of the transistor when used in the common-emitter configuration is 1 kΩ. The peak value of the collector A.C. current for an A.C. input voltage of 0.01 V peak is

(a) 0.25 mA
(b) 0.01 mA
(c) 100 μA
(d) 500 μA

84. A semiconducting 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 reversed, the current drops to almost zero. The device may be (1998)

(a) a p type semiconductor
(b) an intrinsic semiconductor
(c) a p-n junction
(d) an n type semiconductor

85. The diode used in the circuit shown in the figure has a constant voltage drop at 0.5 V at all currents and a maximum power rating of 100 milli watts. What should be the value of the resistor R, connected in series with diode for obtaining maximum current? (1997)

(a) 6.76 Ω
(b) 20 Ω
(c) 5 Ω
(d) 5.6 Ω.

86. The correct relationship between the two current gains a and b in a transistor is

87. The following truth-table belongs to which one of the following four gates? (1997, 95)

(a) XOR
(b) NOR
(c) OR
(d) NAND

88. To obtain a p-type germanium semiconductor, it must be doped with (1997)

(a) indium
(b) phosphorus
(c) arsenic
(d) antimony.

89. When n-p-n transistor is used as an amplifier, then (1996)

(a) electrons move from collector to base
(b) holes move from base to emitter
(c) electrons move from base to collector
(d) electrons move from emitter to base.

90. When arsenic is added as an impurity to silicon, the resulting material is (1996)

(a) n-type conductor
(b) n-type semiconductor
(c) p-typc serhiconductor
(d) none of these.

91. When using a triode, as an amplifier, the electrons are emitted by (1996)

(a) grid and collected by cathode only
(b) cathode and collected by the anode only
(c) anode and collected by cathode only
(d) anode and collected by the grid and by cathode.

92. This symbol represents

(a) AND gate
(b) NOR gate
(c) NAND gate
(d) OR gate.

93. Distance between body centred atom and a comer atom in sodium (a =225 Å) is (1995)

(a) 2.99 Å
(b) 2.54 Å
(c) 3.66 Å
(d) 3.17 Å.

94. In the case of forward biasing of p-n junction, which one of the following figures correctly depicts the direction of flow of carriers?

95. Diamond is very hard because (1993)

(a) it is covalent solid
(b) it has large cohesive energy
(c) high melting point
(d) insoluble in all solvents

96. The part of the transistor which is hitavily doped to produce large number of majority carriers is (1993)

(a) emitter
(b) base
(c) collector
(d) any of the above depending upon the nature of transistor

97. Which one of the following is the weakest kind of the bonding in solids? (1992)

(a) ionic
(b) metallic
(c) van der Waals
(d) covalent

98. For amplification by a triode, the signal to be amplified is given to

(a) the cathode
(b) the grid
(c) the glass envelope
(d) the anode

99. For an electronic valve, the plate current I and plate voltage V in the space charge limited region are related as (1992)

(a) I is proportional to V^3/2(b) I is proportional to V^2/3(c) I is proportional to V
(d) I is proportional to V²

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

(a) resistance of each will increase
(b) resistance of copper will decrease
(c) the resistance of copper will increase while that of germanium will decrease
(d) the resistance of copper will decrease while that of germanium will increase

101. The depletion layer in the p-n junction region is caused by (1991)

(a) drift of holes
(b) diffusion of charge carriers
(c) migration of impurity ions
(d) drift of electrons.

102. The following truth table corresponds to the logical gate (1991)

(a) NAND
(b) OR
(c) AND
(d) XOR.

103. To use a transistor as an amplifier (1991)

(a) the emitter base junction is forward biased and the base collector junction is reversed biased
(b) no bias voltage is required
(c) both junction are forward biased
(d) both junction are reverse biased.

104. In a common base amplifier the phase difference between the input signal voltage and the output voltage is (1990)

(a) 0
(b) π/4
(c) π/2
(d) π.

105. When a triode is used as an amplifier the phase difference between the input signal voltage and the output is (1990)

(a) 0
(b) π
(c) π/2
(d) π/4.

106. When n type semiconductor is heated (1989)

(a) number of electrons increases while that of holes decreases
(b) number of holes increases while that of electrons decreases
(c) number of electrons and holes remain same
(d) number of electrons and holes increases equally.

107. Radiowaves of constant amplitude can be generated with (1989)

(a) FET
(b) filter
(c) rectifier
(d) oscillator.

108. p-n junction is said to be forward biased, when (1988 )

(a) the positive pole of the battery is joined to the p-semiconductor and negative pole to the n-semiconductor
(b) the positive pole of the battery is joined to the n-semiconductor and p-semiconductor
(c) the positive pole of the battery is connected to n-semiconductor and p-semiconductor
(d) a mechanical force is applied in the forward direction.

109. At absolute zero, Si acts as (1988)

(a) non metal
(b) metal
(c) insulator
(d) none of these.

ANSWERS