Chapter Semiconductor Electronics

Size: px

Start display at page:

Download "Chapter Semiconductor Electronics"

Julius Greene
6 years ago
Views:

1 Chapter Semiconductor Electronics Q1. 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 the positive pole of the battery is joined to the n- semiconductor and p-semiconductor the positive pole of the battery is connected to n- semiconductor and p-semiconductor a mechanical force is applied in the forward direction Q2. At absolute zero, Si acts as [1988] (a) non-metal metal insulator none of these Q3. When n-type semiconductor is heated [1989] (a) number of electrons increases while that of holes decreases number of holes increases while that of electrons decreases number of electrons and holes remain same number of electrons and holes increases equally. Q4. Radio waves of constant amplitude can be generated with [1989] (a) FET filter rectifier oscillator Q5. In a common base amplifier the phase difference between the input signal voltage and the output voltage is [1990] (a) 0 π/4 π/2 π Q6. When a triode is used as an amplifier the phase difference between the input signal voltage and the output is [1990] (a) 0 π π /2 π /4 Q7. The depletion layer in the p-n junction region is caused by [1991] (a) drift of holes diffusion of charge carriers migration of impurity ions drift of electrons Q8. (a) Q9. To use a transistor as an amplifier [1991] (a) the emitter base junction is forward biased and the base collector junction is reverse biased no bias voltage is required both junctions are forward biased both junctions are reverse biased. Q10. Which one of the following is the weakest kind of bonding in solids [1992] (a) ionic metallic Vander Waal s covalent Q11. For amplification by a triode, the signal to be amplified is given to [1992] (a) the cathode the grid the glass-envelope the anode Q12. For an electronic valve, the plate current Iand plate voltage Vin the space charge limited region are related as [1992] (a) I is proportional to V 3 /2 I is proportional to V 2 /3 I is proportional to V I is proportional to V 2 Q13. Apiece of copper and other of germanium are cooled from the room temperature to 80 K, then (a) resistance of each will increase [1993] resistance of copper will decrease resistance of copper will increase while that of germanium will decrease resistance of copper will decrease while that of germanium will increase

2 Q14. Diamond is very hard because [1993] (a) it is a covalent solid it has large cohesive energy high melting point insoluble in all solvents Q15. The part of the transistor which is heavily doped to produce large number of majority carriers is (a) emitter [1993] base collector any of the above depending upon the nature of transistor Q16. An oscillator is nothing but an amplifer with [1994] (a) positive feedback negative feedback large gain no feedback (a) NAND OR AND XOR Q20. Q17. When a p-n junction diode is reverse biased the flow of current across the junction is mainly due to [1994] (a) diffusion of charges drift of charges depends on the nature of material both drift and diffusion of charges Q18. [1994,02] (a) zero same as the input full wave rectifier half wave rectifier Q21. Which of the following, when added as an impurity, into the silicon, produces n-type semiconductor? [1995] (a) Phosphorous Aluminium Magnesium Both b and c (a) zero same as the input half wave rectified full wave rectified Q19. [1994] [1994] Q22. The current gain for a transistor working as common-base amplifier is0.96. If the emitter current is 7.2 ma, then the base current is (a) 0.29 ma 0.35 ma[1996] 0.39 ma 0.43 ma Q23. When an n p n transistor is used as an amplifier then [1996] (a) the electrons flow from emitter to collector the holes flow from emitter to collector the electrons flow from collector to emitter the electrons flow from battery to emitter

Q24. When arsenic is added as an impurity to silicon, the resulting material is [1996] (a) n-type semiconductor p-type semiconductor n-type conductor insulator Q25.

3 Q24. When arsenic is added as an impurity to silicon, the resulting material is [1996] (a) n-type semiconductor p-type semiconductor n-type conductor insulator Q25. To obtain a p-type germanium semiconductor, it must be doped with [1997] (a) arsenic antimony indium phosphorus Q26. (a) D A B C Q30. [1998] (a) NOR XOR NAND OR [1997] (a) XOR OR AND NAND [1998] Q27. A semi-conducting 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-n junction an intrinsic semi-conductor a p-type semi-conductor an n-type semi-conductor Q31. The cause of the potential barrier in a p-n diode is [1998] (a) depletion of positive charges near the junction concentration of positive charges near the junction depletion of negative charges near the junction concentration of positive and negative charges near the junction Q32. Q28. (a) Q29. [1999] (a) OR gate XOR gate AND gate NAND gate Q33. In forward bias, the width of potential barrier in a p-n junction diode [1999]

4 (a) increases decreases remains constant first 1 then 2 Q34. A depletion layer consists of [1999] (a) electrons protons mobile ions immobile ions Q35. Which of the following when added acts as an impurity into silicon produced n-type semiconductor? [1999] (a) P Al B Mg Q36. In a junction diode, the holes are due to [1999] (a) protons extra electrons neutrons missing electrons Q37. Q39. The forward biased diode is [2000] (a) Q40. (a) XOR NOT NAND AND [2001] (a) AND NOR OR NAND Q38. [2000] (a) [2000] Q41. The intrinsic semiconductor becomes an insulator at [2001] (a) 0 C 0 K 300 K 100 C Q42. For a common emitter circuit if0.98 CEIIthen current gain for common emitter circuit will be [2001] (a) Q43. Transmission of light in optical fibre is due to [2001] (a) scattering diffraction polarisation multiple total internal reflections Q44.

Q49. Barrier potential of a p-n junction diode does not depend on [2003] (a) doping density diode design temperature forward bias (a) 2V when diode is forward biased Zero when diode is forward biased

5 Q49. Barrier potential of a p-n junction diode does not depend on [2003] (a) doping density diode design temperature forward bias (a) 2V when diode is forward biased Zero when diode is forward biased V when diode is reverse biased V when diode is forward biased [2002] Q45. In a p-n junction [2002] (a) The potential of the p and n-sides becomes higher alternately The p-side is at higher electrical potential than the n side The n-side is at higher electrical potential than the p- side Both the p and n-sides are at the same potential Q46. [2002] (a) Q47. If a full wave rectifier circuit is operating from 50Hz mains, the fundamental frequency in the ripple will be [2003] (a) 100 Hz 25 Hz 50 Hz 70.7 Hz Q48. An n-p-n transistor conducts when [2003] (a) both collector and emitter are negative with respect to the base both collector and emitter are positive with respect to the base collector is positive and emitter is negative with respect to the base collector is positive and emitter is at same potential as the base Q50. [2003] (a) XOR gate AND gate NAND gate OR gate Q51. Reverse bias applied to a junction diode [2003] (a) increases the minority carrier current lowers the potential barrier raises the potential barrier increases the majority carrier current Q52. In semiconductors, at room temperature [2004] (a) the conduction band is completely empty the valence band is partially empty and the conduction band is partially filled the valence band is completely filled and the conduction band is partially filled the valence band is completely filled Q53. 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 the output voltage is [2004] (a) 20/πV 10/πV 10V Q54. The output of OR gate is 1 [2004] (a) if either input is zero if both inputs are zero

6 if either or both inputs are 1 only if both inputs are 1 Q55. In a p-n junction photocell, the value of the photoelectromotive force produced by monochromatic light is proportional to [2004] (a) the voltage applied at the p-n junction the barrier voltage at the p-n junction the intensity of the light falling on the cell the frequency of the light falling on the cell Q56. Of the diodes shown in following diagrams, which one is reverse biased? [2004] Q59. Application of a forward bias to a p n junction (a) widens the depletion zone [2005] increases the potential difference across the depletion zone increases the number of donors on the n side increases the electric field in the depletion zone Q60. Zener diode is used for [2005] (a) amplification rectification stabilisation producing oscillations in an oscillator Q61. (a) Q57. Choose the only false statement from the following [2005] (a) In conductors, the valence and conduction bands may overlap Substances with energy gap of the order of 10 ev are insulators The resistivity of a semiconductor increases with increase in temperature The conductivity of a semiconductor increases with increase in temperature Q58. Carbon, silicon and germanium atoms have four valence electrons each. Their valence and conduction bands are separated by energy band gaps represented by (Eg )C, (Eg) Si and (Eg )Ge respectively. Which one of the following relationships is true in their case? [2005] (a) (Eg )C> (Eg) Si (Eg )C< (Eg) Si (Eg )C= (Eg) Si (Eg )C< (Eg )Ge [2006] (a) NAND gate NOR gate OR gate AND gate Q62. (a) Q63. A forward biased diode is [2006] [2006]

7 (a) Q64. The radius of germanium (Ge) nuclide is measured to be twice the radius of 9 4Be. The number of nucleons in Ge are [2006] (a) Q67. For a cubic crystal structure which one of the following relations indicating the cell characteristics is correct? [2007] (a) Q68. Q65. [2007] (a) Q66. [2007] (a) an insulator a metal an n-type semiconductor a p-type semiconductor Q69. The voltage gain of an amplifier with 9% negative feedback is 10. The voltage gain without feedback will be [2008] (a) Q70. 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 [2008] (a) Hz Hz Hz Hz Q71. (a) 1000 [2007]

8 [2008] (a) AND gate NAND gate NOR gate OR gate Q72. [2009] (a) (iv), (i), (iii) (iv), (ii), (i) (i), (iii), (iv) (iii), (iv), (ii) Q73. A p-n photodiode is fabricated from a semiconductor with a band gap of 2.5 ev. It can detect a signal of wavelength [2009] (a) 4000 nm 6000 nm Q74. particles emitted by it. The resulting daughter is an [2009] (a) isomer of parent isotone of parent isotope of parent isobar of parent Q76. Which one of the following statement is FALSE? [2010] (a) Pure Si doped with trivalent impurities gives a p-type semiconductor Majority carriers in a n-type semiconductor are holes Minority carriers in a p-type semiconductor are electrons The resistance of intrinsic semiconductor decreases with increase of temperature Q77. 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? [2010] (a) metallic bonding van der Waal's bonding ionic bonding covalent bonding Q78. The device that can act as a complete electronic circuit is [2010] (a) junction diode integrated circuit junction transistor zener diode Q79. (a) [2010] (a) [2009] Q75. The number of beta particles emitted by a radioactive substance is twice the number of alpha Q80. For transistor action: (1) Base, emitter and collector regions should have similar size and doping concentrations.

9 (2) The base region must be very thin and lightly doped. (3) The eimtter-base junction is forward biased and base-collector junction is reverse based. (4) Both the emitter-base junction as well as the basecollector junction are forward biased. (a) (3), (4) (4), (1) (1), (2) (2), (3) (a) the positive terminal of the battery is connected to p side and the depletion region becomes thick the positive terminal of the battery is connected to n side and the depletion region becomes thin the positive terminal of the battery is connected to n side and the depletion region becomes thick the positive terminal of the battery is connected to p side and the depletion region becomes thin Q1. Q81. Q2. Q3. Q4. Q5. Q6. (a) NAND gate NOR gate OR gate AND gate Q82. Q7. Q8. Q9. (a) [2011] Q10. Q11. Q83. In forward biasing of the p n junction [2011]

10 Q12. Q13. Q23. Q24. Q14. Q15. Q25. Q16. Q26. Q17. Q27. Q18. Q19. Q28. Q29. Q20. Q21. Q30. Q22.

11 Q31. Q40. Q32. Q41. Q42. Q33. Q43. Q44. Q34. Q45. Q35. Q46. Q36. Q37. Q38. Q47. Q48. Q39.

12 Q49. Q57. Q58. Q50. Q59. Q51. Q52. Q53. Q60. Q54. Q55. Q61. Q56.

13 Q67. Q62. Q68. Q63. Q69. Q64. Q70. Q65. Q71. Q66. Q72.

14 Q73. Q74. Q80. Q81. Q75. Q76. Q82. Q77. Q78. Q83. Q79.

Downloaded from

Downloaded from Question 14.1: In an n-type silicon, which of the following statement is true: (a) Electrons are majority carriers and trivalent atoms are the dopants. (b) Electrons are minority carriers and pentavalent