ELECTRONICS AND COMMUNICATION ENGINEERING ESE TOPICWISE OBJECTIVE SOLVED PAPER-I From (1991 018) Office : F-16, (Lower Basemet), Katwaria Sarai, New Delhi-110016 Phoe : 011-65064 Mobile : 81309090, 9711853908 E-mail: ifo@iesmasterublicatios.com, ifo@iesmaster.org Web : iesmasterublicatios.com, iesmaster.org
IES MASTER PUBLICATION F-16, (Lower Basemet), Katwaria Sarai, New Delhi-110016 Phoe : 011-65064, Mobile : 81309090, 9711853908 E-mail : ifo@iesmasterublicatios.com, ifo@iesmaster.org Web : iesmasterublicatios.com, iesmaster.org All rights reserved. Coyright 018, by IES MASTER Publicatios. No art of this booklet may be reroduced, or distributed i ay form or by ay meas, electroic, mechaical, hotocoyig, recordig, or otherwise or stored i a database or retrieval system without the rior ermissio of IES MASTER, New Delhi. Violates are liable to be legally rosecuted. First Editio : 017 Secod Editio : 018 Tyeset at : IES Master Publicatio, New Delhi-110016
PREFACE It is a immese leasure to reset toic wise revious years solved aer of Egieerig Services Exam. This booklet has come out after log observatio ad detailed iteractio with the studets rearig for Egieerig Services Exam ad icludes detailed exlaatio to all questios. The aroach has bee to rovide exlaatio i such a way that just by goig through the solutios, studets will be able to uderstad the basic cocets ad will aly these cocets i solvig other questios that might be asked i future exams. Egieerig Services Exam is a gateway to a immesly satisfyig ad high exosure job i egieerig sector. The exosure to challeges ad oortuities of leadig the diverse field of egieerig has bee the mai reaso for studets otig for this service as comared to others. To facilitate selectio ito these services, availability of arithmetic solutio to revious year aer is the eed of the day. Towards this ed this book becomes idisesable. Mr. Kacha Kumar Thakur Director IES Master
Note: Directio of all Assertio Reasoig (A R) tye of questios covered i this booklet is as follows: DIRECTIONS: The followig four items cosist of two statemets, oe labelled as Assertio A ad the other labelled as Reaso R. You are to examie these two statemets carefully ad select the aswer to these two statemets carefully ad select the aswer to these items usig the codes give below: (a) Both A ad R are idividually true ad R is the correct exlaatio of A (b) Both A ad R are idividually true but R is ot the correct exlaatio of A (c) A is true but R is false (d) A is false but R is true. Note: Directio of all Statemet-I ad Statemet-II tye of questios covered i this booklet is as follows: DIRECTION: Followig items cosists of two statemets, oe labelled as Statemet (I) ad the other as Statemet (II). You are to examie these two statemets carefully ad select the aswers to these items usig the code give below: (a) Both Statemet : (I) ad Statemet (II) are idividually true ad Statemet (II) is the correct exlaatio of Statemet (I). (b) Both Statemet (I) ad Statemet (II) are idividually true but Statemet (II) is ot the correct exlaatio of Statemet (I). (c) Statemet (I) is true but Statemet (II) is false (d) Statemet (I) is false but Statemet (II) is true.
CONTENTS 1. Basic Electroic Egieerig... 01 141. Materials ad Comoets... 14 49 3. Measuremet ad Istrumetatios... 50 37 4. Network Theory... 373 68 5. Aalog Electroics... 69 791 6. Digital Electroics... 79 941 7. Microrocessor... 94 989 8. Basic Electrical Egieerig... 990 1001
1 S YL L A BU S Basics of semicoductors; Diode/Trasistor basics ad characteristics; Diodes for differet uses; Juctio & Field Effect Trasistors (BJTs, JFETs, MOSFETs); Trasistor amlifiers of differet tyes, oscillators ad other circuits; Basics of Itegrated Circuits (ICs); Biolar, MOS ad CMOS ICs; Basics of liear ICs, oeratioal amlifiers ad their alicatios-liear/o-liear, Otical sources/ detectors; Basics of Oto electroics ad its alicatios. Cotets 1. Basic of Semicoductor ------------------------------------------------------------- 1 47. - Juctio Diode ad Oto Electroics ------------------------------------ 48 8 3. Biolar Juctio Trasistors (BJTs)----------------------------------------- 83 101 4. Field Effect Trasistors (FETs) --------------------------------------------- 10 1 5. Silico Cotrolled Rectifiers ------------------------------------------------- 13 13 6. Itegrated Circuits (ICs) ------------------------------------------------------ 133 141
1 IES 018 1. Silico devices ca be emloyed for a higher temerature limit (190 ºC to 00 ºC) as comared to germaium devices (85 ºC to 100 ºC). With resect to this, which of the followig are icorrect? 1. Higher resistivity of silico. Higher ga eergy of silioc 3. Lower itrisic cocetratio of silico 4. Use of silico devices i high-ower alicatios Select the correct aswer usig the code give below: (a) 1, ad 4 (b) 1, ad 3 (c) 1, 3 ad 4 (d), 3 ad 4. A samle of germaium is made -tye be additio of idium at the rate of oe idium atom for every.5 10 8 germaium atoms. Give, i =.5 10 19 /m 3 at 300 K ad the umber of germaium atoms er m 3 = 4.4 10 8. What is the value of? (a) 3.55 10 18 /m 3 (b) 3.76 10 18 /m 3 (c) 7.87 10 18 /m 3 (d) 9.94 10 18 /m 3 IES 016 3. The electrical coductivity of ure semicoductor is: (a) Proortioal to temerature (b) Icreases exoetially with temerature (c) Decreases exoetially with temerature (d) Not altered with temerature. 4. Which oe of the followig statemets is correct? (a) For isulators the bad-ga is arrow as comared to semicoductors (b) For isulators the bad-ga is relatively wide whereas for semicoductors it is arrow (c) The bad-ga is arrow i width for both the isulators ad coductors (d) The bad-ga is equally wide for both coductors ad semicoductors. 5. I a extrisic semicoductor the coductivity sigificatly deeds uo: (a) Majority charge carriers geerated due to doig (b) Miority charge carriers geerated due to thermal agitatio (c) Majority charge carriers geerated due to thermal agitatio (d) Miority charge carriers geerated due to imurity doig. 6. A Ge samle at room temerature has itrisic carrier cocetratio, i = 1.5 10 13 cm 3 ad is uiformly doed with accetor of 3 10 16 cm 3 ad door of.5 10 15 cm 3. The, the miority charge carrier cocetratio is: (a) 0.918 10 10 cm 3 (b) 0.818 10 10 cm 3
Basic Electroic Egieerig 3 (c) 0.918 10 1 cm 3 (d) 0.818 10 1 cm 3 7. Assume that the values of mobility of holes ad that of electros i a itrisic semicoductor are equal ad the values of coductivity ad itrisic electro desity are.3 / m ad.5 10 19 /m 3 resectively. The, the mobility of electro/hole is aroximately: (a) 0.3 m /Vs (c) 0.7 m /Vs (b) 0.5 m /Vs (d) 0.9 m /Vs 8. A silico samle A is doed with 10 18 atom/ cm 3 of Boro ad aother silico samle B of idetical dimesios is doed with 10 18 atom/ cm 3 of Phoshorous. If the ratio of electro to hole mobility is 3, the the ratio of coductivity of the samle A to that of B is: (a) (c) 3 1 3 9. The Hall-coefficiet of a secime of doed semicoductor is 3.06 10 4 m 3 C 1 ad the resistivity of the secime is 6.93 10 3 m. The majority carrier mobility will be: (a) 0.014 m V 1 s 1 (b) 0.04 m V 1 s 1 (c) 0.034 m V 1 s 1 (d) 0.044 m V 1 s 1 10. Doed silico has Hall-coefficiet of 3.68 10 4 m 3 C 1 ad the its carrier cocetratio value is: (b) (d) (a).0 10 m 3 (b).0 10 m 3 (c) 0. 10 m 3 (d) 0. 10 m 3 11. The ositio of the itrisic Fermi level of a udoed semicoductor (E Fi ) is give by: (a) (b) E E kt N l N C V V E E kt N l N C C V V C 3 1 (c) (d) E E kt N l N C V V E E kt N l N C C V V C IES 015 1. The radius of the first Bohr orbit of electros i hydroge atom is 0.59 Å. What is the radius of the secod Bohr orbit i sigly ioized helium atom? (a) 1.058 Å (c) 10.58 Å (b) 0.64 Å (d) 0.064 Å 13. For which oe of the followig materials, is the Hall coefficiet closest to zero? (a) Metal (b) Isulator (c) Itrisic semicoductor (d) Alloy 14. At temerature of 98 Kelvi, Silico is ot suitable for most electroic alicatios, due to small amout of coductivity. This ca be altered by (a) Getterig (c) Squeezig (b) Doig (d) Siterig 15. The eergy ga i the eergy bad structure of a material is 9 ev at room temerature. The material is (a) Semicoductor (c) Metal (b) Coductor (d) Isulator 16. By doig Germaium with Gallium, the tyes of semicoductors formed are : 1. N tye. P tye 3. Itrisic 4. Extrisic Which of the above are correct? (a) 1 ad 4 (b) ad 4 (c) 1 ad 3 (d) ad 3 17. A -tye of silico ca be formed by addig imurity of : 1. Phoshorous. Arseic
Basic Electroic Egieerig 1 ANSWER KEY 1. (b) 6. (b) 51. (b) 76. (a) 101. (d) 16. (c). (a) 7. (b) 5. (a) 77. (b) 10. (a) 17. (d) 3. (b) 8. (c) 53. (b) 78. (a) 103. (d) 18. (b) 4. (b) 9. (b) 54. (c) 79. (d) 104. (b) 19. (c) 5. (a) 30. (d) 55. (d) 80. (d) 105. (a) 130. (c) 6. (b) 31. (c) 56. (c) 81. (d) 106. (c) 131. (c) 7. (a) 3. (b) 57. (b) 8. (b) 107. (b) 13. (b) 8. (c) 33. (b) 58. (d) 83. (d) 108. (c,d) 133. (b) 9. (d) 34. (a) 59. (a) 84. (c) 109. (c) 134. (a) 10. (a) 35. (b) 60. (c) 85. (d) 110. (b) 135. (a) 11. (c) 36. (a) 61. (c) 86. (d) 111. (b) 136. (a) 1. (a) 37. (d) 6. (b) 87. (b) 11. (b) 137. (c) 13. (a) 38. (d) 63. (b) 88. (c) 113. (d) 138. (a) 14. (b) 39. (c) 64. (a) 89. (d) 114. (d) 139. (c) 15. (d) 40. (a) 65. (d) 90. (c) 115. (d) 140. (a) 16. (b) 41. (a) 66. (c) 91. (c) 116. (d) 141. (a) 17. (a) 4. (b) 67. (b) 9. (b) 117. (b) 14. (d) 18. (b) 43. (b) 68. (b) 93. (b) 118. (b) 143. (c) 19. (d) 44. (d) 69. (d) 94. (c) 119. (a) 144. (a) 0. (c) 45. (b) 70. (c) 95. (d) 10. (a) 145. (d) 1. (c) 46. (a) 71. (c) 96. (c) 11. (b) 146. (b). (b) 47. (b) 7. (b) 97. (a) 1. (b) 147. (d) 3. (a) 48. (b) 73. (c) 98. (d) 13. (d) 148. (c) 4. (a) 49. (b) 74. (a) 99. (d) 14. (b, c) 149. (b) 5. (a) 50. (b) 75. (b) 100. (d) 15. (a) 150. (c)
ESE Toicwise Objective Solved Paer-I 1991-018 Sol 1: Sol : Sol 3. (b) Whe silico devices ca be emloyed for higher temerature limit (190 C to 00 C) whe comared to germaium devices (85 C to 100 C) imlies that silico devices ca be used i high-ower alicatios as they suort flow of high amouts of currets. That is statemet- 4 is true therefore statemets 1,, 3 are icorrect as er otios. (a) Give that 1 idium atom is doed for every.5 10 8 Ge atom itrisic carrier cocetratio ( i ) =.5 10 19 /m umber of germaium atoms = 4.4 10 8 1.5 10 8? 4.4 10 8 Cocetratio of -tye imurities We kow = (N A ) ( ) = 4.4 10.5 10 8 = 1.76 10 0 atom i (1.76 10 0 ) ( ) = (.5 10 19 ) (b) ( ) = 8 38.5 10 1.76 10 0 = 3.551 10 18 /m 3 I a ure semicoductor the o of holes ad electros are equal ad is give by where = = i = o of electros = o of holes Sol 4. Sol 5. Sol 6. i = itrisic carrier cocetratio If the temerature of semicoductor icreases, the cocetratio of charge carriers (electros ad holes) is also icreased. Hece the coductivity of a semicoductor is icreased accordigly. The relatio betwee temerature ad cocetratio of charge carriers i ure semicoductor is give as = A T3e EG0/KT i 0 where T is the temerature i Kelvi scale. (b) For isulators, the eergy bad-ga is greater tha 6 ev, whereas for semicoductors, the eergy bad ga is aroximately equal to 1 ev. Thus, for isulators, the bad-ga is relatively wide, whereas for semicoductors, it is arrow. (a) I a extrisic semicoductor, Majority carrier cocetratio Miority carrier cocetratio Extrisic Semicodcutor -tye -tye = NA = N i N Codutivity q q qn A A D i N D q q qn D Thus, coductivity of a extrisic semicoductor sigificatly deeds uo majority charge carrier, geerated due to imurity doig. (b) Give, N a = 3 10 16 / cm3
Basic Electroic Egieerig 3 Sol 7. Sol 8. ad N d =.5 10 15 / cm3 Sice, N a > N d, semicoductor is of - tye. Majority carrier (hole) cocetratio, = N a Nd =.75 10 16 / cm3 Miority carrier (electro) cocetratio, (a) = Give, = 1.5 10 13 = / cm.75 10 i 3 16 = 0.818 10 10 / cm3 i =.3/ m i =.5 10 19 / cm3 Coductivity, = iq + iq = = i = iq i = i ad = i q.3.5 10 1.6 10 i 19 19 = 0.9 m V s m V s = = 0.9m V s 0.3 m V s (c) Give, 18 3 A = 10 / cm ad 18 3 B = 10 / cm = 3 Coductivity of samle A, A = Aq Coductivity of samle B, B = Bq Thus, A B A B = = 1 3 q A q B Sol 9. Sol 10. Sol 11. (d) Give, R = 3.06 10 m C H ad 4 3 1 3 6.93 10 m 1 R Resistivity, H Sol 1. (a) 4 RH 3.06 10 0.044 m V s 3 6.93 10 (a) Give, R H = 4 3 1 3.68 10 m C Hall Coefficiet, R H = = 1 R q H 1 1 q v = 4 19 1 3.68 10 1.6 10 3 = 1.7 10 / m 3 10 / m (c) Itrisic electro cocetratio, i EC EFi = NC ex kt Itrisic hole cocetratio, i EFi EV = N V ex kt For a itrisic Semicoductor, i = i EC EFi EFi EV NC ex NV ex kt kt E Fi = EC EV kt N V l NC Radius of Bohr s orbit of Hydroge ad Hydroge like secies is calculated as r = h 1, 4 me Z