Title

: UPSC ESE 2022 : Electronics & Telecommunication Engineering Chapter Wise & Year Wise Solved Papers 2000-2021

Language

: English

Editor’s Name : Vinit Garg Copyright ©

: 2021 CLIP

No part of this book may be reproduced in a retrieval system or transmitted, in any form or by any means, electronics, mechanical, photocopying, recording, scanning and or without the written permission of the Author/Publisher. Typeset & Published by : Career Launcher Infrastructure (P) Ltd. A-45, Mohan Cooperative Industrial Area, Near Mohan Estate Metro Station, New Delhi - 110044 Marketed by : G.K. Publications (P) Ltd. Plot No. 9A, Sector-27A, Mathura Road, Faridabad, Haryana-121003 ISBN : 978-93-91061-95-1 Printer’s Details : Made in India, New Delhi. For product information : Visit www.gkpublications.com or email to [email protected]

Engineering Services Examination (ESE) is a combined three-stage examination conducted by the UPSC for recruitment to Indian Engineering Services (IES). Every year a large number of candidates appear for this exam, competing for a limited number of posts. Thus ESE is considered as one of the toughest exam in India due to its low selection ratio and technical nature. Unlike before, the ESE 2017 pattern and syllabus has been completely changed. The old pattern consisted of three stages wherein the candidates were allowed to attempt all the stages. But the revised pattern includes three stages - prelims, mains and personality test, the candidate is required to qualify each stage in order to move on to the next stage. The prelims stage includes two papers – paper 1 for general studies & engineering aptitude and paper 2 for technical ability, in which both papers are objective type. Here the paper 1 is common for all the branches, whereas paper 2 is based on the candidate’s respective discipline. The second stage - mains is again divided into two papers wherein both are conventional type to test the technical ability of respective engineering discipline. GK Publications has been the ‘‘publisher of choice’’ to students preparing for GATE, ESE and other technical test prep examinations in the country. GKP's ESE 2021 series provides a wide range of study material which is classified into 13 books, with 5 guides, 4 objective paper books and 4 conventional paper books to simplify the entire preparation. These books have been thoroughly updated as per the latest pattern and syllabus to provide everything you need to perfect your score. GKP has also launched an android app to provide you an update on all upcoming vacancies in the technical segment and it also has a lot of added content to aid your preparation. We hope this little effort of ours will be helpful in achieving your dreams. If you have any suggestions on improvement of this book, you can write to us at [email protected]. All the Best! Team GKP

 Syllabus  Exam Pattern

Solved Papers P aper I 1. Basic Electronics Engineering

1.1-1.48

– Questions

1.1

– Answers

1.37

– Explanations

1.38

2. Materials Science

2.1-2.32

– Questions

2.1

– Answers

2.25

– Explanations

2.26

3. Electronic Measurements and Instrumentation – Questions

3.1-3.34 3.1

– Answers

3.29

– Explanations

3.29

4. Network Theory

4.1-4.74

– Questions

4.1

– Answers

4.43

– Explanations

4.44

5. Analog and Digital Circuits

5.1-5.92

– Questions

5.1

– Answers

5.71

– Explanations

5.73

Paper II 6. Analog and Digital Communication Systems – Questions

6.1-6.32 6.1

– Answers

6.24

– Explanations

6.25

7. Control System – Questions

7.1

– Answers

7.36

– Explanations

7.37

8. Computer Organization and Architecture – Questions

8.1-8.32 8.1

– Answers

8.29

– Explanations

8.30

9. Electro Magnetics – Questions

9.1-9.50 9.1

– Answers

9.36

– Explanations

9.37

10. Advanced Communication Topics – Questions



7.1-7.44

10.1-10.38 10.1

– Answers

10.32

– Explanations

10.33

Solved Paper 2016 – Objective Paper I

1-22

– Objective Paper II

1-20



Solved Paper 2017

1-31



Solved Paper 2018

1-24



Solved Paper 2019

1-241-31



Solved Paper 2020

1-28



Solved Paper 2021

1-23

PAPER - I 1. Basic Electronics Engineering : Basics of semiconductors; Diode/Transistor basics and characteristics; Diodes for different uses; Junction & Field Effect Transistors (BJTs, JFETs, MOSFETs); Transistor amplifiers of different types, oscillators and other circuits; Basics of Integrated Circuits (ICs); Bipolar, MOS and CMOS ICs; Basics of linear ICs, operational amplifiers and their applications-linear/non-linear; Optical sources/ detectors; Basics of Opto electronics and its applications. 2. Basic Electrical Engineering : DC circuits-Ohm's & Kirchoff 's laws, mesh and nodal analysis, circuit theorems; Electro-magnetism, Faraday's & Lenz's laws, induced EMF and its uses; Single-phase AC circuits; Transformers, efficiency; Basics- DC machines, induction machines, and synchronous machines; Electrical power sources- basics: hydroelectric, thermal, nuclear, wind, solar; Basics of batteries and their uses. 3. Materials Science : Electrical Engineering materials; Crystal structure & defects; Ceramic materialsstructures, composites, processing and uses; Insulating laminates for electronics, structures, properties and uses; Magnetic materials, basics, classification, ferrites, ferro/para-magnetic materials and components; Nano materials-basics, preparation, purification, sintering, nano particles and uses; Nano-optical/magnetic/ electronic materials and uses; Superconductivity, uses. 4. Electronic Measurements and Instrumentation : Principles of measurement, accuracy, precision and standards; Analog and Digital systems for measurement, measuring instruments for different applications; Static/dynamic characteristics of measurement systems, errors, statistical analysis and curve fitting; Measurement systems for non-electrical quantities; Basics of telemetry; Different types of transducers and displays; Data acquisition system basics. 5. Network Theory : Network graphs & matrices; Wye-Delta transformation; Linear constant coefficient differential equations- time domain analysis of RLC circuits; Solution of network equations using Laplace transforms- frequency domain analysis of RLC circuits; 2-port network parameters-driving point & transfer functions; State equations for networks; Steady state sinusoidal analysis. 6. Analog and Digital Circuits : Small signal equivalent circuits of diodes, BJTS and FETs; Diode circuits for different uses; Biasing & stability of BJT & JFET amplifier circuits; Analysis/design of amplifiersingle/multi-stage; Feedback& uses; Active filters, timers, multipliers, wave shaping, A/D-D/A converters; Boolean Algebra& uses; Logic gates, Digital iC families, Combinatorial/sequential circuits; Basics of multiplexers, counters/registers/ memories /microprocessors, design & applications.

PAPER - II 1. Analog and Digital Communication Systems: Random signals, noise, probability theory, information theory; Analog versus digital communication & applications: Systems- AM, FM, transmitters/receivers, theory/practice/ standards, SNR comparison; Digital communication basics: Sampling, quantizing, coding, PCM, DPCM, multiplexing-audio/video; Digital modulation: ASK, FSK, PSK; Multiple access: TDMA, FDMA, CDMA; Optical communication: fibre optics, theory, practice/standards. 2. Control Systems: Classification of signals and systems; Application of signal and system theory; System realization; Transforms & their applications; Signal flow graphs, Routh-Hurwitz criteria, root loci, Nyquist/Bode plots; Feedback systems-open & close loop types, stability analysis, steady state, transient and frequency response analysis; Design of control systems, compensators, elements of lead/lag compensation, PID and industrial controllers.

3. Computer Organization and Architecture: Basic architecture, CPU, I/O organisation, memory organisation, peripheral devices, trends; Hardware /software issues; Data representation & Programming; Operating systems-basics, processes, characteristics, applications; Memory management, virtual memory, file systems, protection & security; Data bases, different types, characteristics and design; Transactions and concurrency control; Elements of programming languages, typical examples. 4. Electro Magnetics: Elements of vector calculus, Maxwell's equations-basic concepts; Gauss', Stokes' theorems; Wave propagation through different media; Transmission Lines-different types, basics, Smith's chart, impedance matching/transformation, S-parameters, pulse excitation, uses; Waveguides-basics, rectangular types, modes, cut-off frequency, dispersion, dielectric types; Antennas-radiation pattern, monopoles/dipoles, gain, arrays-active/passive, theory, uses. 5. Advanced Electronics Topics: VLSI technology: Processing, lithography, interconnects, packaging, testing; VLSI design: Principles, MUX/ROM/PLA-based design, Moore & Mealy circuit design; Pipeline concepts & functions; Design for testability, examples; DSP: Discrete time signals/systems, uses; Digital filters: FIR/IIR types, design, speech/audio/radar signal processing uses; Microprocessors & microcontrollers, basics, interrupts, DMA, instruction sets, interfacing; Controllers & uses; Embedded systems. 6. Advanced Communication Topics: Communication networks: Principles /practices /technologies /uses /OSI model/security; Basic packet multiplexed streams/scheduling; Cellular networks, types, analysis, protocols (TCP/TCPIP); Microwave & satellite communication: Terrestrial/space type LOS systems, block schematics link calculations, system design; Communication satellites, orbits, characteristics, systems, uses; Fibre-optic communication systems, block schematics, link calculations, system design.

Stage-I

Objective Type Papers (Preliminary/Stage-I)

Marks

Time

Paper-I

General Studies and Engineering Aptitude Paper

200

2 hours

Paper-II

Engineering Discipline Specific Paper

300

3 hours

Sub-Total

500

Basic Electronics Engineering

1

C HAPTER

1.1

Basic Electronics Engineering

2015 1. At temperature of 298 Kelvin, Silicon is not suitable for most-electronic applications, due to small amount of conductivity. This can be altered by (a) Gettering

(b) Doping

(c) Squeezing

(d) Sintering

2. By doping Germanium with Gallium, the types of semi-conductors formed are: 1. N type

2. P type

3. Intrinsic

4. Extrinsic

Which of the above are correct? (a) 1 and 4

(b) 2 and 4

(c) 1 and 3

(d) 2 and 3

3. An n-type of silicon can be formed by adding impurity of :

(c) Forward biased and the thickness of the depletion layer increases till I-region becomes free of mobile carriers (d) Reverse biased and the thickness of the depletion layer decreases till I-region becomes free of mobile carriers 6. The number of holes in an N-type silicon with intrinsic value 1.5 × 10 10 /cm 3 and doping concentration of 1017/cm3, by using mass-action law is (a) 6.67 × 106/cc (b) 4.44 × 10–25/cc (c) 1.5 × 10–24/cc (d) 2.25 × 103/cc 7. A tunnel-diode is best suited for

1. Phosphorous

(a) Very low frequencies

2. Arsenic

(b) 50 Hz

3. Boron

(c) 100 kHz

4. Aluminium

(d) Microwave frequencies

Which of the above are correct? (a) 1 and 2

(b) 2 and 3

(c) 3 and 4

(d) 1 and 4

4. According to Einstein’s relationship for a semiconductor, the ratio of diffusion constant to the mobility of the charge carriers is

8. Small recovery time of a diode is most significant for (a) Line-frequency rectification (b) Switching operations (c) High- frequency rectification and switching operations

(a) Variable and is twice the volt equivalent of the temperature

(d) Low-frequency rectification and switching operations

(b) Constant and is equal to the volt equivalent of the temperature

9. In JFET, when operated above the pinch-off voltage, the

(c) Equal to two and is twice the volt equivalent of the temperature

(a) Depletion region becomes smaller

(d) Equal to one and is equal to the volt equivalent of the temperature

(c) Drain current remains practically constant

5. Swept-out voltage in PIN diode happens when PIN diode is (a) Forward biased and the thickness of the depletion layer decreases till I-region becomes free of mobile carriers (b) Reverse biased and the thickness of the depletion layer increases till I-region becomes free of mobile carriers

(b) Drain current starts decreasing (d) Drain current increases steeply 10. Thermal runaway is not possible in FET because, as the temperature of FET increases (a) The drain current increases (b) The mobility of charge carriers decreases (c) The mobility of charge carriers increases (d) The transconductance increases

1.2

Basic Electronics Engineering

11. Consider the following statements regarding an N-P-N Bipolar Junction Transistor:

17. A CMOS amplifier when compared to an N channel MOSFET has the advantage of

1. Emitter diode is forward biased and collector diode is reverse biased

(a) Higher cutoff frequency

2. Emitter has many free electrons

(c) Higher current gain

3. Free electrons are injected into base and pass through collector

(d) Lower power dissipation

4. Depletion layers around junction J1 and J2 of BJT are widened. Which of the above statements are correct? (a) 1, 2 and 4

(b) 1, 3 and 4

(c) 2, 3 and 4

(d) 1, 2 and 3

12. A freewheeling diode in a phase controlled rectifier (a) improves the line power factor (b) enables inverse operation (c) is responsible for additional reactive power (d) is responsible for additional harmonics 13. The zeners incorporated within the encapsulations of some MOSFETs are meant for (a) Reducing the cost (b) Biasing the gate circuit (c) Self-protecting the device against transients (d) None of the above 14. When UJT is used for triggering an SCR, the waveshape of the signal obtained from UJT circuit is (a) Sine wave (b) Saw tooth wave

(b) Higher voltage gain

18. Consider the following statements regarding optocouplers: 1. Optocouplers are LEDs driving photodiodes in a single package to provide electrical isolation between input and output 2. Optocoupler is LED driving a phototransistor in a single package that replaces pulse transformers working at input zero crossing 3. Optocouplers are used as temporary non fixed joints between optical fibre terminations Which of the above statements are correct ? (a) 1, 2 and 3 (b) 1 and 2 only (c) 1 and 3 only (d) 2 and 3 only 19. Which of the following does not cause permanent damage to an SCR ? (a) High current (b) High rate of rise of current (c) High temperature rise (d) High rate of rise of voltage . 20. The basic structure of an avalanche photodiode is

(c) Trapezoidal wave

(a) p+ – i – p – n+

(b) p+ – i – n+

(d) Square wave

(c) p+ – p– – n+

(d) i – p– – n+

15. Darlington pairs are frequently used in linear ICs because, they (a) Do not require any capacitors or inductors (b) Have enormous impedance transformation capability (c) Can be readily formed/hooked from two adjacent transistors (d) Resemble emitter follower 16. In a MOS capacitance fabricated on a P-type semiconductor, strong inversion occurs, when potential is (a) Equal to Fermi level

21. In a pn junction diode, (a) 2.3 mV/°C (c) 10.0 mV/°C

dV is equal to dT (b) 3.5 mV/°C

(d) 12.5 mV/°C

22. Examples of an active display and a passive display respectively are (a) LCD and Gas discharge plasma (b) LED and LCD (c) Gas discharge plasma and LED (d) Electrophoretic Image display and LED 23. The dc resistivity and permeability exhibited by a type 1 superconductor are respectively

(b) Zero

(a) Zero and zero

(c) Negative and equal to Fermi potential in magnitude

(b) Zero and unity

(d) Positive and equal to Fermi potential in magnitude

(d) Unity and Unity

(c) Unity and zero

Basic Electronics Engineering

Directions(Q.24–27) : Each of the next Fourteen (14) items consists of two statements, one labelled as the ‘Statement (I)’ and the other as ‘Statement (II)’. Examine these two statements carefully and select the answers to these items using the codes given below : Codes:

1.3

29. An LTI system has a wide-sense stationary (WSS) input signal with zero mean. Its output is (a) non-zero mean and non-WSS signal (b) zero mean and WSS signal (c) non-zero mean and WSS signal (d) zero mean and non-WSS signal

(a) Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I)

30. In degenerately doped n-type semiconductor, the Fermi level lies in conduction band when

(b) Both Statement (I) and Statement (II) are individually true but Statement (II) is NOT the correct explanation of Statement (I)

(a) concentration of electrons in the conduction band exceeds the density of states in the valence band

(c) Statement (I) is true but Statement (II) is false

(b) concentration of electrons in the valence band exceeds the density of states in the conduction band

(d) Statement (I) is false but Statement (II) is true 24. Statement (I) : One of the mechanisms by which a transistor’s usefulness may be terminated, as the collector voltage is increased, is called punch through. Statement (II) : Punch through results from the increased width of the collector-junction transition region with increased collectorjunction voltage. 25. Statement (I) : Conduction takes place in an enhancement MOSFET only for gate voltages below the threshold level. Statement (II) : In an enhancement MOSFET, a channel of semiconductor of the same type as the source and drain is induced in the substrate by a positive voltage applied to the gate. 26. Statement (I) : MOSFET is a field effect transistor whose drain current is controlled by the voltage applied at the gate. Statement (II) : MOSFET is an insulated gate FET. 27. Statement (I) : All passive components can be fabricated in a single chip. Statement (II) : As opposed to discrete circuits where all components are separately inserted and connected, in an integrated circuit, they are simultaneously created on a chip of semiconductor material during manufacturing.

2014 28. What is an advantage of MOS transistor structure in integrated circuits ?

(c) concentration of electrons in the conduction band exceeds the product of the density of states in the valence band and conduction band (d) None of the above 31. The purpose of connecting a Zener diode in a UJT circuit, used for triggering thyristors, is to (a) expedite the generation of triggering pulses (b) delay the generation of triggering pulses (c) provide a constant voltage to UJT to prevent erratic firing (d) provide a variable voltage to UJT as the source voltage changes Directions (Q. 32 - 35) : Each of the following items consists of two statements, one labelled as ‘Statement (I)' and the other as ‘Statement (II)'. Examine these two statements carefully and select the answers to these items using the code given below. Code : (a) Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I) (b) Both Statement (I) and Statement (II) are individually true but Statement (II) is not the correct explanation of Statement (I) (c) Statement (I) is true but Statement (II) is false (d) Statement (I) is false but Statement (II) is true 32. Statement (I) :

(a) Faster switching

With a small additional energy, usually thermal, the valence electrons in germanium can become free electrons.

(b) Less capacitance

Statement (II) :

(c) Higher component density and lower cost

The valence electrons in germanium are in the fourth orbit and are at high energy level.

(d) Lower resistance

1.4

Basic Electronics Engineering

33. Statement (I) : An FET is a current-controlled device. Statement (II) : Operation of an FET depends only on majority carriers. 34. Statement (I) : Thermal runaway is not possible in an FET.

41. What is the biasing condition of junctions in bipolar junction transistor to work as an amplifier? (a) Reverse biased base to emitter junction and reverse biased base to collector junction (b) Forward biased base to emitter junction and reverse biased base to collector junction

Statement (II) :

(c) Forward biased base to emitter junction and forward biased base to collector junction

As the temperature of FET increases, the mobility of carriers decreases.

(d) Reverse biased base to emitter junction and forward biased base to collector junction

35. Statement (I) :

42. In a JFET, operating above pinch-off voltage, the

In an enhancement type MOSFET (with n-type source and drain regions), only positive voltage can be applied to the gate with respect to the substrate (p-type).

(a) drain current increases steeply (b) drain current remains practically constant (c) drain current starts decreasing (d) depletion region reduces

Statement (II) : Only with a positive voltage to the gate, an ‘inversion layer' is formed and conduction can take place. 36. If an input signal ranges from 20A – 40A with an output signal ranging from 0.5 mA – 1.5 mA, what is the  a.c.? (a) 0.05

(b) 20

(c) 50

(d) 500

37. The best device for improving the switching speeds of bipolar transistors is (a) speed-up capacitor (b) transistor with higher cut-off frequency

43. If VCC = 18V, voltage divider resistances R1 = 4.7 k and R2 = 1500 , what is the base bias voltage ? (a) 8.70 V

(b) 4.35 V

(c) 2.90 V

(d) 0.70 V

44. An SCR has an anode supply of sine voltage 200Vr.m.s., 50 Hz applied through a 100  resistor and fired at an angle of 60. Assuming no voltage drop, the r.m.s. value of the output voltage is nearly (a) 90 V

(b) 126 V

(c) 166 V

(d) 200 V

45. In a GTO, anode current begins to fall when gate current

(c) clamping diode

(a) is negative peak at time t = 0

(d) clamping diode with zero storage time

(b) is negative peak at time t = storage period

38. The early effect in bipolar junction transistor is caused by (a) fast turn-off

(c) just begins to become negative at t = 0 (d) just begins to become positive at t = 0 46. An SCR is turned off when its turn-off time is

(b) fast turn-on

(a) less than the circuit time constant

(c) large emitter to base forward bias

(b) greater than the circuit time constant

(d) large collector to base reverse bias

(c) less than the circuit turn-off time

39. To get higher cut-off frequency in a BJT, base sheet resistance should be (a) low (b) high (c) equal to cut-off frequency (d) zero 40. A BJT operates as a switch (a) in the active region of transfer characteristics (b) with no signal condition (c) under small signal conditions (d) under large signal conditions

(d) greater than the circuit turn-off time

2013 47. The bandwidth of a digitally recorded signal primarily depends upon (a) the physical properties of the components processing the signal

system

(b) the frequency at which the signal is sampled (c) the frequency of the clock signal that is used to encode binary values responding the signal (d) the frequency of the noise affecting signal quality

Basic Electronics Engineering

48. While measuring the voltage developed by a thermocouple, it is found that there is always an offset voltage. This is due to (a) a voltae across a thermocouple even at very low temperature (b) some photoelectric voltage across the junction due to ambient light (c) a barrier potential across the junction (d) an additional thermocouple is formed due to the connecting wires and one of the metals. 49. For an antenna, Rediation Intensity is defined as (a) the time-averaged rediated power per unit solid angle (b) the peak rediated power per unit solid angle (c) the peak radiated power per unit area (d) the time-averaged radiated power per unit area 50. A source of (power/energy) feeds the input port of an amplifier and the output port is connected to a ‘load’. The input impedance of the ideal amplifier should ideally be (a) zero

(b) 

(c) low

(d) high

51. Medium doping in Silicon and Germanium corresponds to impurity of the order of (a) 1 part in 106

(b) 1 part in 105

(c) 1 part in 104

(d) 1 part in 108

52. An electric field is applied to a semiconductor. Let the number of charge carrier be n and the average drift speed be v. If the temperature is increased then (a) both n and v will increase (b) n will increase but v will decrease (c) v will increase but n will decrease (d) both n and v will decrease Directions : Each of the next Five (5) items consists of two statements, one labelled as the ‘Statement (I)’ and the other as ‘Statement (II)’. You are to examine these two statements carefully and select the answers to these items using the codes given below: Code: (a) Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I) (b) Both Statement (I) and Statement (II) are individually true but Statement (II) is NOT the correct explanation of Statement (I) (c) Statement (I) is true but Statement (II) is false. (d) Statement (I) is false but Statement (II) is true.

1.5

53. Statement I : Centre tap transformer is essential for a centre-tapped rectifier. Statement II : In half wave rectification minimum two diodes are required. 54. Statement I : Power factor is a measure of the power flow in the insulator and should be low. Statement II : It varies with the temperature and usually increases with the rise in temperature of the insulation. 55. Statement I : An SCR has a current controlled negative resistance characteristic. Statement II : For a given current the voltage can be determined while for a given voltage current cannot be determined. 56. Statement I : JEET is operated in depletion mode only. Statement II : The input resistance of a MOSFET is several orders of magnitude greater than that of a JEET. 57. Statement I : A photodiode is an example of a photo-conductive sensor. Statement II : A photodiode can be used as either a photo conductive or a photo resistive sensor. 58. A heavily doped semiconductor has (a) a resistivity which decreases expo-nentially with temperature (b) a resistivity which rises almost linearly with temperature (c) a negative temperature coefficient of resistance (d) a positive temperature coefficient of resistance 59. A Zener diode has the following properties: 1. It is properly doped crystal diode with sharp breakdown 2. It is reverse biased 3. Its forward characteristics are just that of ordinary diode 4. Its reverse characteristics are like ordinary diode (a) 1, 2, 3 and 4 (b) 1, 2 and 4 only (c) 1, 2 and 3 only (d) 3 and 4 only 60. A tunnel diode is a p-n junction in which (a) n-region is degenerately doped (b) p-region is degenerately doped (c) either n or p-region is degenerately doped (d) both n and p-regions are degene-rately doped.

1.6

Basic Electronics Engineering

61. Which is the diode used for measuring light intensity? (a) Junction diode (b) Varactor diode (c) Tunnel diode

(d) Photo diode

62.

+10V

(a) Hall effect (b) Early effect

3k 100k

67. In a bipolar junction transistor an increase in magnitude of collector voltage increases the space-charge width at the ouput junction diode. This causes the effective base width to decreases. This effect is known as

(c) Miller effect  = 100

(d) Zener effect 68. Which type of protection is provided for SCR by connecting the snubber circuit across it?

+ _

The trans-conductance gm of the transis-tor used in the CE amplifier shown in the above circuit, operating at room temperature is (a) 92 mA/V

(b) 46 mA/V

(c) 184 mA/V

(d) 25 mA/V

63. Which of the following are essentials of a transistor biasing circuit? 1. Proper zero signal collector current flow 2. VCE should not fall below 0.5 V for Germanium and 1 V for Silicon 3. Ensure stabilization of operating point 4. Loading to the source (a) 1, 2, and 3 only (b) 1, 2, and 4 only (c) 3 and 4 only

dv protection dt di (b) protection dt (c) Over-voltage protection

(a)

VBB = 3V

(d) 1, 2, 3 and 4

64. When a transistor is saturated, (a) the emitter potential is more than the basecollector potential (b) the collector potential is more than the baseemitter potential (c) the base potential is more than the emittercollector potential (d) the base, emitter and collector are almost the same potential 65. If the value of a transistor changes 0.5% from its nominal value of 0.9, the percentage change in b will be (a) 0%

(b) 2.5%

(c) 5%

(d) 7.5%

66. If an npn silicon transistor is operated at VCE = 5 V and IC = 100 A and has a current gain of 100 in the CE connection, then the input resistance of this circuit will be (a) 250 

(b) 25 k

(c) 250 k

(d) 2500 k

(d) Over-current protection 69. Most of the linear ICs are based on two-transistor differential amplifiers because of (a) input voltage-dependent linear transfer characteristic (b) high voltage gain (c) high input resistance (d) high CMRR 70. When the photo resist coating (during IC fabrication) is exposed to ultraviolet light the photo resist becomes (a) oxidized

(b) ionized

(c) polymerized

(d) brittle

2012 71. The concentration of hole-electron pairs in pure silicon at T = 300 K is 7  1015 per cubic metre. Antimony is doped into silicon in a proportion of 1 atom in 107 atoms. Assuming that half of the impurity atoms contribute electrons in the conduction band, the factor by which the number of charge carriers increases due to doping (the number of silicon atoms per cubic metre is 5 028) is (a) 14  1015

(b) 0.5  1021

(c) 2.5  1021

(d) 1.8  105

72. A potential barrier of 0.50 V exists across a p-n junction. If the depletion region is 5.0  10–7 m wide, what is the intensity of the electric field in this region ? (a) 1.0  106 V/m

(b) 2.5  10–7 V/m

(c) 2.5  107 V/m

(d) 2.5  108 V/m

Basic Electronics Engineering

73. In a transconductance, the device output

89. Diodes are used to compensate which of the following transistor circuit parameters ?

(a) voltage depends upon the input voltage (b) voltage depends upon the input current

1. ICO

(c) current depends upon the input voltage

2. VBE

(d) current depends upon the input current

3. 

74. If the drift velocity of holes under a field gradient of 200 V/m is 100 m/s, their mobility in SI units is (a) 0.5

(b) 0.05

(c) 50

(d) 500

(b) 2 and 3 only

(c) 1 and 3 only

(d) 1, 2 and 3

(a) current-controlled negative resistance (b) voltage-controlled negative resistance

N(E) : Density of states

(c) temperature-controlled positive resistance

f (E) : Probability that a quantum state with energy E is occupied by an electron : Energy level of conduction band

The expression

(a) 1 and 2 only

80. The I-V characteristics of a tunnel diode exhibit?

75. Given

EC

1.7



EC N(E) f (E)dE

gives

(d) current-controlled positive resistance 81. A gate to drain-connected enhancement mode MOSFET is an example of (a) an active load

(a) minimum number of electrons in conduction band

(b) a switching device

(b) concentration of electrons in conduction band

(d) a diode

(c) energy of electron concentration in conduction band (d) conductivity of electrons in conduction band 76. Hall effect is useful for the measurement of a semiconductor’s (a) mobility, carrier temperature

concentration

and

(b) type (n-type or p-type), conductivity and temperature (c) type (n-type or p-type), mobility and carrier concentration (d) mobility, conductivity and temperature 77. A freewheeling diode in a phase-controlled rectifier (a) improves the line power factor (b) is responsible for additional reactive power (c) prevents inverse operation (d) is responsible for additional harmonics 78. The relative values of the forward conduction voltage for a p-n junction diode, a Red LED and a Schottky barrier diode are (a) Schottky voltage drop > p-n junction diode drop > Red LED drop (b) Red LED drop > p-n junction diode drop > Schottky voltage drop

(c) a three-terminal device 82. Thermal runaway is not possible in FET because, as the temperature of FET increases (a) the drain current increases (b) the mobility increases (c) the mobility decreases (d) the transconductance increases 83. The output impedance of a BJT under commoncollector configuration is (a) low

(b) high

(c) medium

(d) very high

84. Consider the following statements related to JFET : 1. Its operation depends on the flow of minority carriers only. 2. It is less noisy than BJT. 3. It has poor thermal stability. 4. It is relatively immune to radiation. The correct statements are (a) 1, 2, 3 and 4

(b) 1 and 2 only

(c) 2 and 4 only

(d) 3 and 4 only

85. For common-collector amplifier, the current gain (AI) is

(c) p-n junction diode drop > Schottky voltage drop > Red LED drop

(a) 1 + hfe

(d) Schottky voltage drop > Red LED drop > p-n junction diode drop

(c)

1  hfe hoe hie

(b)

(d)

1  hfe 1  hoe R L

1  hfe 1  hie R L