QP-ESEM-24-ELECTRONICS-TELECOMMUNICATION-ENGINEERING-PAPER-I-240624

Engineering Services (Mai Examination, ogo eee ELECTRONICS AND TELECOMMUNICATION ENGINEERING Paper - I Time Allowed : Three Hours Maximum Marks : 300 Question Paper Specific Instructions Please read each of the following instructions carefully before attempting questions : There are EIGHT questions divided in TWO sections. Candidate has to attempt FIVE questions in all. Questions No. 1 and 5 are compulsory and out of the remaining, any THREE are to be attempted choosing at least ONE question from each section. The number of marks carried by a question/part is indicated against it. Wherever any assumptions are made for answering a question, they must be clearly indicated. Diagrams/figures, wherever required, shall be drawn in the space provided for answering the question itself. Unless otherwise mentioned, symbols and notations have their usual standard meanings. Attempts of questions shall be counted in sequential order. Unless struck off, attempt of a question shall be counted even if attempted partly. Any page or portion of the page left blank in the Question-cum-Answer (QCA) Booklet must be clearly struck off. Answers must be written in ENGLISH only. Values of constants which may be required : Electron charge = — 1:6 x 10-19 Coulomb Free space permeability “= 47 x 10-7 Henry/m Free space permittivity = (1/367) x 10-9 Farad/m Velocity of light in free space = 3 x 108 m/s Boltzmann constant = 1:38 x 10°73 J/K Planck’s constant = 6-626 x 10-74J-s SGSE-O-ETE z 1. (2) (1) (c) () SECTION A Consider an ideal pMOS capacitor of area 100 um x 100 |) operated at T = 300 K. (work ‘function for the metal) = 5:2 eV, 2) (oxide thickness) = 3 nm and Np = 10!7/em®. Calculate the flat band voltage Vpg and the threshold voltage സന്തു. Assume = 3-43 x 1073 F/em, Vy (thermal voltage) = 0026 V, n; = 10!%cm3, 79; (electron affinity of Si) = 4-05 eV, Eg = 1.12 eV and Eg; = 10-2 F/em. 72 In the circuit shown in the figure below, 11] serves as an electronic switch. If . is very small, determine W/L such that circuit attenuates the signal by 5%. Assume Vg = 1:8 V and Ry, = 100 . pA Co, = 200 ye and ‎ = 0-4 V. 12 "5 © Vout in -M, Ry Find the voltage in the circuit shown in the figure using source transformation. Also, find the power developed by the 250 V voltage source. 250 50 AW 50 రెడీ =+ 15೧ 2 250 An electrical load absorbs an average power of 85 kW at lagging power factor of 0-85. If the load operates at 240 V rms, calculate the complex power and impedance of the load. 2 SGSE-O-ETE 2 fe) @ (ii) Draw neat sketches of the edge and screw dislocations. Illustrate the Burger’s vector on the sketches of dislocations. Calculate the line energy of dislocation in BCC iron if the shear modulus and lattice parameter of BCC iron are 80:2 GN/m? and 2-87 A, respectively. Q2. (a) Ap-njunction solar cell is fabricated using silicon and has the following important parameters : Na = 3x 1018 /em3, Np = 2 x 1016/em3 D, = 25 cm’/s, D, = 10 em?/s to =4X10-'s, T)O0 = 10-7 s The photocurrent density Jj, = 20 mA/cm?, Calculate the open circuit voltage of the solar cell at T = 300 K. Assume n;, = 1:5 x 101%cem3, (b) @ (ii) c)- - @) Gi) Q3. (a) (i) (ii) SGSE-O-ETE What are the two functions of commutator in DC machines ? Explain how the commutator keeps the armature mmf stationary in space, along the interpolar axis, even though the armature rotates. Explain why end-centred tetragonal geometry does not exist in Bravais crystal structures. Differentiate between different types of magnetic materials on the basis of magnetic dipoles and hysteresis loops. Design a Widlar current source shown in the figure below to give I, = 5 pA and Ip = 1 mA. The parameters are Vcc = 30 V, Vpri = 0:7 V, Vr = 26 mV and By = 100. Voc 777 Design an amplifier that has a voltage gain of 2 if Vqy < 0 and 1, if Vpy > 0. Assume ideal diodes and ideal op amps are available. = 6 6 20 5 15 10 10 10 10 (b) (c) (a) @ Gi) @ (a) Discuss the points of similarities between a transformer and induction machine. Explain, why an induction machine is called a generalized transformer. A 10 kVA/2500/250 V, single-phase transformer has the following parameters : Primary winding (h.v. side) : Resistance rj = 2-4 Q Leakage Reactance, x, = 6:00 Q Secondary winding (1.v. side) : Resistance ro = 0-03 Q Leakage Reactance, x9 = 0-07 Q With primary supply voltage held constant at 2500 V, calculate the secondary terminal voltage, when the low voltage winding is connected to a load impedance of 5 + j 3-5 Q and the transformer delivers its rated current at 0-8 p.f. lagging on the low voltage side. Discuss photoelectric effect and find out the number of photoelectrons emitted per unit time from a transmitter operated at a frequency of 800 kHz and 10 kW power. Define dielectric strength. Discuss different types of dielectric breakdowns in solids. For the circuit shown in the figure below, determine the frequency of oscillation f, and overall voltage gain A,. Also identify the type of oscillator. (Assume op amps are ideal) 1pF int i 1kQ DN e is 1kO 1p Ay WW If ae fe] Vol je [Von T7777 ANW. 4 10 10 10 10 20 ©) Determine the impedance Zy, that results in maximum average power transferred to , for the circuit shown in the figure. Calculate the maximum average power transferred to the load impedance determined. 10 50 130 ಕ್ಕೆ 000 9 20207 20 5 Q 360 . b (1) | What are the major factors that have led to the acceleration and development of solar and wind power ? 10 (c) To produce a p-type semiconductor, the boron is doped in pure silicon. Doping is done through a 3203 vapour phase of a surface concentration equivalent to 3-3 x 1026 boron atoms/m®. Calculate the time required to get a boron content of 1023 atoms/m? at a depth of 2 ym. The doping temperature is 1000°C and Dg inSi at this temperature is 4 x 10-177 m/s. 20 Given : erf (0-95) = 08209 erf (1-0) 7 erf (2-4) = 0-9993 erf (2-6) = 09998 SGSE-O-ETE SECTION B Q5. (a) Assume an ideal 10 bit ADC with Ver = 5 V is used to sample 1Vp_p sinusoidal signal that has a 2-5 V offset. What percent of error can be expected in the peak voltage measurement due to quantization effect of the ADC ? (The error is relative to the magnitude of the sinusoid). 12 555 IC is connected as shown in the figure below. Determine the frequency of oscillation and the duty cycle. (Assume that diode is an ideal diode). 12 Ra 10 kQ 8 7 | 1010 3] 2 6 == 1 5 C = 0.01 pF eile 0-01 pF] () The network of the figure contains both a dependent voltage source and a dependent current source. Determine the y and z parameters. 6 10 2] +0 < >> + , 310 0.1 2540 (ii) In the figure shown, a network with a steady state is reached with switch K open. At t = 0, the switch is closed. For the element values given, determine the value of v, (0—) and vg (0+). 102 WAM 102 Va 202 AAA T AW P%b K a ees: ARF 10Q (dad) @ For the figure shown, find i}. 22 WA 12 b AN MA >i, 19 he He lamp $10 @ev (ii) | The network of inductors in the figure below is composed of a 1 H inductor on each edge of a cube with the inductors connected to the vertices of the cube as shown. Find out the Lequivalent between the terminals A — B. (e) (a) (b) It is desired to measure the voltage across the 50 kQ resistor in the circuit shown in the figure. Two voltmeters are available for this measurement : Voltmeter 1 with sensitivity of 1000 Q/V and Voltmeter 2 with a sensitivity of 20,000 Q/V. Both meters are used on their 50 — V range. Calculate the reading of each meter. 12 WW 100 kQ O+ 150 V 50 kQ = For the circuit shown in the figure below, MOS and BJT are operating in saturation and active mode, respectively. The capacitor C is very large and Vy is small. The parameters of the transistors are ln Cox = 100 pA/V?, Voy = 1 V, L = 2 pm, Vp = 25 mV, Bp = 100, Vpr = 0:7 V and quiescent output voltage is 5 V. Size the MOSFET and calculate the small signal voltage gain A, = - 2 20 s ° Vout — ee v, = Viy sin (at + Q) 7777 Q cos o cos.cos( — B) reading for electrodynamometer type of watt meters, where, @) Prove that the true power = x actual watt meter cos $ = power factor of the circuit, 8 = tan~! oL/R where, L and R are the inductance and resistance of the pressure coil of the circuit. 10 Gi) Explain why errors are large when the power factor is low. 10 SGSE-O-ETE Fg ( : 0) Find the Thevenin’s equivalent for the circuit at terminalsa—b. 70 - 13000 1 200 (2 1100 1 ba 10020", (+ ) (+) 100490, ? (ii) For the ladder network determine the g parameters in the s domain. 10 LH 1H ‎ "1 “0- 12 1 Q7. (a) The parameters of the amplifier shown in the figure below are Ro, = 4 kQ, Rp = 2 ,‎ 709 = 5 kQ, Rp = 4 and Rg = 200 . The DC bias currents of the transistor are 101 = 0.5 mA, Ic, = 1 mA. The transistor parameters are hg, = hg, = hfe = 150. Use the techniques of feedback analysis to calculate the input resistance Ryp, the output resistance Roy and the closed loop transresistance gain Ar. Assume Vp = 25 mV. 20 4kQ AW Rp 200 ‎ 0 Rg + + Vo Vs 92 ‎ Ro, = ReZ2kQ > = @ Explain at least five advantages and disadvantages of LVDT. State at least two uses of LVDTs. 10 Gi) The output of an LVDT is connected to a 5 V voltmeter through an amplifier whose amplification factor is 200. An output of 2 mV appears across the terminals of LVDT when the core moves through a distance of 0-5 mm. Calculate the sensitivity of the LVDT and that of the whole set-up. The milli voltmeter scale has 100 divisions. The scale can be read to 1/5 of a division. Calculate the resolution of the instrument in mm. 10 (6) 2G) In the series RL circuit, the switch is in position 1 long enough to establish the steady state and is switched to position 2 at t = 0. Find the current i. 10 1 : 2 any 200 i ete 04H (i) Obtain the overall ABCD parameters of the circuit. 10 Z ne i ° 1 I oO [Js Qs. (a) (b) (i) Determine the functional behaviour of the circuit. Assume that input w is driven by a square wave signal. 10 J Q J Qr-Q, w > > K Q ik Q f > Clear (ii) In the circuit shown in the figure below, the gate voltage Vg is very small. Assume op amp is an ideal op amp, Vy = 1 V and Hy Coy W _ 200 pA ; 1 oltage. 1 L v2 Calculate output voltage 0 AWW 20 kQ av Gi) Describe the construction and working of a shunt type ohmmeter. Write down its design equations. 10 (ii) |The ohmmeter shown in the figure uses a 100 Q basic movement . requiring a full-scale current of 1 mA. The internal battery voltage is 3 V. The desired scale marking for half-scale deflection is 2000 Q. Calculate the value of R, and Rg, and the maximum value of Ry to compensate for a 10% drop in the battery voltage. 10 Ry A AWW 4 Oo < Ro Ru (A) = R, w (c) A series resonant network consists of a 50 Q resistor, a 4 mH inductor and a 0-1 uF capacitor. Calculate values for (a) os (b) fo, (c) Qo, (d) BW, (e) 4, (f) ag, (g) Zin at 45 k rad/sec, and (h), the ratio of magnitude of the capacitor impedance to resistor impedance at 45 k rad/sec. 20