Q.1 to Q.30 carry one mark each

Transcription

1 1 Q.1 to Q. carry one mark each Q.1 Conider the network graph hown in figure below. Which one of the following i NOT a tree of thi graph? Q. The equivalent inductance meaured between the terminal 1 and for the circuit hown in figure below i L 1 L M L 1 L M L1 L M L1 L M Q. The circuit hown in figure below with R 1/, L 1/ H, C = F ha input voltage ( t) in t. The reulting current i (t) i 5in(t 5.1 ) 5in(t 5.1 ) 5in(t 5.1 ) 5in(t 5.1 ) Q. For the circuit hown in figure below, the time contant RC = 1 n. The input voltage i ( t) in1. The output voltage ( ) i equal to t i t in(1 t 5 ) in(1 t 5 ) in(1 t 5 ) in(1 t 5 )

2 Q.5 For the R-L circuit hown in figure below, the input voltage ( t) u( t). The current i (t) i i Q. The impurity commonly ued for realizing the bae region of a ilicon n-p-n tranitor i Gallium Indium Boron Phophoru Q.7 If for a ilicon n-p-n tranitor, the bae-to-emitter voltage ( V EE ) i.7v and the collector-to-bae voltage ( V CE ) i.v, then the tranitor i operating in the normal active aturation mode invere active mode cutoff mode Q.8 Conider the following tatement S1 and S. S1 : The of a bipolar tranitor reduce if the bae width i increaed. S: The of a bipolar tranitor increae if the doping concentration in the bae i increaed. Which one of the following i correct? S1 i FALSE and S are TRUE Both S1 and S are FALSE Q.9 An ideal op-amp i an ideal Voltage controlled current ource Current controlled current ource Q.1 Voltage erie feedback (alo called erie-hunt feedback) reult in increae in both input and output impedance decreae in both input and output impedance increae in input impedance and decreae in output impedance decreae in input impedance and increae in output impedance Both S1 and S are TRUE S1 i TRUE and S i FALSE Voltage controlled voltage ource Current controlled voltage ource

3 Q.11 The circuit in figure below i a Low-pa filter High-pa filter Band-pa filter Band-reject filter Q.1 Auming V CEat. V and 5, the minimum bae current I ) required to drive the tranitor in figure below to aturation i ( B 5 A 1mA A ma Q.1 A mater-lave flip-flop ha the characteritic that Change in the input i immediately reflected in the output Change in the output occur when the tate of the mater i affected Change in the output occur when the tate of the lave i affected. Both the mater and the lave tate are affected at the ame time Q.1 The range of igned decimal number that can be repreented by -bit 1' complement number i -1 to +1 - to + - to + - to +1 Q.15 A digital ytem i required to amplify a binary-encoded audio ignal. The uer hould be able to control the gain of the amplifier from a minimum to a maximum in 1 increment. The minimum number of bit to encode, in traight binary, i Q.1 Chooe the correct one from among the alternative A, B, C, D after matching an item from Group 1 with the mot appropriate item in Group. Group 1 Group P: Shift regiter 1: Frequency diviion Q: Counter : Addreing in memory chip R: Decoder : Serial to parallel data converion P P P P 1 Q Q 1 Q 1 Q R 1 R R R

4 Q.17 Figure how the internal chematic of TTL AND-Or-Invert (AOI) gate. For the input hown in fig. Q.17, the output Y i 1 AB AB Q.18 Figure i the voltage tranfer characteritic of an NMOS inverter with enhancement mode tranitor a load An NMOS inverter with depletion mode tranitor a load A CMOS inverter A BJT inverter Q.19 The impule repone h(n) of a linear time-invariant ytem i given by h [ n] u[ n ] u[ n ] u[ n 7] When u [n] i the unit tep equence. The above ytem i Stable but not caual Caual but untable Stable and caual untable and not caual Q. The ditribution function F x (x) of a random variable X i hown in figure below. The probability that X = 1 i Zero Q.1 The z-tranform of a ytem i z H ( z) z. If the ROC i z., then the impule repone of the ytem i n (.) u[ n] (.) u[ n 1] n n (.) u[ n] (.) u[ n 1] n

5 5 Q. The Fourier tranform of a conjugate ymmetric function i alway. imaginary Real Q. The gain margin for the ytem with open-loop tranfer function Q. Given (1 ) G( ) H ( ), i conjugate anti-ymmetric Conjugate ymmetric 1 K G ( ) H ( ) ( 1)( ) The point of interection of the aymptote of the root loci with the real axi i Q.5 In a PCM ytem, if the code word length i increaed from to 8 bit, the ignal to quantization noie ratio improve by the factor 8/ Q. An AM ignal i detected uing an envelope detector. The carrier frequency and modulating ignal frequency are 1 MHz and MHz repectively. An appropriate value for the time contant of the envelope detector i 5 ec ec. ec 1 ec Q.7 An AM ignal and a narrow-band FM ignal with identical carrier, modulating ignal and modulation indice of.1 are added together. The reultant ignal can be cloely approximated by Broadband FM SSB with carrier DSB-SC SSB without carrier Q.8 In the output of a DM peech encoder, the conecutive pule are of oppoite polarity during time interval t1 t t. Thi indicate that during thi interval the input to the modulator i eentially contant the modulator i going through lope overload the accumulator i in aturation the peech ignal i being ampled at the Nyquit rate Q.9 The phae velocity of an electromagnetic wave propagating in a hollow metallic rectangular waveguide in the TE 1 mode i equal to it group velocity le than the velocity of light in free pace equal to the velocity of light in free pace Greater than the velocity of light in free pace

6 Q. Conider a lole antenna with a directive gain of + db. If 1mW of power i fed to it the total power radiated by the antenna will be mw 1 mw 7 mw 1/ mw Q.1 to Q.9 carry two mark each Q.1 For the lattice circuit hown in figure below, Z and Z. The value of the open circuit impedance parameter j Z 11 Z Z 1 are Z 1 Z b 1 j 1 j 1 j 1 j 1 j 1 j 1 j 1 j 1 j 1 j 1 j 1 j 1 j 1 j 1 j 1 j Q. The circuit hown in figure below ha initial current i L ( ) 1A through the inductor and an initial voltage C ( ) 1V acro the capacitor. For input ( t) u( t), the Laplace tranform of the current i (t) for t i 1 1 Q. Conider the Bode magnitude plot hown in figure. The tranfer function H() i ( 1) ( 1) ( 1) 1( 1) ( 1) ( 1) ( 1) ( 1 1) ( 1) 1 ( 1) ( 1) ( 1) Q. The tranfer function V ( ) H ( ) of an R-L-C circuit i given by V ( ) i H ( ) 1 1

7 7 The Quality factor (Q-factor) of thi circuit i Q.5 For the circuit hown in figure below, the initial condition are zero. It tranfer function H( ) V ( ) / V ( ) i C i Q. A ytem decribed by the following differential equation d y dy y x( t) dt dt i initially at ret. For input x( t) u( t), the output y(t) i t t t (1 e e ) u( t) (1 e e ) u( t) t t (.5 e 1.5e ) u( t) (.5 e e ) u( t) Q.7 Conider the following tatement S1 and S. t t S1 : At the reonant frequency the impedance of a erie R-L-C circuit i zero. t S: In a parallel G-L-C circuit, increaing the conductance G reult in increae in it Q factor. Which one of the following i correct? S1 i FALSE and S i TRUE S1 i TRUE and S i FALSE Both S1 and S are TRUE Both S1 and S are FALSE Q.8 In an abrupt p-n junction, the doping concentration on the p-ide and n-ide are N A 91 1 / cm repectively. The p-n junction i revere biaed and the total depletion width i m. The depletion width on the p-ide i.7m.m.5m.75m Q.9 The reitivity of a uniformly doped n-type ilicon ampled i.5 cm. If the electron mobility ) i 15 cm / V ec and the charge of an electron i ample i 1 1 / cm / cm 1. 1 coulomb, the donor impurity concentration N ) in the / cm / cm Q. Conider an abrupt p-n junction. Let V bi be the built-in potential of thi junction and V be the applied revere bia. If the junction capacitance ( C ) i 1 pf for V V 1V, then for V V, C will be j bi R V bi R j pf pf.5 pf.5 pf ( n ( D

8 8 Q.1 Conider the following tatement S1 and S. S1: the threhold voltage ( V T ) of a MOS capacitor decreae with increae in gate oxide thickne. S: the threhold voltage ( V T ) of a MOS capacitor decreae with increae in ubtrate doping concentration. Which one of the following i correct? S1 i FALSE and S i TRUE Both S1 and S are FALSE Both S1 and S are TRUE S1 i TRUE and S i FALSE Q. The drain of an n-channel MOSFET i horted to the gate o that VGS VDS. The threhold voltage ( V T ) of the MOSFET i 1 V. If the drain current ( I D ) i 1mA for V GS V, then for V GS V, I D i ma ma 9 ma m Q. The longet wavelength that can be aborbed by ilicon, which ha the bandgap of 1.1 ev, i 1.1 m. If the longet wavelength that can be aborted by another material i.87 m, then the bandgap of thi material i 1.1 ev.88 ev.85 ev.7 ev Q. The neutral bae width of a bipolar tranitor, biaed in the active region, i.5 m. The maximum electron concentration and the diffuion contant in the bae are 1 cm and D n 5cm / ec repectively. Auming negligible recombination in the bae, the collector current denity i (the electron charge i Coulomb) 8 A / cm 9 A / cm 1 / A / cm Q.5 Aume that the of the tranitor i extremely large and V BE.7V, I C and below are A / cm V CE in the circuit hown in figure I 1mA, V.7 V I.5mA, V.75V C CE I 1mA, V.5V I.5mA, V.9 V C CE Q. A bipolar tranitor i operating in the active region with a collector current of 1 ma. Auming that the of the tranitor i 1 and the thermal voltage ( V T ) i 5mV, the Tranconductance ( g m ) and the input reitance ( r ) of the tranitor in the common emitter configuration, are g m 5mA/ V and r 15. 5k g m ma/ V and r. k g m 5mA/ V and r. 5k g m ma/ V and r. 5k C C CE CE

9 9 Q.7 The value of C required for inuoidal ocillation of frequency 1 KHz in the circuit of figure below i 1 F 1 F F Q.8 In the op-amp circuit given in figure below, the load current i L i F R R R Q.9 In the voltage regulator hown in figure below, the load current can vary from 1 ma to 5 ma. Auming that a Zener diode i ideal (i.e. the Zener knee current i negligibly mall and Zener reitance i zero in the breakdown region), the value of R i L R / 1 Q.5 In a full-wave rectifier uing two ideal diode, V dc and V m are the dc and peak value of the voltage repectively acro a reitive load. If PIV i the peak invere voltage of the diode, then the appropriate relationhip for thi rectifier are Vm Vm Vdc, PIV V m I dc, PIV Vm V dc V, m m PIV V m Vdc, PIV Vm V

10 1 Q.51 The minimum number of -to-1 multiplexer required to realize a -to-1 multiplexer i 1 Q.5 The Boolean expreion AC BC i equivalent to AC BC AC BC AC BC ACB AC BC BC ABC ABC ABC ABC ABC Q.5 111, 11 and 1111 correpond to the ' complement repreentation of which one of the following et of number? 5, 9 and 57 repectively -7, -7 and -7 repectively -, - and - repectively -5, -9 and -57 repectively Q.5 The 855 programmable peripheral Interface i ued a decribed below. (i) An A/D converter i interfaced to a microproceor through an 855. The converion i initiated by a ignal from the 855 on Port C. A ignal on Port C caue data to be tobed into Port A. (ii) Two computer exchange data uing a pair of 855. Port A work a a bidirectional data port upported by appropriate handhaking ignal. The appropriate mode of operation of the 855 for (i) and (ii) would be Mode for (i) and Mode 1 for (ii) Mode for (i) and Mode for (ii) Mode 1 for (i) and Mode for (ii) Mode for (i) and Mode 1 for (ii) Q.55 The number of memory cycle required to execute the following 885 intruction (i) LDA H Would be for (i) and for (ii) for (i) and for (ii) (ii) LXI D, FOF1H for (i) and for (ii) for (i) and for (ii) Q.5 In the modulo- ripple counter hown in figure below, the output of the -input gate i ued to clear the J-K flipflop. The -input gate i A NAND gate A NOR gate an OR gate an AND gate

11 11 Q.57 Conider the equence of 885 intruction given below LXI H, 958 MOV A, M CMA MOV M, A Which one of the following i performed by thi equence? Content of location 958 are moved to the accumulator Content of location 958 are compared with the content of the accumulator Content of location 859 are complemented and tored in location 859 Content of location 589 are complemented and tored in location 589 Q.58 A Boolean function f of two variable x and y i defined a follow : f (, ) f (, 1) f (1, 1) 1; f (1, ) Auming complement of x and y are not available, a minimum cot olution for realizing f uing only -input NOR gate and -input OR gate (each having unit cot) would have a total cot of 1 unit unit unit unit Q.59 It i deired to multiply the number AH by BH and tore the reult in the accumulator. The number are available in regiter B and C repectively. A part of the 885 program for thi purpoe i given below : LOOP : MVI A, H HLT END The equence of intruction to complete the program would be JNZ LOOP, ADD B, DCR C DCR C, JNZ LOOP, ADD B ADD B, JNZ LOOP, DCR C ADD B, DCR C, JNZ LOOP Q. A 1 KHz inuoidal ignal i ideally ampled at 15 ample/ec and the ampled ignal i paed through an ideal low-pa filter with cut-off frequency 8 Hz. The output ignal ha the frequency zero Hz.75 KHz.5 KHz.5 KHz Q.1 A rectangular pule train (t) a hown in figure below i convolved with the ignal co ( 1 t). The convolved ignal will be a DC 1 KHz Sinuoid 8 KHz inuoid 1 KHz inuoid

12 1 Q. Conider the equence x[ n] [ j5 1 j 5] The conjugate anti-ymmetric part of the equence i [- j5 j j5] [-j5 1 j.5] [-j.5 j ] -, 1 ] Q. A caual LTI ytem i decribed by the difference equation y[ n] y[ n] x[ n] x[ n1] The ytem i table only if,,, any value of, any value of Q. A caual ytem having the tranfer function 1 H ( ) i excited with 1u ( t). The time at which the output reache 99% of it teady tate value i.7 ec.5 ec. ec.1 ec Q.5 The impule repone h [n] of a linear time invariant ytem i given a n 1, 1 h [ n] n, otherwie j n / e If the input to the above ytem i the equence, then the output i j n / e e j n / j n/ e j n/ e Q. Let x (t) and y (t) with Fourier tranform F(f) and Y(f) repectively be related a hown in figure below. Then Y ( f ) i 1 jf X ( f / ) e 1 jf X ( f / ) e jf X ( f / ) e X ( f / ) e Q.7 A ytem ha pole at.1 Hz, 1 Hz and 8 Hz; zero at 5 Hz, 1 Hz and Hz. The approximate phae of the ytem repone at Hz i jf

13 1 Q.8 Conider the ignal flow graph hown in figure below. The gain Q.9 If A 1 1 (be cf dg) abcd abcd 1 ( be cf dg) bedg, then in At i in( t) in( t) in( t) in( t) in( t) in( t) in( t) in( t) x x 5 1 i bedg 1 ( be cf dg) 1 ( be cf dg) bedg abcd in( t) in( t) in(t ) in( t) in(t) in( t) in( t) in( t) co( t) co( t) in( t) in t in(t) in( t) co( t) in( t) Q.7 The open-loop tranfer function of a unity feedback ytem i K G ( ) ( ) ( ) The range of K for which the ytem i table i 1 1 K 1 K K Q.71 For the polynomial P ( ) 15 5 The number of root which lie in the right half of the -plane i 1 Q.7 The tate variable equation of a ytem are : x x x u, x x y x u Controllable but not obervable Neither controllable nor obervable Q.7 Given A 1, the tate tranition matrix , 1 At e i given by co( t) in( t) co(t ) co( t) K Obervable but not controllable Controllable and obervable t e t e t e t e t e t e t e t e Q.7 Conider the ignal x(t) hown in figure below. Let h(t) denote the impule repone of the filter matched to x (t), with h (t) being non-zero only in the interval to ec. The lope of h (t) in the inverval t ec i 1 1 ec 1 1ec 1 1/ ec 1ec 1

14 1 Q.75 A 1 mw video ignal having a bandwidth of 1 MHz i tranmitted to a receiver through a cable that ha db lo. IF the effective one-ided noie pectral denity at the receiver i 1 Watt/Hz, then the ignal-to-noie ratio at the receiver i 5 db db db db Q.7 A 1 MHz carrier of 1V amplitude and a 1 MHz modulating ignal of 1 V amplitude are fed to a balanced modulator. The output of the modulator i paed through an ideal high-pa filter with cut-off frequency of 1 MHz. The output of the filter i added with 1 MHz ignal of 1V amplitude and 9 phae hift a hown in figure below. The envelope of the reultant ignal i t Contant 1 in( 1 ) 5/ in( 1 ) 5/ co( 1 ) Q.77 Two inuoidal ignal of ame amplitude and frequencie 1 KHz and 1.1 KHz are added together. The combined ignal i given to an ideal frequency detector. The output of the detector i.1 KHz inuoid a linear function of time.1 KHz inuoid a contant Q.78 Conider a binary digital communication ytem with equally likely ' and 1'. When binary i tranmitted the voltage at the detector input can lie between the level -.5V and +.5 V with equal probability; when binary 1 I tranmitted, the voltage at the detector can have any value between and 1 V with equal probability. If the detector ha a threhold of.v (i.e the received ignal i greater than.v, the bit i taken a 1), the average bit error probability i Q.79 A random variable X with uniform denity in the interval to 1 i quantized a follow: if X., x if. X 1, x. 7 q q Where x q i the quantized value of X. The root-mean quare value of the quantization noie i Q.8 Chooe the correct one form among the alternative A, B, C, D after matching an item from Group 1 with the mot appropriate item in Group. Group 1 Group 1: FM P: Slope overload : DM Q: law : PSK R : Envelope detector : PCM S: Capture effect T: Hilbert tranfer U: Matched filter t t

15 15 1-T 1-S 1 S 1 U P U P R U P U S S T Q Q Q.81 Three analog ignal, having bandwidth 1Hz, Hz and Hz are ampled at their repective Nyquit rate, encoded with 1 bit word, and time diviion multiplexed. The bit rate for the multiplexed ignal i 1, 15. kbp 8.8 kbp 7. kbp 8. kbp Q.8 Conider a ytem hown in figure below. Let X(f) and Y(f) denote the Fourier tranform of x (t) and y(t) repectively. The ideal HPF ha the cutoff frequency 1 KHz. The poitive frequencie where Y(f) ha pectral peak are 1 KHz and KHz 1 KHz and 1 KHz Q.8 A parallel plate are-filled capacitor ha plate area of 1 m KHz and KHz KHz and 1 KHz and plate eparation of 9 m V,. GHz ource. The magnitude of the diplacement current i ( 1/ 1 F / ) 1 ma 1 ma 1 A 1.59 ma 1 m. It i connected to a.5 Q.8 A ource produce binary data at the rate of 1 kbp. The binary ymbol are repreented a hown in figure below. The ource output i tranmitted uing two modulation cheme, namely Binary PSK (BPSK) and Quandrature PSK(QPSK). Let B 1 and B be the bandwidth requirement of BPSK repectively. Auming that the bandwidth of the above retangular pule i 1 KHz, B 1 and B are B1 KHz, B KHz B1 1 KHz, B 1KHz B1 KHz, B 1KHz B1 1 KHz, B 1KHz

16 1 Q.85 Conider a, quanter-wave long (at 1 GHz) tranmiion line a hown in figure below. It i connected to a 1V, 5 ource at one end and i left open circuited at the other end. The magnitude of the voltage at the open circuit end of the line i 1 V 5 V V /7 V Q.8 In a microwave tet bench, why i the microwave ignal amplitude modulated at 1 KHz? To increae the enitivity of meaurement to tudy amplitude modulation jkz jt Q.87 If E ( aˆ jaˆ ) e and H ( k / )(ˆ a jaˆ ) e x y y x jkz jt to tranmit the ignal to a far-off place Becaue crytal detector fail at microwave frequencie, the time-averaged pointing vector i Null vector ( k / ) â ( k / ) â ( k / ) z Q.88 Conider an impedance Z = R + jx marked with point P in an impedance Smith chart a hown in figure below. The movement from point P along a contant reitance circle in the clockwie direction by an angle 5 i equivalent to z â z adding an inductance i erie with Z adding an inductance in hunt acro Z adding a capacitance in erie with Z adding a capacitance in hunt acro Z Q.89 A plane electromagnetic wave propagating in free pace i incident normally on a large lab of lo-le, nonmagnetic,dielectric material with. Maxima and minima are oberved when the electric field i meaured in front of the lab. The maximum electric field i found to be 5 time the minimum field. The intrinic impedance of the medium hould be 1 Q.9 A lole tranmiion line i terminated in a load which reflect a part of the incident power. The meaured VSWR i. The percentage of the power that i reflected back i END OF THE QUESTION PAPER