PAPER II ELECTRONICS

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Ezra Hill
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1 PAPR II LCTRONICS Note : Answer all the questions. ach question carries two (2) marks. 1. For the given circuit C R L the second approximation is 1) R in series with L 2) L parallel with C 3) C parallel with R 4) R is series with C 2. The value of R in ohm in the given circuit is A 1 x O R B 10 V 2 C 1) 2 2) 4 3) 0 4) 6 3. The given circuit is C 1 D 1 1) Clipper 2) Clamper 3) Voltage doubler 4) Impedance matching C 2 4. If h F =250, dc = 250 for a transistor, then dc is 1) 250 2) 1 3) )

2 5. The data for a given transistor for a typical value of I C = 1 ma, are h ie = 3.5 k, h fe = 120, h re = 1.3(10 4 ) h oe = 8.5 s. The r ' is e 1) 992 2) ) 175 4) The source follower circuit has 1) low input resistance 2) extremely high input resistance 3) varying drain source voltage 4) forward bias on the gate-source terminal 7. The JFT circuit is given below with g mo = 3000 s I DSS = 3 ma Vout Vin 1 M 220 The dc voltage from drain to ground is 1) 17.6 V 2) 0.66 V 3) 12.4 V 4) 6.2 V 8. The bonding of atoms in rare earth gas are due to 1) metallic 2) coulombic 3) dipole-dipole interaction 4) covalent 9. In the JFT the pinch off voltage is the voltage 1) above which drain current is constant 2) above which drain voltage is constant 3) below which Gate current is constant 4) above which gate voltage is constant 10. The negative resistance which arises in tunnel diode refers 1) ac power is produced 2) ac power is absorbed 3) ac power is zero 4) dc power is absorbed 4

3 11. Select the wrong statement. In the node voltage technique of solving network, choice of a reference node does not 1) affect voltages of various nodes 2) affect the operation of the circuit 3) change the voltage across any element 4) affect the potential difference between any pair of nodes 12. In the given circuit, if the applied voltage across C-D is 100 V, the short circuit current flowing through the terminal A-B is A C + 10V B Linear Passive network D 1A 1) 0.1A 2) 1A 3) 10A 4) 100A 13. In the given circuit the current through 3 resistance is 3 2 V 2 4V 2 2 4V 1) 1.5 A 2) 0.66 A 3) 0 A 4) 8 3 A 14. If 1 = A sin t and 2 = B sin t then 1) 1 lags behind 2 by 2) 1 is in phase with 2 3) 2 leads 1 by 4) 2 lags by The reactance offered by a capacitor in an A.C circuit of frequency 50 Hz is 10. If the frequency is doubled, the reactance becomes 1) 20 2) 5 3) 2.5 4) The r.m.s value of half-wave rectified current is 10 A, its value for full wave rectifier is 1) A 2) 20 A 20 3) A 40 4) A 5

4 17. The maximum power transfer in the given circuit is A R + R RL 1) R 4 2 R 2 3) 4 R R 2) 4) B R R R R 18. The value of z in the given circuit to cause a parallel resonance at 500 Hz is 5 2H z 1) 125 mh 2) F 3) 2.0 F 4) 0.05 F 19. In the R.L circuit connected to an alternating sinusoidal voltage, size of transient current primarily depends on 1) the instant in the voltage cycle at which circuit is closed 2) peak value of the steady state current 3) the circuit impedance 4) the voltage frequency 20. The Fourier transform of a function ax y e is 1) Lorentian 2) Gaussian 3) Delta function 4) xponential With the combination of biased positive and negative clippers, one can get 1) sine wave 2) square wave 3) a saw tooth 4) a ramp v If s is the slow rate off op-amp, 10 V is the peak of output sine wave, then the highest undistorted frequency one would get is 1) 7.41 KHz 2) 7.96 KHz 3) 2.25 KHz 4) 22.5 KHz 6

5 23. If the open loop gain of an op-am p is 10 5, the output voltage is 10 V, input impedance is 2 M the input current is 1) 0.1 na 2) 0.1 ma 3) 0.05 ma 4) 0.05 na 24. The given circuit is a C V out R 1 R 2 + 1) active high pass filter 2) active low pass filter 3) active band pass filter 4) an active oscillator 25. The third odd harmonics for the given waveform is 50 s 1) 20 KHz 2) 40 KHz 3) 60 KHz 4) 100 KHz 26. The given circuit is 1) Darlington pair 2) Push-pull 3) UJT 4) SCR 7

6 27. Holding current in UJT is 1) maximum current that keeps latch open 2) minimum current that keeps latch closed 3) minimum current that keeps latch open 4) maximum current that keeps latch closed 28. The V out of the given circuit is Vout + =? 1) 2) 3) 4) 29. If the transistor is operated in the cutoff region of dc load line, all the supply voltage would appear across 1) Collector mitter 2) Base collector 3) Base emitter 4) Collector ground 30. If G 1, G 2, G 3 Gn are power gains of various stages of an amplifier the overall power gain of cascaded stages is G1 G3 G5 1) G 1 G2 G3... Gn 2)..... G G G G1 G2 G2 G3 G3 G4 3) G 1 G2 G3 4)..... G G G The unit of mobility of semiconductor is 1) m 2 v 1 s 1 2) m v 1 1 s 3) v sm 1 4) v ms Which of the following chip is used in 8085 microprocessor 3-chip configuration? 1) IC ) IC ) IC ) IC

7 33. C program is as follows: The result of the program is int i; /* declare integer i */ i=10; /* set i to 10 */ i=i+ A ; /* add character A */ /* to integer i */ print f ( i=%d, i); 1) 55 2) 51 3) 71 4) For a SMF, following characteristic are given by (a) 0 V (b) V (c) Core radius is less than 10 m (d) Attenuation is of the order of 1 db/km Which of the following statement is true? 1) (a) and (d) is correct 2) (b) and (c) is correct 3) (a) and (c) is correct 4) (c) and (d) is correct 35. A signal m f 5 sin 2 100t frequency modulates a carrier. The resulting FM signal 5 is 10 cos 2 10 t 15 sin t. The approximate bandwidth of FM signal is 1) 0.1 khz 2) 1 khz 3) 2 khz 4) 4 khz 36. In an SCR, dual converter circuit 1) 90 2) ) 270 4) Zener breakdown mechanism occurs in reverse biased PN junction 1) When P and N regions are lightly doped 2) When P and N regions are heavily doped 3) Are of silicon material only 4) When P and N regions are equally doped 38. In the venin equivalent circuit which is incorrect 1) Independent voltage sources are open circuited 2) Independent voltage sources are short circuited 3) Dependent voltage sources are removed 4) Current sources are opened 9

8 39. The transfer function of RC low-pass filter network 1) RCs/1 + RCs 2) 1/1 + RCs 3) RC/1 + RCs 4) S/1 + RCs 40. int Net = 0; if x < 50 if (y > 5) Net = x + y; else Net = x y; For this C program segment, x = 55 and y = 5, then the value Net is 1) 0 2) 60 3) 50 4) Which of the following digital modulation systems support high Bit rate? 1) ASK 2) PSK 3) FSK 4) ASK and FSK 42. In a normal CG wave form, which wave has the maximum amplitude? 1) P-wave 2) R-wave 3) Q-wave 4) T-wave 43. The condition for a two-port network to be reciprocal is 1) Z11 Z22 2) Y21 Y22 3) h21 h12 4) h21 h How many flip-flops are required to build a digital counter to count from 0 to 1024? 1) 11 2) 6 3) 10 4) Consider the following C program: #include<stdio.h> main ( ) { int i; int *pi = &i; scanf( %d,pi); printf( %d\n, i+5); } Which of the following statements is TRU? 1) compilation fails 2) execution results in run-time error 3) on execution, the value printed is 5 more than the address of variable i 4) on execution, the value printed is 5 more than the integer value entered 10

9 46. In Half Duplex (HDX), data transmission is possible 1) In one direction 2) In both direction 3) In both direction, but not at the same time 4) In both direction simultaneously 47. When the modulation index of an AM wave is doubled, the antenna current is also doubled. The AM system being used is 1) Single-sideband, full carrier (H3) 2) Vestigial sideband (C3F) 3) Single-sideband, suppressed carrier (J3) 4) Double-sideband, full carrier (A3) 48. An amplifier has open-loop voltage gain of 40.10% of negative feedback is effected. What will be the gain with feedback? 1) 40 2) 32 3) 16 4) If the various logic families are arranged in the ascending order of their fan-out capabilities, the sequence will be 1) TTL, DTL, CL, MOS 2) DTL, TTL, MOS, CL 3) MOS, DTL, TTL, CL 4) CL, TTL, DTL, MOS 50. In a 8085 microprocessor, the resistor which holds address of the next instruction to be fetched is 1) Accumulator 2) Program counter 3) Stack pointer 4) Instructor Register 51. Consider the following structure and declaration: struct date { int day; int month; int year; }; Struct data *pd ; Which of the following is the correct method to refer to the year member? 1) (*pd) year 2) (*pd) * year 3) (*pd) year 4) pd year 52. In a rectangular metallic waveguide (a) Guided wavelength is never less than the free space wavelength (b) TM mode is possible if the dimensions are properly chosen (c) v v 2 C (d) p g Waves travel along all the four walls of the waveguide 1) Options (a) and (c) are correct 2) Options (c) and (d) are correct 3) Options (b) and (c) are correct 4) Options (a) and (d) are correct 11

10 53. A certain D-MOSFT is biased at V GS 0v. Its data sheet specifies I DSS = 20 ma and V GS(off) = 5V. The value of the drain current is 1) 20 ma 2) 0 ma 3) 40 ma 4) 10 ma 54. Superposition theorem can be applied only to circuits having 1) Resistive elements 2) Passive elements 3) No-linear elements 4) Linear bilateral elements 55. In the mode word format of 8251 during initialization, D 6 and D 7 bits as 0 and 1 signify 1) 16 X Baud Rate 2) Character length as 7 bits 3) Parity enable and even parity 4) No. of stop bits as 1(1/2) 56. When the Q of an antenna increases, the bandwidth 1) increases 2) decreases 3) remains constant 4) equal to unity 57. Time-Division Multiplexing 1) can be used with PAM only 2) combines five groups into a super group 3) stacks 24 channels in adjacent frequency slots 4) interleaves pulses belonging to different transmissions 58. In CRO astigmatism is 1) Source of generating fast electrons 2) Media for absorbing secondary emission electrons 3) An additional focus control 4) Time-delay control in the vertical deflection system 59. The Laplace transform converts integral-differential equation in domain. 1) 6 2) S 3) jw 4) 60. An amplifier has an open loop gain of 100 and its lower and upper hand frequency of 100 Hz and 100 KHz, respectively. A feedback network with a feedback factor of 0.99 is connected to the amplifier; the new lower and uppercut off frequencies are at 1) f H = 10 MHz and f L = 1 Hz 2) f H = 25 MHz and f L = 10 Hz 3) f H = 100 MHz and f L = 100 Hz 4) f H = 10 MHz and f L = 10 Hz 12

11 61. K-map method of simplifications cannot be applied when the given functions is in (a) Sum of product forms (b) Product of sum forms (c) Canonical forms (d) Can be applied to all forms 1) (a) and (b) are correct 2) (a), (b) and (d) are correct 3) (c) only 4) (b) and (d) are correct 62. A signal varies from 20 Hz to 5 KHz is passed using pulse modulation scheme. Minimum sampling rate and number of channels that could be accommodated using TDM (assume each sample takes 10 s) respectively will be 1) 5 KHz, 5 2) 10 KHz, 5 3) 5 KHz, 10 4) 10 KHz, SCR turns off from conducting state to blocking state on 1) Reducing gate current 2) Reversing gate current 3) Reducing anode current below holding current value 4) Applying ac to the gate 64. Which equivalent circuits are dual? 1) Norton-Telleng 2) Thevenin-Superposition 3) Norton-Thevenin 4) Thevenin-Millman 65. Consider the following statement (a) A flip-flop is used to store 1-bit of information. (b) Race-around condition occurs in J-K flip-flop when both the inputs are 1. (c) Master-slave configuration is used in flip-flop to store 2-bits of information. (d) A transparent latch consists of D type flip-flop. Which of the following statements is/are true? 1) (a) only 2) (a), (c) and (d) 3) (a), (b) and (d) 4) (b) and (c) only p instructions are given below (a) (b) (c) (d) STA addr CALL addr MOV Rd, Rs ADI data Arrange these in the ascending order of number of clock cycles required to execute them. 1) (a), (b), (c), (d) 2) (c), (d), (a), (b) 3) (b), (d), (c), (a) 4) (d), (c), (b), (a) 13

12 67. Which of the following open statements are illegal? 1) fp = fopen( abc.txt, ( r ); 2) fp = fopen( /home/user/abc.txt, w ); 3) fp = fopen( abc. w ); 4) none of the above 68. What is the carrier frequency in an AM wave when its highest frequency component is 850 Hz and the bandwidth of the signal is 50 Hz? 1) 80 Hz 2) 695 Hz 3) 625 Hz 4) 825 Hz 69. The various components in super heterodyne receiver is arranged as (a) AM Detector (b) Mixer (c) RF Amplifier (d) AF Amplifier The correct sequence is 1) (c), (b), (a), (d) 2) (a), (b), (d), (c) 3) (c), (b), (d), (a) 4) (b), (a), (c), (d) 70. The Laplace transform of sin 2 3t is given by 1) 18 s s 36 2) 2 6 s /36 3) 18 (s 6) s s 36 4) 1 6 s s The ripple factor of a half-wave rectifier is found to be 1) ) ) ) The figure of merit of logic family is given by 1) Gain bandwidth product 2) (Propagation delay time) (power dissipation) 3) (Fan out) (propagation delay time) 4) (Noise margin) (power dissipation) 73. DS directive in ) forces the assembler to reserve one byte of memory 2) forces the assembler to reserve a specified number of bytes in the memory 3) forces the assembler to reserve a specified number of consecutive bytes in the memory 4) none of the above 14

13 74. In a FORTRAN program I have set x 2. 0 and b * ** What is the value of y if y a x b 2 / x? 1) 8.0 2) ) ) An air filled rectangular waveguide has dimensions 6 cm 4 cm. The cut off frequency for T 10 is 1) 2.5 GHz 2) 25 MHz 3) 20.5 GHz 4) 5 GHz 76. The phase method for generation of a SSB signal is most suitable for 1) data signals 2) weak modulating signals 3) larger bandwidth modulating signals 4) smaller bandwidth modulating signals 77. The step-index mono mode fiber has diameter 1) 10 m 2) 50 m 3) 100 m 4) 200 m 78. Tunnel diode is basically a junction diode with 1) High doping in P-region alone 2) High doping in p and n regions, both 3) High doping in n region alone 4) Low doping in both P and n regions 79. In 8085, example for Non-maskable interrupts is 1) Trap 2) RST 6.5 3) INTR 4) RSTO 80. Which of the following is not a valid property of a PARAMTR statement? 1) Can combine other parameters with FORTRAN arithmetic 2) Parameters can be set anywhere in a program 3) Integer parameters can be used to set array dimensions 4) Parameters can be used as bounds on do loops 81. Poynting Vector for an electromagnetic wave is 1) 3) H 2) H H 4) H 15

14 82. A 20 kw carrier is sinusoidally modulated by two carriers corresponding to modulation index of 30% and 40% respectively. The total radiated power is 1) 25 kw 2) 22.5 kw 3) 45.0 kw 4) 35.0 kw 83. The sinusoidal transfer functions are commonly represented by 1) Routh s criteria 2) Nyquist criteria 3) Bode Plot 4) Root Locas 84. A breakdown which is caused by cumulative multiplication of carriers through field induced impact ionization occurs in 1) Avalanche diode 2) Tunnel diode 3) Varactor diode 4) Gunn diode 85. Norton s current is equal to the current passing through the circuited terminals. 1) short, input 2) short, output 3) open, output 4) open, input 86. The input stage of an OP-amp is usually a 1) Differential amplifier 2) Class B push-pull amplifier 3) C amplifier 4) Swamped amplifier 87. In positive logic, logic state I corresponds 1) positive voltage 2) zero voltage 3) lower voltage level 4) higher voltage level 88. Which is not a proper way of array declaration? 1) int num [6] = {2, 4, 12, 5, 45, 5} 2) int a(25) 3) int n [ ] = {2, 4, 12, 5, 45, 5} 4) float press [ ] = {12.3, 34.2, 23.4, 11.3} 89. Photo diode is reverse biased because 1) Only one side is illuminated 2) Majority carriers flow under these conditions 3) Reverse current is small as compared to photo current 4) Reverse current is large as compared to photo current 16

15 90. Derivative control action is typically used when controlling, but rarely used when controlling 1) Temperature, Flow 2) Flow, Level 3) ph, Temperature 4) Level, Temperature 91. The acceptor level in a p-type semi conductor will be 1) closer to Fermi level 2) closer to conduction band 3) exactly at the centre of band gap 4) closer to valence band 92. The conduction electron is 1) valence electron in an atom 2) core electron in solid 3) free electron in solid 4) free electron in an atom 93. The I-V characteristics of the zener diodes D1 and D2 are shown in Figure I. These diodes are used in the circuit given in Figure II. If the supply voltage is varied from 0 to 100 V, then breakdown occurs in 1) D1 only 2) D2 only 3) Both D1 and D2 4) None of the above 94. Compare two p-n junctions, one with N A = N D = /cc and the other with N A = N D = /cc, which one of the following statements is TRU? 1) Reverse breakdown voltage is lower and depletion capacitance is lower 2) Reverse breakdown voltage is higher and depletion capacitance is lower 3) Reverse breakdown voltage is lower and depletion capacitance is higher 4) Reverse breakdown voltage is higher and depletion capacitance is higher 95. In a uniformly doped BJT, assume that N, NB and N C are the emitter, base and collector doping in atoms/cm 3, respectively. If the emitter injection efficiency of the BJT is close unity, which one of the following condition is TRU? 1) N N B NC 2) N N B and N B NC 3) N N B and N B NC 4) N N B NC 17

16 96. The input signal used with a JFT analog switch should be 1) small 2) large 3) a square wave 4) chopped 97. Thin gate oxide in a CMOS process in preferably grown using 1) wet oxidation 2) dry oxidation 3) epitaxial oxidation 4) ion implantation 98. The I-V characteristics of three types of diodes at the room temperature, made of semiconductors X, Y and Z, are shown in the figure. Assume that the diodes are uniformly doped and identical in all respects except their materials. If, and gz are the band gaps of X, Y and Z, respectively, then gx gy x X Y Z Y 1) gx gy gz 2) gx gy gz 3) gx gy gz 4) no relationship among these band gaps exists 99. A Silicon sample A is doped with atoms/cm 3 of boron. Another sample B of identical dimension is doped with atoms/cm 3 phosphorus. The ratio of electron to hole mobility is 3. The ratio of conductivity of the sample A to B is, 1) 3 2) 3) 2 3 4) A silicon wafer has 100 nm of oxide on it and is furnace at a temperature above 1000 C for further oxidation in dry oxygen. The oxidation rate 1) is independent of current oxide thickness and temperature 2) is independent of current oxide thickness but depends on temperature 3) slows down as the oxide grows 4) is zero as the existing oxide prevents further oxidation 18

17 ROUGH WORK 19

18 ROUGH WORK 20

OBJECTIVE TYPE QUESTIONS

OBJECTIVE TYPE QUESTIONS Q.1 The breakdown mechanism in a lightly doped p-n junction under reverse biased condition is called (A) avalanche breakdown. (B) zener breakdown. (C) breakdown by tunnelling.