ELEX

- 1. A MOSFET has a threshold voltage of 1 V and oxide thickness of 500 x 10
^{-8}[εr = 3.9; ε0 = 8.85 x 10^{-14}F/cm, q = 1.6 x 10^{-19}c]. The region under the gate is ion implanted for threshold voltage tailoring. The base and type of impant required to shift threshold voltage to - 1 V are __________ .
A) 0.86 x 10 ^{9}/cm2, p-typeB) 8.6 x 10 ^{11}/cm2, n-typeC) 8.6 x 10 ^{11}/cm2, p-typeD) 1.02 x 10 ^{12}/cm2, n-type- 2. In a semiconductor material. The hole concentration is found to be 2 x 2.5 x 10
^{15}cm^{-3.}If mobility of carriers is 0.13 m^{2}/ v-s. Then find the current density if electric field intensity is 3.62 x 10^{-19}
A) 7.6237 x 10 ^{-3} A/cm^{2}B) all of these C) 7.6237 x 10 ^{-5} A/cm^{2}D) 7.6237 x 10 ^{-4} A/cm^{2}- 3. In a 4 bit weighted resistor D/A converter, the resistor value corresponding to LSB is 32 kΩ. The resistor value corresponding to MSB will be
A) 32 KΩ B) 16 KΩ C) 8 KΩ D) 4 KΩ - 4. As the temperature increases the mobility of electrons __________ .
A) decreases because the number of carries increases with increased collisions B) increases because the number of carries decreases with decreased collisions C) increases because the number of carries decreases with decreased collisions D) change slighly - 5. "Consider the following:
1.) Maximum energy of electrons liberated photoelectrically is independent of light intensity 2.)Maximum energy of electrons liberated photoelectrically varies nonlinearly with frequency of incident light."
A) (1) and (2) both are true B) (1) and (2) both are false C) (1) is false and (2) is true D) (1) is true and (2) is false - 6. The gradient of any scalar field always yields __________ .
A) an irrotational field B) a solenoidal field C) all of these D) a conservative field - 7. In a flash type ADC, employing 15 comparators resolution with 10 volts reference; is expected to be :
A) insufficient data B) 0.525 V C) 0.625 V D) 0.656 V - 8. Consider a unity feedback control system with open-loop transfer function G(s) = K/(s(s+1)) The steady state error of the system due to a unity step input is :
A) infinite B) 1/K C) 0 D) K - 9. The specific gravity of tungsten is 13.8 and its atomic weight is 184.0 Assume that there are two free elements per atom. Then the Fermi level or characteristic energy for the crystal in eV will be
A) -7.326 eV B) -8.95 eV C) 8.95 eV D) 7.326 eV - 10. For a given voltage, four heating coils will produce maximum heat when connected
A) one pair in parallel with the other two in series B) all in series C) all in parallel D) with two parallel pairs in series - 11. A n-channel JFET has IDSS = 2 mA, Gate to source voltage VGS = - 2 V and trans-conductance is 0.5 mW then pinch-off voltage is __________ .
A) 2V B) -4V C) -2V D) 4V - 12. "For a series resonant circuit at low frequency circuit impedance is __________ and at high frequency circuit impedance is __________
Fill in the blanks respectively"
A) inductive, capacitive B) capacitive, resistive C) capacitive, inductive D) resistive, inductive - 13. A signal with ± 10 V ranged and 1 KHz band width is being digitized using a sample and hold circuit and a 10 bit quantizer. The minimum sampling rate is :
A) 3115.95 V/sec B) 31415.95 V/sec C) 62831.9 V/sec D) 125663.8 V/sec - 14. A tachometer has a sensitivity of 4 V/1000 rpm. Express the gain constant of the tachometer in the units volts/(rad/sec).
A) 1 B) 0.0381 C) 0.0489 D) 2 - 15. The steady state error of a stable type 0 unity feedback system for a unit step function is :
A) 1/(1+kp) B) 1/kp C) 0 D) infinity - 16. The current i(t) through a 10 Ω resistor in series with an inductance is given by i(t) = 3 + 4 sin (100t + 45°) + 4 sin (300t + 60°) Amperes. The RMS value of the current and the power dissipated in the circuit are
A) sqrt(11) A, 1210 W respectively B) sqrt(41) A, 410 W respectively C) 5 A, 250 W respectively D) sqrt(35) A, 350 W respectively - 17. The cut off voltage for JFET is 5 V. The pinch off voltage is __________ .
A) 2.5V B) 1/5V C) (5.0) ^{1}/2D) 5V - 18. The resolution of a 4 bit counting ADC is 0.5 volts. For an analog input of 6.6 volts, the digital output of the ADC will be
A) 1110 B) 1010 C) 1000 D) 101 - 19. The maximum percent overshoot with maximum value of first overshoot as 3.5 V and steady state value as 2.575 V is
A) 35.92% B) 26.43% C) 57.61% D) 15.24% - 20. Let f(A, B) = A ⊕ B; then the simplified form of the function f(f(x ⊕ y, z)w) is
A) x ⊕ y ⊕ z ⊕ w B) (x ⊕ y ⊕ z) + w C) none of these D) (x ⊕ y ⊕ z)w - 21. If the memory chip size is 256 x 1 bits, then the number of chips required to make up 1 kB (1024) bytes of memory is
A) 12 B) 8 C) 32 D) 24 - 22. A coil has a designed for high Q performance at a rated voltage and a specified frequency. If the frequency of operation is doubled, and the coil is operated at the same rated voltage, then the Q factor and the active power P consumed by the coil will be affected as follows.
A) P decreases 4 times, Q is doubled B) P remains constant, Q is doubled C) P is halved, Q is doubled D) P is doubled, Q is halved - 23. The number of variables in a function is odd and the number of minterms with even number of 0's are same as the number of minterms with odd number at 1 's, the expression formed can be represented in __________ as well as __________ form.
A) OR, exclusive - OR B) equivalence, exclusive - OR C) AND, coincidence D) exclusive - OR, NOR - 24. A bipolar differential amplifier uses a transistor having β0 = 200, ICQ = 100 mA, |Adm| = 500 and CMRR = 80 dB. The value of Rc and RE will be respectively __________ .
A) 125 kΩ, 1.25 MΩ B) 1.25 kΩ, 1.25 MΩ C) 1.25 MΩ, 1.25 kΩ D) 3.25 kΩ, 3.25 MΩ - 25. A ramp input applied to a unity feedback system results in 5% steady state error. The type number and zero frequency gain of the system are respectively.
A) 1 and 20 B) 0 and 1/20 C) 0 and 20 D) 1 and 1/20 - 26. "Which of the following terms are equivalent?
1.) A ⊕ B ⊕ C 2.) A ⊕ B ⊙ C 3.) A ⊙ B ⊕ C 4.) A ⊙ B ⊙ C"
A) 1 and 3 B) 2 and 3 C) 1 and 4; 2 and 3 D) 1, 2 and 4 - 27. The input 3-dB frequency is :
A) 1010 Hz B) 148 Hz C) 100 Hz D) 100 kHz - 28. When transient and steady state response require improvement; a __________ is used.
A) Integrator B) Lag - Lead compensator C) Lead compensator D) Lag compensator - 29. 2's complement representation of a 16 bit number (one sign bit and 15 magnitude bits) is FFFF. Its magnitude in decimal representation is
A) 32,767 B) 65,535 C) 0 D) 1 - 30. A certain JK FF has tpd = 12 nsec. The largest MOD counter that can be constructed from these FFs and still operate up to 10 MHz is
A) 10 B) 8 C) 256 D) any - 31. Using 4-bit numbers (n = 4) if k = (0011)2 how is k expressed in 2's complement.
A) (1100)2 B) (1011)2 C) (1101)2 D) (0101)2 - 32. Which factor determines whether the medium is free space, lossless dielectric, lossy dielectric or good conductor?
A) Reflection coefficient B) Loss tangent C) Constitutive parameters (σ, μ, ε) D) Attenuation constant - 33. "Consider the following program segment written for 8085 based system
LXI SP, FFFFH MVI A, FFH MOV BB, A K: DCR B PUSH HL JNZ K INR A LXI H, FFCEH CPI 20H LHLD The contents of accumulator is :"
A) 20 B) indeterminate C) CE D) FE - 34. In a JK flip-flop, J is connected to Q and K is connected to Q outputs. The JK FF converts into a
A) T FF B) D FF C) RS FF D) Clocked RS FF - 35. A point charge of 6 μC is located at the origin, uniform line charge density of 180 nC/m of 8 m length lies along the x axis and a uniform sheet of charge equal to 25 nC/m
^{2}of area pi x 4^{2}lies in the z = 0 plane. Calculate total electric flux leaving the surface of sphere of 4 m radius centered at origin.
A) 8.697 μC B) 86.97 μC C) 8.697 nC D) 86.97 nC - 36. Input and output impedance with feedback for voltage series feedback having A = -200, R1 = 10 kΩ, R0 = 50 kΩ and feedback factor β = -0.2 will be
A) ≈ 0.243 kΩ, 2050 kΩ B) 410 kΩ, 2050 kΩ C) 410 kΩ, 1.219 kΩ D) ≈ 0.24 kΩ, 1.219 kΩ - 37. It is desired to design a phase shift oscillator using an FET having a gm = 5000 μSiemen, rd = 40 kΩ and feedback circuit value of R = 10 K. Then value of C for oscillator operation at 1 kHz and that of RD for A = 40 to ensure oscillator action are
A) 6.4 nF, 80 K B) 65 pF, 80 K C) 6.5 pF, 10 K D) 6.5 nF, 10 K - 38. "Consider following statements :
1.) Maximum energy of electrons liberated photoelectrically is independent of light intensity 2.) Maximum energy of electrons liberated photoelectrically varies nonlinearly with frequency of incident light."
A) statement (1) and (2) both are false B) statement (1) is false and (2) is true C) statement (1) is true and (2) is false D) statement (1) and (2) both are true - 39. The fourier transform of a voltage signal x(t) is X(f). The unit of X(f) is __________ .
A) volt ^{2}B) volts C) volt-sec D) volt/sec - 40. The inconsistency of Ampere's law can be removed by adding __________ to it.
A) conduction current density alone. B) displacement current density alone. C) all of these D) displacement and conduction current densities. - 41. Consider a parallel plate capacitor being charged. Identify the incorrect statements
A) Rate at which energy flows into this volume is equal to the integration of the Poynting vector over the boundary of the volume between the plates. B) The Poynting vector points everywhere radially into the volume between the plates. C) Energy stored in the capacitor does not enter it through the connecting wires but through the space around the wires and plates uf capacitor D) The Poynting vector points everywhere radially outward of the volume between the plates - 42. The ratio of condition current density to displacement current density for a good conductor and a good dielectric is respectively __________ .
A) less than 1, less than 1 B) greater than 1, greater than 1 C) greater than 1, less than 1 D) all equal to 1 - 43. A 'n' bit sequence generator employing SR flip-flop has maximum length of the sequence as :
A) n B) 2 ^{n}C) 2 ^{n - 1}D) 2 ^{n} - 1- 44. A speech signal, band limited to 4kHz and peak voltage varying between + 5V and - 5V is sampled at the Nyquist rate. Each sample is quantized and represented by 8 bits. The number of quantization levels required to reduce the quantization noise by a factor of 4 would be
A) 512 B) 64 C) 256 D) 1024 - 45. A speech signal, band limited to 4kHz and peak voltage varying between + 5V and - 5V is sampled at the Nyquist rate. Each sample is quantized and represented by 8 bits. Assuming the signal to be uniformly distributed between its peak values, the signal to noise ratio at the quantizer output is
A) 156dB B) 48dB C) 64dB D) 32dB - 46. The drain current of a MOSFET in saturation is given by lp = K(VGS - VT)
^{2}where K is a constant. The magnitude of the transconductance gm is
A) 2K (VGS - VT) B) K (VGS - VT) ^{2}/(Vgs)C) Id/(Vgs-Vds) D) K (VGS - VT) ^{2}/(Vds)- 47. A uniform plane wave is described by the equation H = 2e
^{j0.1piz}ay A/m. If the velocity of the wave is 2 x 10^{8}m/s and εr = 1.8, then. The electric field intensity is
A) 903.5e ^{-j0.1pz} v/mB) 903.5e ^{-j0.1px} v/mC) 90.35e ^{-j0.1px} v/mD) 90.35e ^{-j0.1pz} v/m- 48. "A silicon PN junction with no bias have a doping concentration of
Nd = 2 x 10^{16}cm^{-3}and Na = 10^{16}cm^{-3.}The space charge width is:"
A) 3.345 x 10 ^{-3} cmB) 3.345 x 10 ^{-6} cmC) 3.345 x 10 ^{-4} cmD) 3.345 x 10 ^{-5} cm- 49. In 8085, Whenever a signal is received at TRAP terminal its program execution is transferred to a subroutine on address __________ .
A) 002 CH B) provided by the address generation logic C) 0000 H D) 0024 H - 50. In n-well CMOS fabrication substrate is:
A) heavily doped n-type B) lightly doped n-type C) lightly doped p-type D) heavily doped p-type - 51. "The following statements are true with respect to
*Cascode Amplifier*. 1.) The reduction in h12 and Miller capacitance result in negligible reverse internal feedback. 2.) A's is large loads cannot be connected. 3.) As a narrow band amplifier, it provides small range of cμ is reduced. 4.) As a narrow band amplifier it provides small range of frequencies parameters the effect of cμ reduces."
A) only 1 and 4 B) only 2 and 4 C) only 1 D) only 1 and 3 - 52. For a bipolar transistor, avalanche multiplication factor depends on __________ .
A) Vcb B) Vbe C) Vce D) Vee - 53. For a class B amplifier using a supply of VCC = 30 V and driving a load of 16 Ω the maximum efficiency will be __________ .
A) 72.40% B) 68.54% C) 78.54% D) 62.40% - 54. Find the electric charge required on the earth and moon to balance their gravitational attraction if the charge on the earth is 10 times that on the moon.
A) 17.3 GC B) 1.73 GC C) 1.73 TC D) 17.3 TC - 55. A Hartley oscillator uses FET with gm of 2 ms and rd = 2 KΩ. The total coil inductance is 10 μH with turns ratio of input to output side of 1 : 10. It is tuned with a 50 pf capacitor. Find frequency of oscillations, amplifier gain margin in dB.
A) 7.4 MHz, 13 dB B) 6.93 MHz, 12.9 dB C) 7.3 MHz, 14.1 dB D) 7.11 MHz, 13.97 dB - 56. The surface charge density on a conductor is 1.55 x 10
^{-9}C/m^{2.}The conductor is immersed in water with ε = 78ε0.The electric field will be __________ .
A) 2.25 V/m B) 3 V/m C) 2 V/m D) 1.55 V/m - 57. A 16 bit type ADC uses 1 MHz clock its maximum conversion time is __________ .
A) 66 ms B) 15 ms C) 6.5 ms D) 16 μs - 58. Which of the following equations satisfy Maxwell's equations?
A) Fy = cos (y - ct), Ex = Ez = 0 Bx = cos(y - ct), By = Bz = 0 B) Ex = Ey = 0, Ez = cos (y - ct) Bx = cos(y - ct), By = Bz = 0 C) Ex = Ey = 0, Ez = cos (y- ct) By = cos(y - ct), Bx = Bz = 0 D) all of these - 59. Conversion rate, for a successive approximation ADC which uses 2 MHz clock and 5 bit binary ladder containing 8 VV reference voltage is __________ .
A) 64516.12 conversions/sec B) 2.5 bps C) 400000 bps D) 400000 conversions/sec - 60. The electric field of uniform plane wave is given by E = 20 sin (2 p x 10
^{8}t- piz) ax + 20 cos (2 p x 10^{8}t - piz) ay. The polarization of wave is
A) Circular, left handed B) Circular, right handed C) Elliptical, right handed D) Elliptical, left handed - 61. "Consider the following statements a half adder.
1.) As a half subtractor also 2.) has two outputs CH = x x y and Sn = x ⊕ y for two inputs x and y 3.) has two outputs CH = x + y and SH = x ⊕ y for two inputs x and y 4.) is a combinational circuit Which of the statements given above is/are correct?"
A) 1, 3, 4 B) 4 only C) 2 and 3 D) 1, 2, 4 - 62. The number of distinct Boolean expressions of 3 variables is
A) 256 B) 8 C) 64 D) 7 - 63. A series RLC circuit has a resonance frequency of 1 kHz and a quality factor Q = 100. If each of R, L and C is doubled from its original value, the new Q of the circuit is
A) 100 B) 50 C) 25 D) 200 - 64. A generator of 50 Ω internal impedance and operating at 1 GHz feeds a 75 Ω load via a coaxial line of characteristic impedance 50 Ω. The VSWR on the feed line is
A) 1.5 B) 0.5 C) 1.75 D) 2.5 - 65. "I. Hall coefficient RH is directly proportional to the charge density
II. RH depends upon type of the semiconductor material (n - type or p - type) III. Hall co-efficient RH is directly proportional to hall voltage VH From the above statements which are the false statements?"
A) II only B) all of the these C) I only D) III only - 66. In a series operated thyristor configuration, each thyristor should support 100 V. However, the three thyristors only support voltage of 100 V, 90 V and 85 V respectively. Hence, the string efficiency in the case is :
A) 69.42% B) 45.84% C) 98.45% D) 91.67% - 67. A uniform plane wave in the free space is normally incident on an infinitely thick dielectric slab (dielectric constant εr = 9). The magnitude of the reflection coefficient is
A) 0 B) 0.3 C) 0.8 D) 0.5 - 68. If each stage has a gain of 10 dB and noise figure of 10 dB, then the overall noise figure of a two stage cascade amplifier will be
A) 10 B) 1 C) 1.09 D) 10.9 - 69. Using 4-bit numbers (n = 4) if k = (0011)2, how is k expressed in 2's complement?
A) (1011)2 B) (1100)2 C) (0101)2 D) (1101)2 - 70. The number of variables in a function is odd and the number of minterms with even number of 0's are same as the number of minterms with odd number at 1's, the expression formed can be represented in __________ as well as __________ form.
A) OR, Ex - OR B) Equivalence, Ex - OR C) AND, Coincidence D) Ex - OR, NOR - 71. The electric field of uniform plane wave is given by E = 20 sin (2 pi x 10
^{8}t- pz) ax + 20 cos (2 pi x 10^{8}t - pz) ay. Find phase velocity
A) 2/pi x 108 m/s B) 2pi x 108 m/s C) pi x 108 m/s D) 2 x 10 ^{8} m/s- 72. A conductor in x-y plane and having length 1 m is moving with a velocity V = (2i + 3j + k) m/sec. A magnetic induction field B = (i + 2j) Wb/m
^{2}is applied to the conductor. The potential difference between the ends of the conductor is
A) 0V B) 4.88 V C) sqrt(6) V D) 5V - 73. The two numbers represent in signed 2's complement form are P = 11101101 and Q = 111001110. If Q subtracted from P, the value obtained in signed 2's complement form is
A) 100000111 B) 111 C) 111111001 D) 11111001 - 74. A switch tail ring counter is made by using a single D FF. The resulting circuit is a
A) JK FF B) SR FF C) D FF D) T FF - 75. In a synchro error detector, the output voltage is proportional to [ω(t)]n, where ω(t) is the rotor velocity and n equals :
A) 1 B) -2 C) 2 D) -1 |

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