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Electronics & Communication papers 01 Questions And Answers Questions And Answers No. Question
1  The Boolean expression AC + B C
is equivalent to
Options  A) A
C + B C
+ AC  B) B
C + AC + B C
+  A
C B

C) AC + B C
+ B
C + ABC  D) ABC + A
B C
+ AB C
+ AB C

2  The resistivity of a uniformly doped n-type silicon sample is 0.5 W -cm. If the electron mobility ( m n) is 1250 cm 2 /V-sec and the charge of an electron is 1.6 x 10 -19 Coulomb, the donor impurity concentration (ND) in the sample is
Options  A) 2 x 10 16 /cm 3  B) 1 x 10 16 /cm 3
C) 2.5 x 10 15 /cm 3  D) 2 x 10 15 /cm 3

3  Consider the following statements S1 and S2.
S1: The  b  of a bipolar transistor reduces if the base width is increased.
S2: The  b of a bipolar transistor increases if the doping concentration in the base is increased. Which one of the following is correct?

Options  A) S1 is FALSE and S2 is TRUE   B) Both S1 and S2 are TRUE

C) Both S1 and S2 are FALSE   D) S1 is TRUE and S2 is FALSE

4  A system has poles at 0.01 Hz, 1 Hz and 80 Hz; zeros at 5 Hz, 100 Hz and 200 Hz. The approximate phase of the system-response at 20 Hz is

Options  A) - 90°  B) 0°
C) 90°   D) - 180°

5  In an abrupt p-n junction, the doping concentrations on the p-side and n-side are N A = 9x 10 16 /cm 3 and N D = 1 x 10 16 /cm 3 respectively. The p-n junction is reverse biased and the total depletion width is 3 m  m. The depletion width on the p-side is

Options  A) 2.7 m m   B) 0.3 m m.

C) 2.25 m m   D) 0.75 m m

6  A master-slave flip-flop has the characteristic that

Options  A) change in the input immediately reflected in the output
B) change in the output occurs when the state of the master is affected

C) change in the output occurs when the state of the slave is affected
D) both the master and the slave states are affected at the same time

7  A parallel plate air-filled capacitor has plate area of l0 -4 m 2 and plate separation of 10 -3 m. It is connected to a 0.5 V, 3.6 GHz source. The magnitude of the displacement current is ( e 0 = 1/36 p   x 10 -9 F/m)

Options  A) 10 mA  B) 100 mA
C) 10 A  D) 1.59 mA

8  The phase velocity of an electromagnetic wave propagating in a hollow metallic rectangular waveguide in the TE 10 mode is
Options  A) equal to its group velocity  B) less than the velocity of light in free space
C) equal to the velocity of light in free space  D) greater than the velocity of light in free space

9  Noise with uniform power spectral density of N 0 W/Hz is passed through a filter H ( w ) = 2 exp(-j w t d ) followed by an ideal low pass filter of bandwidth BHz. The output noise power in Watts is

Options  A) 2N 0 B   B) 4N 0 B

C) e N 0 B   D) 16 N 0 B

10  The cascade amplifier is a multistage configuration of
Options  A) CC-CB  B) CE-CB
C) CB-CC  D) CE-CC

11  Consider a lossless antenna with a directive gain of +6dB. If 1 mW of power is fed to it the total power radiated by the antenna will be
Options  A) 4 mW  B) 1 mW
C)
7 mW                                                        D) 1/4 mW

12  The bandgap of Silicon at room temperature is
Options  A) 1.3 eV  B) 0.7 eV
C) 1.1 eV  D) 1.4 eV

13  For a signal x(t) the fourier transform is X(f). Then the inverse Fourier transform of X(3f + 2) is given by
Options  A) 1
2
x ( t
2
) e (j3 p  t)  B) 1
3
x ( t
3
) e -j4 p t/3
C) 3x(3t)e -j4 p  t  D) x(3t+2)

14  In a PCM system, if the code word length is increased from 6 to 8 bits, the signal to quantization noise ratio improves by the factor

Options  A) 8/6   B) 12

C) 16   D) 8

15  Match the following and choose the correct combination:

Group 1  Group 2
E. Newton-Raphson method
F. Runge-kutta method
G. Simpson , s Rule
H. Gauss elimination  1. Solving nonlinear equations
2. Solving linear simultaneous equations
3. Solving ordinary differential equations
4. Numerical integration
5. Interpolation
6. Calculation of Eigenvalues

Options  A) E-6, F-1, G-5, H-3  B) E-1, F-6, G-4, H-3
C) E-1, F-3, G-4, H-2  D) E-5, F-3, G-4, H-1

16  The Fourier transform of a conjugate symmetric function is always

Options  A) imaginary   B) conjugate anti-symmetric

C) real  D) conjugate symmetric

17  Match the following and choose the correct combination.

Group 1  Group 2
E - continuous and aperiodic signal
F - continuous and periodic signal
G - Discrete and aperiodic signal
H - Discrete and periodic signal  1 - Fourier representation is continuous and aperiodic
2 - Fourier representation is discrete and aperiodic
3 - Fourier representation is continu-ous and periodic
4 - Fourier representation is discrete and periodic

Options  A) E - 3, F - 2, G - 4, H -1  B) E -1, F - 3, G - 2, H - 4
C) E -1, F - 2, G - 3, H - 4  D) E - 2, F - 1, G - 4, H - 3

18  A device with input x(t) and output y(t) is characterized by:   y(t) = x 2 (t).
An FM signal with frequency deviation of 90 kHz and modulating signal bandwidth of 5 kHz is applied to this device. The bandwidth of the output signal is

Options  A) 370 kHz    B) 190 kHz
C) 380kHz   D) 95kHz

19  For the polynomial P(s) = s 5   + s 4 + 2s 3 + 2s 2 + 3s + 15, the number of roots which lie in the right half of the s-plane is

Options  A) 4  B) 2
C) 3  D) 1