ECE Paper - 2

1. Choose the correct one front among the alternatives A, B, C, D after matching an item from Group 1 with the most appropriate item, in Group2.


A. P-3, Q- 2, R-1
B. P-3, Q-1, R-2
C. P-2, Q-1, R-3
D. P-1, Q- 2, R-2
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2. Consider the following statements S1 and S2
S1: At the resonant frequency the impedance of a series R-L-C circuit is zero.
S2: In a parallel G-L-C circuit, increasing the conductance G results in increase in its Q factor.
Which one of the following is correct?

A. S1 is FALSE and S2 is TRUE
B. Both S1 and S2 are TRUE
C. S1 is TRUE and S2 is FALSE
D. Both S1 and S2 are FALSE
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3. A master-slave flip-flop has the characteristic that

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
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4. 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

A. 8/6
B. 12
C. 16
D. 8
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5. The drain of an n-channel MOSFET is shorted to the gate so that VGS = VDS. The threshold voltage (VT) of MOSFET is 1 V. If the drain current (ID) is 1 mA for VGS = 2V, then for VGS = 3V, ID is

A. 2 mA
B. 3 mA
C. 9 mA
D. 4 mA
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6. A 1 kHz sinusoidal signal is ideally sampled at 1500 samples/sec and the sampled signal is passed through an, ideal low-pass filter with cut-off frequency 800 Hz.The output signal has the frequency

A. zero Hz
B. 0.75 kHz
C. 0.5 kHz
D. 0.25 kHz
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7. Let A = 1111 1010, B = 0000 1010 be two 8-bit 2’s complement numbers. Their product in 2’s complement is:

A. 1100 0100
B. 1001 1100
C. 1010 0101
D. 1101 0101
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8. In a series of RLC circuit, R=10 ohm, L=100 mH, C=10 micro F. The selectivity of the circuit is:

A. 5
B. 1000 rad/sec
C. 15.92 Hz
D. 0.2
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9. The impulse response h[n] of a linear time-invariant system is given byh[n] = u[n + 3] + u[n - 2] - 2u[n-7]where u[n] is the unit step sequence. The above system is

A. stable but not causal
B. stable and causal
C. causal but unstable
D. unstable and not causal
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10. In what range should Re(s) remain so that the Laplace transform of the function e(a+2)t+5 exits?

A. Re (s) > a + 2
B. Re (s) > a + 7
C. Re (s) < 2
D. Re (s) > a + 5

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11. 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

A. 370 kHz
B. 190 kHz
C. 380 kHz
D. 95kHz
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12. The cascade amplifier is a multistage configuration of

A. CC-CB
B. CE-CB
C. CB-CC
D. CE-CC
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13. 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?

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
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14. In a full-wave rectifier using two ideal diodes, Vdc and Vm are the dc and peak values of the voltage respectively across a resistive load. If PIV is the peak inverse voltage of the diode, then the appropriate relationships for this rectifier are

A. Vdc = Vm/p, PIV = 2Vm
B. Vdc = 2 Vm/p, PIV = 2Vm
C. Vdc = 2 Vm/p, PIV = Vm
D. Vdc = Vm/p, PIV = Vm
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15. Choose the correct one from among the alternatives A, B, C, D after matching an item from Group 1 with the most appropriate item in Group 2.


A. 1-T, 2-P, 3-U, 4-S
B. 1-S, 2-U, 3-P, 4-T
C. 1-S, 2-P, 3-U, 4-Q
D. 1-U, 2-R, 3-S, 4-Q
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16. Consider an abrupt p-junction. Let Vbi be the built-in potential of this junction and VR be the applied reverse bias. If the junction capacitance (Cj) is 1 pF for
Vbi + VR = 1V, then for Vbi + VR - 4V, Cj will be

A. 4 pF
B. 2 pF
C. 0.25 pF
D. 0.5 pF
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17. A signal x(n) = sin(w0n + f ) is the input to a linear time-invariant system having a frequency response H(e^jw ). If the output of the system Ax(n - n0), then the most general form of ÐH(ejw) will be

A. - n0w0 + b for any arbitrary real b.
B. - n0w0 + 2pk for any arbitrary integer k.
C. n0w0 + 2pk for any arbitrary integer k.
D. -n0w0 f.
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18. Noise with uniform power spectral density of NW/Hz is passed through a filter H (w) = 2 exp(-jwtd) followed by an ideal low pass filter of bandwidth BHz. The output noise power in Watts is

A. 2NB
B. 4NB
C. eNB
D. 16 NB
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19. The state variable equations of a system are:
i. x1 = - 3×1 - x2 + u
ii. x1 = 2×1, y = x1 + u
The system is

A. controllable but not observable
B. observable but not controllable
C. neither controllable nor observable
D. controllable and observable
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20. A 1 mW video signal having a bandwidth of 100 MHz is transmitted to a receiver through a cable that has 40 dB loss. If the effective one-sided noise spectral density at the receiver is 10-20 Watt/Hz, then the signal-to-noise ratio at the receiver is

A. 50 dB
B. 30 dB
C. 40 dB
D. 60 dB
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Answers

1. B
2. D
3. C
4. C
5. D
6. C
7. A
8. D
9. A
10. A
11. C
12. B
13. D
14. B
15. C
16. D
17. B
18. B
19. D
20. A

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