Electronics and Communication Engineering - Exam Questions Papers

16. 

A message signal x(t) is amplitude modulated with carrier c(t).
x(t) = 2 sin 600pt
c(t) = 8 cos (2p x 106 t)
such that the modulated signal is
(8 + 2 sin 600pt) [cos 2p x 106 t]
The total side band power is:

A.
B.
C.
D. 0.5ω

Answer: Option C

Explanation:

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17. 

The cross section of a JFET is shown in the following figure. Let Va be - 2 V and let Vp be the initial pinch-off voltage. If the width W is doubled (with other geometrical parameters and doping levels remaining the same), then the ratio between the mutual transconductances of the initial and the modified JFET is

A. 4
B.
C.
D.

Answer: Option C

Explanation:

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18. 

Simplify : A + B + A B + (A + B)AB + C(B + AB)

A. B + A
B. C
C. C
D. 1

Answer: Option A

Explanation:

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19. 

Which one of the following driving point functions does not represent an LC network?

A.
B.
C.
D.

Answer: Option A

Explanation:

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20. 

A 2 μF capacitor is shunted by a 1 kΩ maintained at temperature 400 K. The rms noise voltage across the capacitor over the entire frequency band is:

A. 6.25 x 10-8 V
B. 5.25 x 10-6 V
C. 6.25 x 10-6 V
D. 5.25 x 10-8 V

Answer: Option D

Explanation:

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