Electronics and Communication Engineering - Exam Questions Papers

41. 

A λ/4 long high frequency transmission line is terminated into one impedance ZR. If Z0 be the characteristic impedance of the line, then input impedance Zin is

A. ZoZR
B. Z2R/Zo
C. Z20/ZR
D. Infinity

Answer: Option C

Explanation:

, here and

[Here ZL = ZR].


42. 

Find the power absorbed or delivered by each source:

A. a = -32 b = - 12 c = -80 d = -60
B. a = -32 b = - 12 c = 80 d = 60
C. a = 32 b = 12 c = -80 d = 60
D. a = -32 b = 12 c = 80 d = -60

Answer: Option D

Explanation:

Source a : Power : 8 x (4) = - 32 W. Source A has delivered the power as it is. - ve.

Source b: Source B has absorbed power of + 12 W as power is positive

Source c: Source C has absorbed power of 5 x 16 = 80 W

Source d: Delivers power of 3 x ix x (5) = 3 x 4 x (- 5) = -60 W

Total power of the network is - 32 + 12 + 80 - 60 = 0 Watts.


43. 

The function shown in figure, can represent a probability density function for A __________

A. A = 1/4
B. A = 1/6
C. A = 1/9
D. A = 1/2

Answer: Option C

Explanation:

The condition for the probability density function d(x) isand is always non negative or the area under the curve f(x)is unity.

=> A x 6 +x 2 x 3A = 1

or 9A = 1 or A =.


44. 

If the transfer function of the following network is

The value of the load resistance RL is

A. R/4
B. R/2
C. R
D. 2R

Answer: Option C

Explanation:

.


45. 

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. 1.25 kΩ, 1.25 MΩ
B. 125 kΩ, 1.25 MΩ
C. 1.25 MΩ, 1.25 kΩ
D. 3.25 kΩ, 3.25 MΩ

Answer: Option A

Explanation:

80 = 20 log CMRR

CMRR = 10000

But CMRR = 2gmRE

= 1.25 MΩ

Adm = - gmRC

= 1.25 KΩ.