Electronics and Communication Engineering - Exam Questions Papers

21. 

The time constant of the network shown in figure is

A. 2 RC
B. 5/3 RC
C. RC/2
D. None of these

Answer: Option B

Explanation:

Req = (R || 2R) + R

.


22. 

For the 8085 assembly language program given below, the content of the accumulator after the execution of the program is

A. 00H
B. 45H
C. 67H
D. E7H

Answer: Option C

Explanation:

A → 0100 0101

B → 0100 0101

Carry flag → 0

RAR will A → 0010 0010

XRA B 0110 0111

67.


23. 

Consider the following BJT circuit:
hie = 2 k ohm
hfe = 100
hre = 2.5 x 10-4

The value of Ri is :

A. 2.46 kΩ
B. 2.88 kΩ
C. 200 Ω
D. 18.48 Ω

Answer: Option A

Explanation:

Ri = 7 || 4.3 || (2 + (1 + 100)330) = 2.88 kΩ.


24. 

One of a loss-less transmission line having the characteristic impedance of 75 Ω and length of 1cm is short-circuit. At 3 GHz, the input impedance at the other end of the transmission line is

A. 0
B. resistive
C. capacitance
D. inductive

Answer: Option D

Explanation:

X = 10 cm, ZL = 0, βl =

Thus Zin is Z0which is inductive.


25. 

. The signal is __________ .

A. periodic for t > 0
B. non-periodic
C. periodic for t < 0
D. depends on t

Answer: Option B

Explanation:

for

for periodicity should be a rational number.

But our case not a rational number.

Hence non periodic.