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Electronics and Communication Engineering - Exam Questions Papers

Exercise : Exam Questions Papers - Exam Paper 4
36.
In the following transistor circuit VBE = 0. 7 V, rc = 25mV/IE, and β and the capacitance are very large

The value of DC current IE is
1 mA
2 mA
5 mA
10 mA
Answer: Option
Explanation:

Design is independent of IB as β is very high

IB ∼ 0

Thus applying Kirchhoff's law is base emitter, we get.

37.
A certain JK FF has tpd = 12 nsec. The largest MOD counter that can be constructed from these FFs and still operate up to 10 MHz is
any
8
256
10
Answer: Option
Explanation:

f0 = 107 Hz

⇒ 8.33

n = 8.

38.
A second-order system has a transfer function is given by . If the system, initially at rest is subjected to a unit step input at t = 0, the second peak in response will occur at :
p sec
p/3 sec
p/6 sec
p/2 sec
Answer: Option
Explanation:

Peak time

.

39.
Value of ZL for maximum power transfer is
R
R + jωL
R - jωL
None of these
Answer: Option
Explanation:

The value of load for maximum power transfer is given by complex conjugate of ZAB. ZAB = R + jXL = R + jωL.

∴ ZL for maximum power transfer is given by, ZL = R - jωL.

40.
A periodic voltage has following values for equal time intervals changing suddenly from one value to next : 0, 5, 10, 20, 50, 60, 50, 20, 10, 5, 0, - 5, - 10 etc.
RMS value of the waveform is :
31 v
32 v
insufficient data
none of these
Answer: Option
Explanation:

Mean value of V2 =

= 965 V

∴ rms value = ≈ 31 V.

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