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Electronics and Communication Engineering - Analog Electronics

Exercise : Analog Electronics - Section 5
41.
Which of the following can be used as a buffer amplifier?
CE
CC
CB
Both (a) and (c)
Answer: Option
Explanation:

Because of high input impedance and low output impedance, CC amplifier is suitable as buffer amplifier.

42.
The feedback technique employed in the following circuit is
voltage series feedback
current series feedback
voltage shunt feedback
current shunt feedback
Answer: Option
Explanation:

It is a voltage shunt feedback because output voltage is sampled and feedback current at the input side. The circuit can be redrawn as follows.

43.
A second order active bandpass filter can be obtained by cascading LP second order filter having higher cut off frequency fOH with a second order HP filter having lower cut off frequency fOL provided
fOL < fOH
fOL > fOH
fOH = fOL
fOH < 0.5 fOL
Answer: Option
Explanation:

If fOL is less than fOH, a passband will exist from fOL to fOH .

44.
In figure the approximate voltages of
base and emitter are - 8 V and - 7.3 V
base and collector are - 8 V and - 5 V
collector and emitter are - 5 V and - 7.3 V
base, emitter and collector are - 8, - 7.3 and - 5 V
Answer: Option
Explanation:

Base voltage = . Emitter voltage = - 8 + 0.7 = - 7.3 V.

45.
The open loop gain of an amplifier is 50 but likely to decrease by 20% due to various factors. If negative feedback with β = 0.1 is used, the change in gain will be about
20%
2%
0.5%
0.05%
Answer: Option
Explanation:

The stabilisation of gain is one of the advantages of closed loop system.

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