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Electronics and Communication Engineering - Analog Electronics

Exercise : Analog Electronics - Section 1
6.
An RC coupled amplifier has an open loop gain of 200 and a lower cutoff frequency of 50 Hz. If negative feedback with β = 0.1 is used, the lower cut off frequency will be
about 50 Hz
about 5 Hz
about 2.38 Hz
about 70.5 Hz
Answer: Option
Explanation:

New lower cutoff frequency = .

7.
In figure v1 = 8 V and v2 = 4 V. Which diode will conduct?
D2 only
D1 only
Both D1 and D2
Neither D1 nor D2
Answer: Option
Explanation:

D1 will conduct and the output voltage will be about 7 V. Therefore D2 will be reverse biased and will not conduct.

8.
The load impedance ZL of a CE amplifier has R and L in series. The phase difference between output and input will be
180°
0
more than 90° but less than 180°
more than 180° but less than 270°
Answer: Option
Explanation:

It is 180° for purely resistive load and between 180° and 270° for R-L load.

9.
Gain of the amplifier is 'A'. Then the I/P impedance and O/P impedance of the closed loop amplifier shown below would be
Answer: Option
Explanation:

By using Miller theorem circuit can be redrawn as

.

10.
If an amplifier with gain of - 1000 and feedback factor β = - 0.1 had a gain change of 20% due to temperature, the change in gain of the feedback amplifier would be
10%
5%
0.2%
0.01%
Answer: Option
Explanation:

As we know, Gain with feedback

A = - 1000, β = -0.1 .

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