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Question 7.4: If, in Example 7.3, the amplifier’s open-loop voltage gain i...

If, in Example 7.3, the amplifier’s open-loop voltage gain increases by 20%, determine the percentage increase in overall voltage gain.

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The new value of voltage gain will be given by:

A_v = A_v + 0.2 A_v = 1.2 × 50 = 60

The overall voltage gain with negative feedback will then be:

G=\frac{A_v}{1+\beta A_v}=\frac{60}{1+(0.1\times 60)} =\frac{60}{7} =7.14

The increase in overall voltage gain, expressed as a percentage, will thus be:

\frac{8.57-8.33}{8.33} \times  100 %=2.88%

Note that this example illustrates one of the important benefits of negative feedback in stabilizing the overall gain of an amplifier stage.

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