Question 8.13: An amplifier has an open-loop gain of 10,000. The open-loop ...
An amplifier has an open-loop gain of 10,000. The open-loop gain changes by 20 per cent due to ageing. Calculate the percentage change in the closed-loop gain for a feedback ratio of 0.1.
Taking,
\frac{dA}{A}=20 per cent
A = 10,000
β = 0.1
\frac{dA_{f}}{A_{f}}=\frac{dA}{A} ×\frac{1}{1+βA}
or, \frac{dA_{f}}{A_{f}}=\frac{20}{1+ 0.1 × 10,000}=\frac{20}{1001}=0.019 per cent
Therefore, the percentage change in the closed-loop gain is very small. This shows that negative feedback stabilizes the amplifier voltage gain.
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