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An amplifier has a gain of 1000 ± 10. Negative feedback is provided such that the gain variation is within 0.1%. Then the amount of feedback βf is:
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1 10 -
1 9 -
9 100 -
9 1000
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Correct Option: D
Given that A = 1000 ± 10
| = | = | = 0.01 | ||||
| A | 1000 | 100 |
| = 0.1% = | = 0.001 | |||
| Af | 100 |
Now, from relation
| = | x | |||||
| dA | (1 + Aβ) | A |
| 0.001 = | × 0.01 | |
| (1 + 1000 β) |
or 1 + 1000 β = 10
or 1000 β = 9
| or β = | ||
| 1000 |
Hence alternative (D) is the correct choice.
