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As shown in the figure, a negative feedback system has an amplifier of gain 100 with ±10% tolerance in
the forward path, and an attenuator of value 9 in the feedback path. The overall system 100
gain is approximately
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- 10 ± 1%
- 10 ± 2%
- 10 ± 5%
- 10 ± 10%
- 10 ± 1%
Correct Option: A
Gain, G(s) = 100 ± 10%
| H(s) = | ||
| 100 |
| = | |||
| R(s) | 1 + G(s) H(s) |
When G(s) = 100 + 10 = 110,
| = | = | ||||||
| R(s) | 1 + 90 × | 91 | |||||
| 100 | |||||||
= 9.89 ≈ 9.9
= 10 – 0.1 ≠ 10 – 1% of 10
Hence overall system gain = 10 ± 1%
