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The gain margin in dBs of a unity feedback control system whose open-loop transfer function,  is

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  4. ∞ 

Answer (Detailed Solution Below)

Option 4 : ∞ 
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Detailed Solution

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Concept:

The gain margin is always calculated at the phase Crossover frequency (ωpc)

The phase Crossover frequency (ωpc) is calculated as:

Gain margin 

Calculation:

Given:

The phase Crossover frequency (ωpc) is calculated as:

Now,

Thus,

Gain margin 

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