The closed loop transfer function of a negative feedback system is 10 and feedback factor is 0.05. What will be the open loop gain?

Question

Question

This question was previously asked in

HPCL Engineer Instrumentation 11 Aug 2021 Official Paper

Answer 1

Solution

Concept

The open loop gain is given by G(s)

The feedback factor is given by H(s)

Hence the closed loop transfer function is given by \(\frac{G(s)}{1+G(s)H(s)}\)

Calculation

Given \(\frac{G(s)}{1+G(s)H(s)}\) = 10

H(s) = 0.05

To claculate G(s) we have

\(\frac{G(s)}{1+G(s)0.05}\) = 10

G(s)= 10 + 0.5G(s)

0.5 G(s) = 10

G(s) = 20

Hence the open loop Gain is 20

Therefore the correct answer is option 2

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