In the feedback system shown in the given figure, the noise

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In the feedback system shown in the given figure, the noise component of output is given by (assume high loop gain at frequencies of interest)—

1. -N(s)
  H_1(s)
2. N(s)
  H_1(s)
3. N(s)
  H₁(s)H₂(s)
4. -N(s)
  H₁(s)H₂(s)

Correct Option: B

Let the noise component at the output be C_N (s) then
=

- G(s)H₂(s)N(s)1 - H₁(s).G(s)H₂(s)
(∴ R (s) = 0)

C_N(s)	=	- G(s)H₂(s)
N(s)	=	1 - H₁(s).G(s)H₂(s)

{∴ H₁(s) G(s) H₂(s) >> 1}

C_N(s)	=	1	or C_N(s) =	N(s)
N(s)	=	H₁(s)	or C_N(s) =	H₁(s)