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  1. The transfer function has a log-magnitude plot as shown below. Under the assumption that a minimum phase function, its transfer function is—


    1. 1
      1 + s

    2. 10
      1 + s

    3. 10
      s + 10

    4. 2
      s + 0.1
Correct Option: D

From figure transfer function is of the form

K
= (one pole)
(1 + sT)

as there is 20 dB/dec at
log ω = – 1
or
ω = 1/10
T = 1/ω = 10
Now, log |G| = 1
or
| G | = 10
or
K
= 10
(10ω)2 + 1

or
K
= 10
(10×1/10)2 + 1

or
K
= 10
2

k = 10√2
Now,
T.F. =
10√2
s·10 + 1

or
T.F. =
2
s + 0.1



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