fier that produces the system output with a feedback signal derived
from the amplifier output. Both the amplifier characteristic and the
feedback characteristic are functions of frequency and are shown as
G(s) and H(s), respectively.
The performance of such system can be derived from an equation
that relates output to input. The equation is developed as follows:
1.
e
=
ec
–
ef
2.
eo
=
e
×
G(s)
3.
ef
=
eo
×
H(s)
4.
eo
=
G(s)
×
[
ec
–
eo
×
H(s)
]
5.
eo/ec
=
G(s)
/[1 +
G(s)
×
H(s
)] =
A
where
eo/ec
is the closed-loop system gain as a function of frequency.
If the feedback is disconnected from the summing junction, then
A
=
G(s)
×
H(s)
, the open-loop gain. Simple systems such as the one
shown ...
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