Solution 4.6.5.5
If we close up the inner loop weget
G
equiv
=
1
1;G
1
Suppose we let G
1
be an opamp circuit with a gain of 0.99 Then the
denominator is
1;G
1
(s)=1;0:99 = 0:01
and
G
equiv
=
1
1;G
1
= 100:
Wehavethus used positivefeedbacktocreate a forward gain of100.
With the adventofopamps this trickisnolonger so important, but fty
years ago it provided a waytocreate a large gain.
1