
Ampliers: Cascading Stages
509
,
,
,12, ,
,
=−
+
i
R
RR h
i
oI
CI
CI II ie II
cI
cI fe IbI
,
i
i
bI
I
IieI
g,
12,
12
=
+
we can nally write
,
,
,
12,
12,,
,
,12, ,
,
12,
12
=
++
A
RR
h
Rh
RR h
h
Rh
i
CII
CIIL
fe II
II
II ie II
CI
CI II ie II
fe I
I
IieI
14.4.3 AC Voltage Gain
The overall voltage gain is dened as
def
,
A
v
vII
l
. It depends on the voltage gain of
each stage.
The voltage gain of the second stage is
A
v
v
vII
oII
ce II
,
,
,
It is easy to demonstrate that
i
i
o
CII
cII
,
,
=−
+
,,,, ,,
==−=−vv RRiRRh i
ce II oCII LcII CIILfe II bII
The voltage gain of the second stage is then the ratio of hybrid parameters times
the load resista ...