Datasheet

Application notes ST1CC40
14/37 DocID18279 Rev 5
Figure 6. Transconductance embedded error amplifier
R
C
and C
C
introduce a pole and a zero in the open loop gain. C
P
does not significantly affect
system stability but it is useful to reduce the noise at the output of the error amplifier.
The transfer function of the error amplifier and its compensation network is:
Equation 8
where A
vo
= G
m
· R
o
.
The poles of this transfer function are (if C
c
>> C
0
+ C
P
):
Equation 9
Equation 10
whereas the zero is defined as:
Equation 11


&
3
5
&
&
&
)%
&203
G9
5

*
P
G9
9

($
5
&
&
&
&
3
&

$0Y
A
0
s
A
V0
1s+ R
c
C
c

s
2
R
0
C
0
C
p
+R
c
C
c
sR
0
C
c
 R
0
C
0
C
p
+R
c
C
c
++1++ 
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------=
f
P LF
1
2  R
0
C
c
 
--------------------------------- -=
f
P HF
1
2  R
c
C
0
C
p
+ 
----------------------------------------------------=
F
Z
1
2  R
c
C
c
 
---------------------------------=