Datasheet

C
2
R
2
1
R
1
+ R
4
R
1
V
O2
V
IN
s
2
+ s
1
C
2
R
2
R
5
+ R
6
R
5
R
1
R
1
+ R
4
C
2
C
3
R
2
R
3
1
+
=
s
R
6
R
5
+ R
6
R
1
+ R
4
R
1
R
5
+ R
6
R
6
V
O1
V
IN
s
2
+ s
1
C
2
R
2
R
5
+ R
6
R
5
R
1
R
1
+ R
4
C
2
C
3
R
2
R
3
1
+
=
s
2
R
1
+ R
4
R
1
R
5
+ R
6
R
6
C
2
C
3
R
2
R
3
1
V
O
V
IN
s
2
+ s
1
C
2
R
2
R
5
+ R
6
R
5
R
1
R
1
+ R
4
C
2
C
3
R
2
R
3
1
+
=
V
O
= V
O2
-1
s C
3
R
3
V
O2
= V
O1
-1
s C
2
R
2
V
O1
=
-R
4
R
1
V
0
+
R
5
+ R
6
R
6
R
1
+ R
4
R
1
V
O2
R
5
+ R
6
R
5
R
1
+ R
4
R
1
V
IN
+
V
O1
V
O2
+
-
R
2
A
2
V
O
+
-
C
3
A
3
V
O2
C
2
R
3
SM73308
SNOSB90B –JUNE 2011–REVISED APRIL 2013 www.ti.com
For A
1
the relationship between input and output is:
(19)
This relationship depends on the output of all the filters. The input-output relationship for A
2
can be expressed
as:
(20)
And finally this relationship for A
3
is as follows:
(21)
Re-arranging these equations, one can find the relationship between V
O
and V
IN
(transfer function of the lowpass
filter), V
O1
and V
IN
(transfer function of the highpass filter), and V
O2
and V
IN
(transfer function of the bandpass
filter) These relationships are as follows:
Lowpass Filter
(22)
Highpass Filter
(23)
Bandpass Filter
(24)
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