User manual

Active Filter Demo Board Kit User’s Guide
DS51614A-page 16 © 2006 Microchip Technology Inc.
2.5.4 Multiple Feedback, Low-pass and Band-pass Filter Sections
TABLE 2-3: IMPEDANCES FOR MULTIPLE FEEDBACK, LOW-PASS AND
BAND-PASS FILTER SECTIONS
FIGURE 2-9: Multiple Feedback, Low-pass and Band-pass (modified) Filter
Topologies.
Topology MFB-LP1 MFB-LP2 MFB-BP2
Z
1
———
Z
2
———
Z
3
———
Z
4
0Ω 0Ω 0Ω
Z
5
———
Z
6
R11 R11 R11
Z
7
——R12
Z
8
—C12—
Z
9
R12 R12 C11
Z
10
0Ω R13 C12
Z
11
C11 C11 R13
U
1
R11
V
IN
V
OUT
V
DD
MFB-LP1
U
1
R11
V
IN
V
OUT
V
DD
MFB-LP2
R13
C12
C11R12
R12
C11
V
DD
/2
V
DD
/2
MFB-BP2
U
1
R11
V
IN
V
OUT
V
DD
C12
R13C11
R12
V
DD
/2