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Schematic and PCB Layout
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16 SBOU191 – July 2017
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DIYAMP-SOT23-EVM
3.7 Dual-Supply, Multiple Feedback Filter
Figure 24 shows the schematic for the dual-supply, multiple feedback filter circuit configuration.
Figure 24. Dual-Supply, Multiple Feedback Filter Schematic
The MFB topology (sometimes called infinite gain or Rauch) is often preferred due to low sensitivity to
component variations. The MFB topology creates an inverting second-order stage. This inversion may, or
may not, be a concern in the filter application.
The dual-supply, MFB filter circuit can be configured as a low-pass filter, high-pass filter, or band-pass
filter based on the component selection of Z1 through Z5.
Table 5 displays the type of passive component
that should be chosen for Z1 through Z5 for each filter configuration.
Table 5. MFB Filter Type Component Selection
Pass-Band
Filter Type
Type of
Component (Z1)
Type of
Component (Z2)
Type of
Component (Z3)
Type of
Component (Z4)
Type of
Component (Z5)
Low Pass R1 C2 R3 R4 C5
High Pass C1 R2 C3 C4 R5
Band Pass R1 R2 C3 C4 R5
For additional guidance in designing a filter, download the FilterPro active filter design software.
The PCB layout of the top layer of the dual-supply, multiple feedback filter circuit configuration is displayed
in
Figure 25 .
Figure 25. Dual-Supply, Multiple Feedback Filter Top Layer