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Schematic and PCB Layout
9 SBOU191 – July 2017
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DIYAMP-SOT23-EVM
3.3 Single-Supply, Sallen-Key Filter
Figure 12 shows the schematic for the single-supply, Sallen-Key filter circuit configuration.
Figure 12. Single-Supply, Sallen-Key Filter Schematic
Sallen-Key is one of the most commonly applied active filter topologies. The Sallen-Key is a non-inverting,
voltage-controlled, voltage-source (VCVS) able to attain larger Qs with a stable response than other filter
topologies. Because Sallen-Key is non-inverting, it might be preferable over the MFB topology.
The single-supply, Sallen-Key filter 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 4 displays the type of passive component
that should be chosen for Z1 through Z5 for each filter configuration.
Table 4. Sallen-Key Filter Component Type 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 R2 C3 C4 Not populated
High Pass C1 C2 R3 R4 Not populated
Band Pass R1 C2 R3 R4 C5
For additional guidance in designing a filter, download the FilterPro active filter design software.
The PCB layout of the top layer of the single-supply, Sallen-Key filter circuit configuration is displayed in
Figure 13 .
Figure 13. Single-Supply, Sallen-Key Filter Top Layer