Texas Instruments DUAL-DIYAMP-EVM, User Manual

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+
±
+
±
C1
Z1/8
Z3/10
Z5/12
Z2/9
Z4/11
OUTA/B
V+
INA/B
REFA/B
R2/4 R1/3
VBA/B
V- C2
c _ REF
2/4 1/3 2/4
1
2 C R / /R
=
´ p ´ ´
f
Schematic and PCB Layout
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12 SBOU193 – July 2017
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DUAL-DIYAMP-EVM
For additional guidance in designing a filter, download FilterPro™ active filter design software.
Capacitor C2 for channel A and C4 for channel B provide the option to filter noise that may be introduced
from the REFA/B.
Equation 13 calculates the cut-off frequency due to C2/4.
(13)
Figure 16 displays the PCB layout of the top layer of the multiple feedback active filter circuit configuration.
Figure 16. Multiple Feedback Active Filter Top Layer PCB Layout
3.6 Sallen-Key Filter
Figure 17 displays the schematic for the Sallen-Key active filter circuit configuration.
Figure 17. Sallen-Key Active Filter Schematic
The Sallen-Key filter is one of the most commonly applied active filter topologies. The Sallen-Key filter can
be configured as a low-pass filter, high-pass filter, or band-pass filter based on the component selection of
Z1/8 through Z5/12.
Table 4 displays the type of passive components that should be chosen for Z1/8
through Z5/12 for each filter configuration.
Table 4. Sallen-Key Filter Component Type Selection
Pass-Band Filter
Type
Type of
Component (Z1/8)
Type of
Component (Z2/9)
Type of
Component (Z3/10)
Type of
Component (Z4/11)
Type of
Component (Z5/12)
Low Pass R1/8 R2/9 C3/10 Not Populated C5/12
High Pass C1/8 C2/9 R3/10 Not Populated R5/12
Band Pass R1/8 C2/9 R3/10 C4/11 R5/12