MAX7490/MAX7491
Dual Universal Switched-Capacitor Filters
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Mode 2 Design Equations
Mode 2N
Figure 5 shows the configuration of Mode 2N. This
mode extends the topology of Mode 3A to Mode 2,
where the highpass and lowpass outputs are summed
through two external resistors, R
H
and R
L
, to create a
lowpass notch filter that has higher frequency than the
one in Mode 2. Mode 2 is most useful in lowpass elliptic
designs. When cascading the sections of the
MAX7490/MAX7491, the highpass and lowpass outputs
can be summed directly into the inverting input of the
next section. Only one external op amp is needed.
Mode 2N Design Equations
Figure 4. Mode 2, 2nd-Order Filter Providing a Highpass
Notch, Bandpass, and Lowpass Outputs
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