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CAPACITORLESS_NOTCH_FILTER

2017-02-27 06:49  
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CAPACITORLESS_NOTCH_FILTER
The notch frequency for the filter is set by fnotch+[(ALP/AHP)×(RZ2/RZ1)]×f0where ALP and AHP are the gain from input to low-pass output at f=0 Hz,and the gain from input to high-pass output at f≤f0,respectively. Typically ((ALP/AHP)×(RZ2/RZ1)=1;therefore,fnotch=f0,and is gtven by f0=1/(2π)(RFC)where RF=RF1=RF2, and C=C1=C2. The -3-dB bandwidth is determined by the following relation∶BW-3dB=fnotch/Q, where BW-3dB=fH-fL. The Q of the filter affects the passband gainc(which should be adjusted to unity) and is related to the ratio of the resistances RZ3 to RZ1 and RZ3 to RZ2. In other words,Q=(RZ3/RZ1)=(RZ3/RZ2). Q also is related to RQ by the follOwing relation∶RQ=(25 kΩ/Q-1).