Page 168 - Analog and Digital Filter Design

165
Highpass Filters

Also note that in the highpass biquad R5 is connected to a different node from
that used in the lowpass biquad.

Figure 5.18
The Biquad Filter

The following equations give component values. As in the case of the state
variable, the value of C can be chosen as any suitable value, then resistor values
calculated from the equations. First compute the section’s frequency from the
2
pole location: w,,Hp = 40Hp + wHpZ

1
R2=R3=-
W!,HPC
2cHPwnHPR
R5= 2
UnHP -wZHP
w, = the normalized zero frequency.
R6=AR