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High-Pass Filter Design
With C 1 = 330 pF and C 2 = 4.7 nF, the values for R1 and R2 are:
R 1 = 1.45 kΩ, with the closest 1% value being 1.47 kΩ
R 2 = 4.51 kΩ, with the closest 1% value being 4.53 kΩ
Figure 16–22 shows the final filter circuit with its partial filter stages.
3.16k
V IN
1.87k 4.42k
1n
820p
1.5n
1.47k 4.53k
330p
4.7n
V OUT
Figure 16–22.
Fifth-Order Unity-Gain Butterworth Low-Pass Filter
16.4 High-Pass Filter Design
By replacing the resistors of a low-pass filter with capacitors, and its capacitors with resistors,
a high-pass filter is created.
V IN
C 2
R 1
R 2
C 1
C 2
V OUT
V IN
C 1
V OUT
R 1
R 2
Figure 16–23.
Low-Pass to High-Pass Transition Through Components Exchange
To plot the gain response of a high-pass filter, mirror the gain response of a low-pass filter
at the corner frequency, Ω=1, thus replacing Ω with 1/Ω and S with 1/S in Equation 16–1.
Active Filter Design Techniques
16-21