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Band-Pass Filter Design
R 1
1
1
2f c a 1
C 1 2·10 3 Hz·0.756·100·10 9 2.105 k
F
Closest 1% value is 2.1 kΩ.
Second Filter
With C = 100nF,
R 1
1
f c Ca 1
Closest 1% value is 3.16 kΩ.
R 2
a 1
4f c Cb 1
Closest 1% value is 1.65 kΩ.
Figure 16–30 shows the final filter circuit.
1
3.18 k
·103·100·109·0.756 0.9996
1.67 k
4·103·100·109·0.4772 V IN
100n
100n
100n
1.65k
2.10k
3.16k
V OUT
Figure 16–30.
Third-Order Unity-Gain Bessel High-Pass
16.5 Band-Pass Filter Design
In Section 16.4, a high-pass response was generated by replacing the term S in the lowpass
transfer function with the transformation 1/S. Likewise, a band-pass characteristic
is generated by replacing the S term with the transformation:
1 s 1
s
(16–7)
In this case, the passband characteristic of a low-pass filter is transformed into the upper
passband half of a band-pass filter. The upper passband is then mirrored at the mid frequency,
f m (Ω=1), into the lower passband half.
Active Filter Design Techniques
16-27