ACTIVE_FILTERS_Theory_and_Design

Sallen–Key Filters 39
C
C
2
1
C1
n
1.
924
= =
ISF × FSF 6π
× 10
C2n
0.
734
= =
ISF × FSF 6π
× 10
6
6
= 102
= 38.
9
nF
nF
R = ISF × R = 10 × 1 Ω=
10
n
4
k
R = ( K−1) R ∴ R = 5 kΩ
∴ R = 20 kΩ
b a a b
Figure 2.13a shows the designed filter, with its frequency response in Figure 2.13b.
Ω
39 n
10 K
R 1
C 2
10 K
+
R 2
−
102 n
C 1
20 K
LM741
R a
5 K
R b
(a)
20.00
10.00
Gain dB
0.00
–10.00
–20.00
–30.00
10 100
1 K
Frequency in Hz
(b)
10 K
FIGURE 2.13 (a) Second-order LP Chebyshev 3-db VCVS, f 1 = 300 Hz, K = 5; (b) its
frequency response.