LS404 STMicroelectronics, LS404 Datasheet - Page 8

• Manufacturer Part Number: LS404
• Description: Low-noise bipolar op-amps
• Manufacturer: STMicroelectronics

LS404
In the circuit of figure 14, for fc = 3.4kHz and R
R1 = R2 = R3 = 10k , we obtain:
The attenuation of the filter is 30dB at 6.8kHz and
better than 60dB at 15kHz.
Table 2 : Damping Factor for Low-pass Butterworth Filters
Figure 15 : 5th Order High-pass Filter (Butterworth) with Unity Gain configuration
8/11
Order
2
3
4
5
6
7
8
Ci
C4 = 3.325
Ri
C1 = 0.421
C2 = 1.753
C3 = 0.309
Ci = 1.354
1.392
1.354
1.336
Ci
C1
--- -
R
1
--- -
R
1
--- -
R
--- -
R
--- -
R
1
1
1
----------- - = 15.14nF
2 fc
----------- - = 6.33nF
2 fc
----------- - = 1.97nF
2 fc
----------- - = 8.20nF
2 fc
----------- - = 1.45nF
2 fc
0.707
0.966
0.202
0.421
0.488
0.92
0.98
1
1
C1
1
1
1
C2
R1
1.035
1.41
3.54
1.08
1.75
1.53
1.02
C2
R2
0.309
0.707
0.623
0.38
0.83
C3
i
=
The same method, referring to table 2 and figure
15 is used to design high-pass filter. In this case
the damping factor is found by taking the recipro-
cal of the numbers in table 2. For fc = 5kHz and Ci
= C1 = C2 = C3 = 1nF we obtain:
3.235
1.414
1.604
2.61
1.20
C4
C3
R1 =
R2 =
Ri =
R3 =
R4 =
0.259
0.222
0.556
C5
-------------- -
0.354
-------------- -
0.421
-------------- -
1.753
-------------- -
0.309
-------------- -
3.325
1
1
1
1
C4
1
R3
--- -
C
1
--- -
C
--- -
C
3.86
4.49
1.80
1
1
--- -
C
1
--- -
C
C6
1
----------- - = 25.5k
2 fc
----------- - = 75.6k
2 fc
----------- - = 18.2k
2 fc
----------- - = 103k
2 fc
----------- - = 9.6k
2 fc
1
1
1
1
1
R4
0.195
C7
5.125
C8