Datasheet

V
I
V
O
C1
+
−
R
G
R
F
R1
f
–3dB
+
1
2pR1C1
V
O
V
I
+ ǒ1 )
R
F
R
G
Ǔ
ǒ
1
1 ) sR1C1
Ǔ
V
I
C2
R2R1
C1
R
F
R
G
R1 = R2 = R
C1 = C2 = C
Q = Peaking Factor
(Butterworth Q = 0.707)
(
=
1
Q
2 –
)
R
G
R
F
_
+
f
–3dB
+
1
2pRC
THS4031
THS4032
www.ti.com SLOS224G –JULY 1999–REVISED MARCH 2010
GENERAL CONFIGURATIONS
When receiving low-level signals, limiting the bandwidth of the incoming signals into the system is often required.
The simplest way to accomplish this is to place an RC filter at the noninverting terminal of the amplifer (see
Figure 58).
Figure 58. Single-Pole Low-Pass Filter
If even more attenuation is needed, a multiple-pole filter is required. The Sallen-Key filter can be used for this
task. For best results, the amplifier should have a bandwidth that is 8 to 10 times the filter frequency bandwidth.
Otherwise, phase shift of the amplifier can occur.
Figure 59. Two-Pole Low-Pass Sallen-Key Filter
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