TLV2371-Q1, TLV2372-Q1, TLV2374-Q1
FAMILY OF 550-μA/Ch 3-MHz RAIL-TO-RAIL INPUT/OUTPUT
OPERATIONAL AMPLIFIERS
SGLS244A − MAY 2004 − REVISED JUNE 2008
APPLICATION INFORMATION
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 amplifier
(see Figure 30).
R
R
F
G
V
DD
/2
−
+
V
1
O
V
I
R1
C1
f
+
–3dB
2pR1C1
V
R
O
F
1
ǒ
1 ) sR1C1Ǔ
+
ǒ
1 )
Ǔ
V
R
I
G
Figure 30. 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.
Failure to do this can result in phase shift of the amplifier.
C1
R1 = R2 = R
C1 = C2 = C
Q = Peaking Factor
(Butterworth Q = 0.707)
+
_
V
I
1
R1
R2
f
+
–3dB
2pRC
C2
R
F
R
=
G
1
Q
R
F
2 −
)
(
R
G
V
DD
/2
Figure 31. 2-Pole Low-Pass Sallen-Key Filter
14
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