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| OPA313_15 Datasheet, PDF (19/38 Pages) Texas Instruments – 1-MHz, Micro-Power, Low-Noise, RRIO,1.8-V CMOS OPERATIONAL AMPLIFIER Precision Value Line Series | |||
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OPA313
OPA2313
OPA4313
SBOS649C â SEPTEMBER 2012 â REVISED MARCH 2013
APPLICATION EXAMPLES
GENERAL CONFIGURATIONS
When receiving low-level signals, limiting the bandwidth of the incoming signals into the system is often required.
The simplest way to establish this limited bandwidth is to place an RC filter at the noninverting terminal of the
amplifier, as Figure 37 shows.
RG
RF
R1
VIN
VOUT
C1
f-3 dB =
1
2pR1C1
( ( VOUT
VIN
=
1
+
RF
RG
1
1 + sR1C1
Figure 37. 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, as Figure 38 shows. For best results, the amplifier should have a bandwidth that is eight to 10 times the
filter frequency bandwidth. Failure to follow this guideline can result in phase shift of the amplifier.
C1
R1
R2
VIN
C2
RF
RG
VOUT
R1 = R2 = R
C1 = C2 = C
Q = Peaking factor
(Butterworth Q = 0.707)
f-3 dB =
1
2pRC
RF
( RG =
2-
1
Q
Figure 38. Two-Pole Low-Pass Sallen-Key Filter
Copyright © 2012â2013, Texas Instruments Incorporated
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Product Folder Links: OPA313 OPA2313 OPA4313
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