OPA211_15 Datasheet, PDF (26/45 Pages) Texas Instruments – Low Power, Precision Operational Amplifier

OPA211, OPA2211
SBOS377H – OCTOBER 2006 – REVISED NOVEMBER 2015
9.2 Typical Application
Input
R4
2.94 k
R1
590
R3
499
C2
39 nF
C5
1 nF
±
+
OPAx211
Output
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Figure 49. OPA211 Simplified Schematic
9.2.1 Design Requirements
Lowpass filters are commonly employed in signal processing applications to reduce noise and prevent aliasing.
The OPAx211 are ideally suited to construct high-speed, high-precision active filters. Figure 49 shows a second
order lowpass filter commonly encountered in signal processing applications.
Use the following parameters for this design example:
• Gain = 5 V/V (inverting gain)
• Lowpass cutoff frequency = 25 kHz
• Second order Chebyshev filter response with 3-dB gain peaking in the passband
9.2.2 Detailed Design Procedure
The infinite-gain multiple-feedback circuit for a low-pass network function is shown in . Use Equation 1 to
calculate the voltage transfer function.
Output _s
Input
s²
1 R₁R₃C₂C₅
s C₂ 1 R₁ 1 R₃ 1 R₄ 1 R₃R₄C₂C₅
(1)
This circuit produces a signal inversion. For this circuit, the gain at DC and the lowpass cutoff frequency are
calculated by Equation 2:
Gain ^R4
R₁
f_C
1
2S
1 R₃R₄C₂C₅
(2)
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and easy-to-use active filter design program. The WEBENCH Filter Designer lets you create optimized filter
designs using a selection of TI operational amplifiers and passive components from TI's vendor partners.
Available as a web based tool from the WEBENCH® Design Center, WEBENCH® Filter Designer allows you to
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