OPA377_15 Datasheet, PDF (11/27 Pages) Texas Instruments – 5MHz, Low-Noise, Single, Dual, Quad CMOS Operational Amplifiers

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ACTIVE FILTERING
The OPA377 series is well-suited for filter
applications requiring a wide bandwidth, fast slew
rate, low-noise, single-supply operational amplifier.
Figure 25 shows a 50kHz, 2nd-order, low-pass filter.
The components have been selected to provide a
maximally-flat Butterworth response. Beyond the
cutoff frequency, roll-off is –40dB/dec. The
Butterworth response is ideal for applications
requiring predictable gain characteristics such as the
anti-aliasing filter used ahead of an analog-to-digital
converter (ADC).
R₃
5.49kW
C₂
150pF
R₁
5.49kW
R₂
12.4kW
C₁
V_IN
1nF
V+
OPA377
V_OUT
(V+)/2
Figure 25. Second-Order Butterworth 50kHz
Low-Pass Filter
OPA377
OPA2377
OPA4377
SBOS504B – FEBRUARY 2010 – REVISED JANUARY 2011
DRIVING AN ANALOG-TO-DIGITAL
CONVERTER
The low noise and wide gain bandwidth of the
OPA377 family make it an ideal driver for ADCs.
Figure 26 illustrates the OPA377 driving an
ADS8327, 16-bit, 250kSPS converter. The amplifier is
connected as a unity-gain, noninverting buffer.
+5V
C₁
0.1mF
OPA377
(1)
R₁
100W
(1)
C₃
1.2nF
V_IN
+5V
+IN _ADS8327
Low Power
16-Bit
-IN _500kSPS
REF IN
+5V
REF5040
4.096V
C4
100nF
(1) Suggested value; may require adjustment based on specific
application.
(2) Initial calibration recommended.
Figure 26. Driving an ADS8327⁽²⁾
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