OPA322-Q1 Datasheet, PDF (16/26 Pages) Texas Instruments – CMOS Operational Amplifier With Shutdown

OPA322-Q1, OPA322S-Q1
OPA2322-Q1, OPA2322S-Q1
OPA4322-Q1, OPA4322S-Q1
SLOS856A – JUNE 2013 – REVISED JUNE 2013
www.ti.com
Standard PCB-assembly techniques allow for easy mounting of the DFN package. See the application reports,
QFN/SON PCB Attachment (SLUA271) and Quad Flatpack No-Lead Logic Packages (SCBA017), both available
for download at www.ti.com. Connect the exposed leadframe die pad on the bottom of the DFN package to
the most-negative potential (V–). The dimension of the exposed thermal die pad is 2 mm ×
1,2 mm and is centered.
APPLICATION EXAMPLES
ACTIVE FILTER
The OPA322-Q1 is well-suited for active filter applications that require a wide-bandwidth, fast-slew-rate, low-
noise, single-supply operational amplifier. Figure 37 shows a 500-kHz, second-order, low-pass filter using the
multiple-feedback (MFB) topology. The component selection provides a maximally-flat Butterworth response.
Beyond the cutoff frequency, rolloff is –40 dB/decade. The Butterworth response is ideal for applications that
require predictable gain characteristics, such as the anti-aliasing filter used in front of an ADC.
One point to observe when considering the MFB filter is its inverted output, relative to the input. If this inversion
is not required, or not desired, a one can achieve a noninverting output through one of these options:
1. Adding an inverting amplifier
2. Adding an additional second-order MFB stage
3. Using a noninverting filter topology, such as the Sallen-Key (shown in Figure 38).
One can quickly accomplish MFB and Sallen-Key, low-pass and high-pass filter synthesis using TI’s FilterPro™
program. This software is available as a free download at www.ti.com.
R₃
549 W
C₂
150 pF
R₁
R₂
549 W 1.24 kW
V_IN
C₁
1 nF
V+
OPA322-Q1
V-
V_OUT
Figure 37. Second-Order Butterworth 500-kHz Low-Pass Filter
V_IN = 1 V_RMS
1.8 kW
220 pF
V+
19.5 kW 150 kW
3.3 nF
47 pF ^OPA322-Q1
V_OUT
V-
Figure 38. OPA322-Q1 Configured as a Three-Pole, 20-kHz, Sallen-Key Filter
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