OPA348-Q1 Datasheet, PDF (14/30 Pages) Texas Instruments – OPAx348-Q1 1-MHz 45-μA CMOS Rail-to-Rail Operational Amplifier

OPA348-Q1, OPA2348-Q1, OPA4348-Q1
SBOS465B – JANUARY 2009 – REVISED DECEMBER 2014
8 Application and Implementation
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NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
The OPAx348-Q1 operational amplifiers (op-amps) are unity-gain stable and suitable for a wide range of general-
purpose applications.
The OPAx348-Q1 device features wide bandwidth and unity-gain stability with rail-to-rail input and output for
increased dynamic range. Figure 23 shows the input and output waveforms for the OPAx348-Q1 device in unity-
gain configuration. Operation is from a single 5-V supply with a 100-kΩ load connected to V_S / 2. The input is a
5-V_PP sinusoid. Output voltage is approximately 4.98 V_PP.
The power-supply pins should be bypassed with 0.01-µF ceramic capacitors.
8.1.1 Driving Analog-to-Digital Converters (ADCs)
The OPAx348-Q1 op-amps are optimized for driving medium-speed sampling ADCs. The OPAx348-Q1 op amps
buffer the ADC input capacitance and resulting charge injection while providing signal gain.
Figure 26 shows the OPA2348 in a basic noninverting configuration driving the ADS7822 device. The ADS7822
device is a 12-bit, micropower sampling converter in the MSOP-8 package. When used with the low-power
miniature packages of the OPAx348-Q1 family of devices, the combination is ideal for space-limited, low-power
applications. In this configuration, an RC network at the ADC input can be used to provide for antialiasing filtering
and charge injection current.
5V
0.1 µF
0.1 µF
VIN
1/2
OPA2348-Q1
VIN = 0 V to 5 V for
0-V to 5-V output.
500 Ω
3300 pF
8 V+
+IN
2
–IN
3
ADS7822
12-Bit A/D
GND 4
1 VREF
7
DCLOCK
DOUT ⁶
5
CS/SHDN
Serial
Interface
RC network filters high-frequency noise.
NOTE: A/D Input = 0 to V_REF
Figure 26. Noninverting Configuration Driving ADS7822
The OPAx348-Q1 family of devices can also be used in noninverting configuration driving the ADS7822 device in
limited low-power applications. In this configuration, an RC network at the ADC input can be used to provide for
antialiasing filtering and charge injection current. See Figure 26 for the OPAx348-Q1 driving an ADS7822 device
in a speech bandpass filtered data acquisition system. This small low-cost solution provides the necessary
amplification and signal conditioning to interface directly with an electret microphone. This circuit operates with
V_S = 2.7 V to 5 V with less than 250-µA typical quiescent current.
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