OPA348-Q1 Datasheet, PDF (12/30 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
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Feature Description (continued)
7.3.7 EMI Susceptibility and Input Filtering
Op-amps vary with regard to the susceptibility of the device to electromagnetic interference (EMI). If conducted
EMI enters the op-amp, the dc offset observed at the amplifier output may shift from the nominal value while EMI
is present. This shift is a result of signal rectification associated with the internal semiconductor junctions. While
all op-amp pin functions can be affected by EMI, the signal input pins are likely to be the most susceptible. The
OPAx348-Q1 family of devices incorporates an internal input low-pass filter that reduces the amplifiers response
to EMI. Both common-mode and differential mode filtering are provided by this filter. The filter is designed for a
cutoff frequency of approximately 80 MHz (–3 dB), with a roll-off of 20 dB per decade.
Texas Instruments has developed the ability to accurately measure and quantify the immunity of an operational
amplifier over a broad frequency spectrum extending from 10 MHz to 6 GHz. The EMI rejection ratio (EMIRR)
metric allows op-amps to be directly compared by the EMI immunity. Detailed information can also be found in
the application report, EMI Rejection Ratio of Operational Amplifiers (SBOA128), available for download from
www.ti.com.
7.3.8 Rail-to-Rail Output
Designed as a micro-power, low-noise operational amplifier, the OPAx348-Q1 family of devices delivers a robust
output drive capability. A class AB output stage with common-source transistors is used to achieve full rail-to-rail
output swing capability. For resistive loads up to 10 kΩ, the output swings typically to within 5 mV of either supply
rail regardless of the power-supply voltage applied. Different load conditions change the ability of the amplifier to
swing close to the rails; refer to the graph, Output Voltage Swing vs Output Current.
A class AB output stage with common-source transistors is used to achieve rail-to-rail output. This output stage is
capable of driving 5-kΩ loads connected to any potential between V+ and ground. For light resistive loads
(>100 kΩ), the output voltage can typically swing to within 18 mV from supply rail. With moderate resistive loads
(10 kΩ to 50 kΩ), the output voltage can typically swing to within 100 mV of the supply rails while maintaining
high open-loop gain (see Figure 6 in the Typical Characteristics section).
Output (Inverted on Scope)
5V
G = +1V/V, V_S = +5V
0V
20µs/div
Figure 23. Rail-to-Rail I/O
12
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