OPA314_15 Datasheet, PDF (20/45 Pages) Texas Instruments – OPAx314 3-MHz, Low-Power, Low-Noise, RRIO, 1.8-V CMOS Operational Amplifier

OPA314, OPA2314, OPA4314
SBOS563G – MAY 2011 – REVISED JUNE 2015
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 OPA2314 device is a low-power, rail-to-rail input and output operational amplifier specifically designed for
portable applications. The device operates from 1.8 V to 5.5 V, is unity-gain stable, and suitable for a wide range
of general-purpose applications. The class AB output stage is capable of driving ≤ 10-kΩ loads connected to any
point between V+ and ground. The input common-mode voltage range includes both rails, and allows the
OPA2314 device to be used in virtually any single-supply application. Rail-to-rail input and output swing
significantly increases dynamic range, especially in low-supply applications, and makes the device ideal for
driving sampling analog-to-digital converters (ADCs).
The OPA2314 device features a 3-MHz bandwidth and 1.5-V/μs slew rate with only 150-μA supply current per
channel, providing good AC performance at very low power consumption. DC applications are also well served
with a very-low input noise voltage of 14 nV/√Hz at 1 kHz, low-input bias current (0.2 pA), and an input offset
voltage of 0.5 mV (typical).
8.1.1 General Configurations
When receiving low-level signals, limiting the bandwidth of the incoming signals into the system is often required.
The simplest way to establish this limited bandwidth is to place an RC filter at the noninverting terminal of the
amplifier, as Figure 36 shows.
R_G
R_F
R₁
V_IN
V_OUT
C₁
f_{-3 dB} =
1
2pR₁C₁
( ( ^VOUT
V_IN
=
1
+
R_F
R_G
1
1 + sR₁C₁
Figure 36. Single-Pole Low-Pass Filter
If even more attenuation is needed, a multiple pole filter is required. The Sallen-Key filter can be used for this
task, as Figure 37 shows. For best results, the amplifier should have a bandwidth that is eight to 10 times the
filter frequency bandwidth. Failure to follow this guideline can result in phase shift of the amplifier.
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