R

G

R

F

R

1

C

1

V

IN

V

OUT

= 1 +

V

V

OUT

IN

R

R

F

G

1

1 + sR C

1

1

(

((

(

1

2pR C

1

1

f

=

-

3 dB

21

OPA314-Q1, OPA2314-Q1, OPA4314-Q1

www.ti.com

SLOS896B – DECEMBER 2014 – REVISED JANUARY 2017

Product Folder Links: OPA314-Q1 OPA2314-Q1 OPA4314-Q1

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Copyright © 2014–2017, Texas Instruments Incorporated

8 Application and Implementation

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 OPAx314-Q1 family 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

OPAx314-Q1 family 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 OPAx314-Q1 family 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 shown in Figure 34.

Figure 34. Single-Pole Low-Pass Filter

If additional attenuation is needed, a multiple pole filter is required. The Sallen-Key filter can be used for this

task, as shown in Figure 35. For best results, the amplifier must have a bandwidth that is eight to ten times the

filter frequency bandwidth. Failure to follow this guideline can result in phase shift of the amplifier.