OPA186DBVT datasheet(23/48 Pages) TI

23 / 48 page

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, as well as validating and testing their design

implementation to confirm system functionality.

8.1 Application Information

The OPAx186 operational amplifier combines precision offset and drift with excellent overall performance,

making the device an excellent choice for many precision applications. The precision offset drift of only

0.01 µV/°C provides stability over the entire temperature range. In addition, the device pairs excellent CMRR,

PSRR, and AOL dc performance with outstanding low-noise operation. As with all amplifiers, applications with

noisy or high-impedance power supplies require decoupling capacitors close to the device pins. In most cases,

0.1

‑µF capacitors are adequate.

8.1.1 Basic Noise Calculations

Low-noise circuit design requires careful analysis of all noise sources. In many cases, external noise sources

can dominate; consider the effect of source resistance on overall op-amp noise performance. Total noise of the

circuit is the root-sum-square combination of all noise components.

The resistive portion of the source impedance produces thermal noise proportional to the square root of the

resistance. The source impedance is usually fixed; consequently, select op amp and the feedback resistors that

minimize the respective contributions to the total noise.

Figure 8-1 shows both noninverting (A) and inverting (B) op-amp circuit configurations with gain. In circuit

configurations with gain, the feedback network resistors also contribute noise. In general, the current noise of the

op amp reacts with the feedback resistors to create additional noise components. However, the extremely low

current noise of the OPAx186 means that the current noise contribution can be ignored.

The feedback resistor values can generally be chosen to make these noise sources negligible. Low impedance

feedback resistors load the output of the amplifier. The equations for total noise are shown for both

configurations.

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OPA186, OPA2186, OPA4186

SBOS968B – JUNE 2022 – REVISED DECEMBER 2022

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OPA186DBVT датащи(PDF) 23 Page - Texas Instruments