OPA202IDBVT datasheet(26/47 Pages) TI1

26 / 47 page

OPA202, OPA2202, OPA4202

SBOS812E – OCTOBER 2017 – REVISED FEBRUARY 2020

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Product Folder Links: OPA202 OPA2202 OPA4202

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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 OPA202, OPA2202, and OPA4202 (OPAx202) are unity-gain stable operational amplifiers with low noise,

low input bias current, and low input offset voltage. Applications with noisy or high-impedance power supplies

require decoupling capacitors placed close to the device pins. In most cases, 0.1-µF capacitors are adequate.

Designers can use the low output impedance and heavy capacitive load drive abilities to interface to modern,

fast-acquisition, precision analog-to-digital converters (ADCs) and buffer precision voltage references and drive

power supply decoupling capacitors.

8.1.1 Basic Noise Calculations

Low-noise circuit design requires careful analysis of all noise sources. External noise sources dominates in many

cases; 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. Figure 42 shows this function. The source impedance is usually fixed; consequently, select the op

amp and the feedback resistors to minimize the respective contributions to the total noise.

Figure 46 shows noninverting (A) and inverting (B) op amp circuit configurations with gain. In circuit

configurations with gain, the feedback network resistors contribute noise. Typically, 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 OPAx202 means that the current noise contribution is neglected.

The feedback resistor values are typically selected 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.

OPA202IDBVT Datasheet(PDF) 26 Page - Texas Instruments