7 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.

7.1 Application Information

The OPAx591 are high precision, low power (420μA), high-slew rate (100V/μs), 85V power operational amplifiers

(op amps). These op amps use a proprietary design technique to achieve a very high slewing capability while

consuming minimal power. The low power consumption helps reduce heat generation on the board while the

output swings near the supply rail. The high slew reduces slew related distortion at the output when dealing with

large peak, high frequency signals.

7.2 Typical Applications

7.2.1 High Voltage Instrumentation Amplifier

Current monitoring is a critical function in a wide range of applications. While several current sensing methods

exist, a shunt resistor provides a highly accurate, and robust approach. Designers need to choose between

high-side and low-side current measurements. High-side measurement is often preferred where accuracy and

load protection are critical.

High-side current sense circuits require special consideration of the input and output common-mode limitations

of the amplifier. The biggest challenge in high-side current measurements is making sure that the amplifier can

support and mitigate the errors that are inherent to high common-mode voltage. Designers can attenuate the

common-mode voltage by using a difference amplifier, but significant gain and input impedance trade-offs exist.

High input impedance and large gain is especially critical when measuring small currents. In such cases, an

instrumentation amplifier provides the required input impedance, and gain.

The trade-off is that instrumentation amplifiers have a complex input voltage range that depends on the

common-mode voltage, differential voltage, gain, and reference voltage. The input stage alone is bound by

the input common-mode voltage limitation and the maximum power supply voltage range of the operational

amplifier. Fortunately, the OPAx591 offers a high operating power supply voltage that enables designers to build

a very high common-mode, high impedance, high gain, high common-mode rejection instrumentation amplifier.

This instrumentation amplifier can be used to measure small differential signals in the presence of very high

common-mode voltage.

7.2.1.1 Design Requirements

RG1

100k

RES21A00

RIN1

10k

RG2

100k

RIN2

10k

+

–

OPAx591

V+

VIN+

VOUT

VIN

VREF

V

+

–

OPAx591

V+

V

+

–

OPAx591

V+

V

2k

19k

19k

10k

RL

IL =

100nA

to 1µA

Figure 7-1. OPAx591 Instrumentation Amplifier With RES31A

OPA591, OPA2591

SBOSA47 – FEBRUARY 2026

www.ti.com

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