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 INAx126 measures small differential voltage with high common-mode voltage developed between the

noninverting and inverting input. The high input impedance make the INAx126 an excellent choice for a wide

range of applications. The INAx126 can adjust the functionality of the output signals by setting the reference pin,

giving additional flexibility that is practical for multiple configurations.

8.2 Typical Application

Figure 8-1 shows the basic connections required for operation of the INA126. Applications with noisy or high

impedance power supplies may require decoupling capacitors close to the device pins as shown.

The output is referred to the output reference (Ref) pin, which is normally grounded. This connection must be

low-impedance to maintain good common-mode rejection. A resistance of 8 Ω in series with the Ref pin causes

a typical device to degrade to approximately 80-dB CMR.

Figure 8-4 depicts a desired differential signal from a sensor at 1 kHz and 5 mVPP superimposed on top of a

1-VPP, 60-Hz common-mode signal (the 1-kHz signal can not be resolved in this scope trace). The FFT trace in

Figure 8-5 shows the two signals. Figure 8-6 shows the clearly recovered differential signal at the output of the

INA126 operating at a gain of 250. The FFT of Figure 8-7 shows the 60-Hz common-mode is no longer visible.

The dual version INA2126 has feedback-sense connections, SenseA and SenseB, that must be connected to the

respective output pins for proper operation. The sense connection can sense the output voltage directly at the

load for best accuracy.

DESIRED GAIN

RG

NEAREST 1%

(V/V)

(Ω)

RG VALUE

5

NC

NC

10

16k

15.8k

20

5333

5360

50

1779

1780

100

842

845

200

410

412

500

162

162

1000

80.4

80.6

2000

40.1

40.2

5000

16.0

15.8

10000

8.0

7.87

NC: No Connection.

40kΩ

10kΩ

10kΩ

40kΩ

INA126

5

4

2

1

8

3

7

6

R

G

R

G

V

IN

A

2

A

1

–

V

IN

+

V

IN

–

V

IN

+

V+

V–

INA126

0.1µF

0.1µF

V

O

V

O

Ref

Ref

Load

+

–

Also drawn in simplified form:

V

O = (VIN – VIN) G

–

+

G = 5 +

Pin numbers are

for single version

Dual version has

external sense connection.

80kΩ

R

G

Figure 8-1. Basic Connections

www.ti.com

INA126, INA2126

SBOS062C – SEPTEMBER 2000 – REVISED JANUARY 2022

Copyright © 2022 Texas Instruments Incorporated

Submit Document Feedback

13

Product Folder Links: INA126 INA2126