RG

Also drawn in simplified form:

Ref

VO

VIN

VIN

+

49.4k

R

G

NC: No Connection

A

1

A

2

A

3

6

7

4

3

8

1

2

V

IN

VIN

RG

V+

+

5

Over Voltage

Protection

Over Voltage

Protection

Load

+

O

V

Ref

0.1 F

µ

0.1 F

V-

µ

24.7k

Ω

24.74k

Ω

40k

Ω

40k

Ω

40k

Ω

40k

Ω

V

O = G

(V

- V )

·

IN

IN

-

+

-

-

-

G = 1 +

DESIRED

GAIN (V/V)

R

( )

G

NEAREST

1% R ( )

G

1

2

5

10

20

50

100

200

500

1000

2000

5000

10000

NC

49.4K

12.35K

5489

2600

1008

499

248

99

49.5

24.7

9.88

4.94

NC

49.9K

12.4K

5.49K

2.61K

1K

499

249

100

49.9

24.9

9.76

4.87

INA129-EP

www.ti.com

SBOS508A – DECEMBER 2009 – REVISED DECEMBER 2015

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 INA129-EP device measures small differential voltage with high common-mode voltage developed between

the non-inverting and inverting input. The high-input voltage protection circuit in conjunction with high input

impedance make the INA129-EP suitable for a wide range of applications. The ability to set the reference pin to

adjust the functionality of the output signal offers additional flexibility that is practical for multiple configurations.

8.2 Typical Application

Figure 16 shows the basic connections required for operation of the INA129-EP. 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) terminal which is normally grounded. This must be a low-

impedance connection to assure good common-mode rejection. A resistance of 8

Ω in series with the Ref pin will

cause a typical device to degrade to approximately 80 dB CMR (G = 1).

Figure 16. Basic Connections

8.2.1 Design Requirements

The device can be configured to monitor the input differential voltage when the gain of the input signal is set by

the external resistor RG. The output signal references to the REF pin. The most common application is where the

output is referenced to ground when no input signal is present by connecting the REF pin to ground, as

Figure 16 shows. When the input signal increases, the output voltage at the OUT pin increases, too.

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