DESIRED

GAIN

(

W

)

( )

1

NC

NC

2

50.00k

49.9k

5

12.50k

12.4k

10

5.556k

5.62k

20

2.632k

2.61k

50

1.02k

1.02k

100

505.1

511

200

251.3

249

500

100.2

100

1000

50.05

49.9

2000

25.01

24.9

5000

10.00

10

10000

5.001

4.99

NC: No Connection.

A

1

A

2

A

3

6

60k

60k

60k

60k

7

4

3

8

1

2

V

IN

V

IN

R

G

V+

V–

INA118

G = 1 +

50k

R

G

–

+

5

Over-Voltage

Protection

25k

25k

Over-Voltage

Protection

Load

V

+

–

0.1µF

0.1µF

+

–

V

O

R

G

Also drawn in simplified form:

INA118

Ref

V

O

V

IN

–

V

IN

+

Ref

INA118

www.ti.com

SBOS027A – SEPTEMBER 2000 – REVISED JANUARY 2016

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 INA118 measures a small differential voltage with a high common-mode voltage developed between the

noninverting and inverting input. The high common-mode rejection makes the INA118 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 26 shows the basic connections required for operation of the INA118. 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 12

Ω in series with the Ref pin causes a

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

Figure 26 depicts an input signal with a 5-mV, 1-kHz signal with a 1-Vp-p common-mode signal, a condition often

observed in process control systems. Figure 27 depicts the output of the INA118 (gain = 250) depicting the clean

recovered 1-kHz waveform.

Figure 26. Basic Connections

Copyright © 2000–2016, Texas Instruments Incorporated

Submit Documentation Feedback

13

Product Folder Links: INA118