®

7

INA116

APPLICATIONS INFORMATION

Figure 1 shows the connections required for basic operation

of the INA116. Applications with noisy or high impedance

power supplies may require decoupling capacitors close to

the supply 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 resis-

tance of 30

Ω in series with this connection will cause a

typical device to degrade to approximately 72dB CMR at

G = 1.

SETTING THE GAIN

Gain of the INA116 is set by connecting a single external

Commonly used gains and resistor values are shown in

Figure 1.

The 50k

Ω term in equation 1 is the sum of the two feedback

resistors of A

laser trimmed to accurate absolute values. The accuracy and

temperature coefficient of these resistors are included in the

gain accuracy and drift specifications of the INA116.

inferred from the gain equation (1). Low resistor values

required for high gain make wiring resistance important.

Sockets add to the wiring resistance that will contribute

additional gain error in gains of approximately 100 or

greater.

OFFSET TRIMMING

The INA116 is laser trimmed for low offset voltage and

offset voltage drift; most applications require no external

offset adjustment. Figure 2 shows an optional circuit for

trimming the output offset voltage. A voltage applied to the

Ref terminal is summed at the output. Op amp A

a low source impedance for the Ref terminal, assuring good

common-mode rejection.

G

= 1 +

50k

Ω

R

G

(1)

FIGURE 1. Basic Connections.

INA116

R

G

Also drawn in simplified form:

V

O

Ref

V

IN

–

V

IN

+

A

1

A

2

A

3

R

4

60k

Ω

R

3

60k

Ω

R

2

60k

Ω

R

1

60k

Ω

V

IN

V

IN

R

G

V–

INA116

V

O

Ref

G = 1 +

50k

Ω

R

G

–

+

R

FB

25k

Ω

R

FB

25k

Ω

+1

+1

Over-Voltage

Protection

Over-Voltage

Protection

4

3

2

1

16

5

6

7

8

11

9

13

Input Guards

See Text.

0.1µF

V+

0.1µF

DESIRED

GAIN

1

2

5

10

20

50

100

200

500

1000

2000

5000

10000

NC: No Connection.

R

G

(

Ω)

NC

50.00k

12.50k

5.556k

2.632k

1.02k

505.1

251.3

100.2

50.05

25.01

10.00

5.001

NEAREST 1% R

G

(

Ω)

NC

49.9k

12.4k

5.62k

2.61k

1.02k

511

249

100

49.9

24.9

10

4.99