10

®

INA115

FIGURE 5. Providing an Input Common-Mode Current Path.

FIGURE 4. Optional Trimming of Output Offset Voltage.

47k

Ω

47k

Ω

10k

Ω

Microphone,

Hydrophone

etc.

Thermocouple

Center-tap provides

bias current return.

INA115

INA115

INA115

INA115

V

IN

V

IN

R

G

–

+

10k

Ω

V

O

OPA177

Ref

±10mV

Adjustment Range

100

Ω

100

Ω

100µA

1/2 REF200

100µA

1/2 REF200

V+

V–

FIGURE 3. Switched-Gain Instrumentation Amplifier (improved gain drift).

R

1

R

2

R

3

R

4

R

5

R

6

R

7

GAIN STEPS

(

Ω)(Ω)(Ω)(Ω)(Ω)(Ω)(Ω)

1, 10, 100, 1000V/V

18k

1.8k

180

40

180

1.8k

18k

1, 2, 4, 8V/V

18k

9k

4.5k

9k

4.5k

9k

18k

1, 2, 5, 10V/V

18k

10.8k

3.6k

7.2k

3.6k

10.8k

18k

0, +3, +6, +9dB

18k

12.74k

9.02k

43.7k

9.02k

12.74k

18k

A

0

A

1

Gain

LL

1

HL

LH

H

H

Highest

A

1

A

2

A

3

12

11

10

25k

Ω

25k

Ω

25k

Ω

25k

Ω

13

7

5

4

V

IN

V

IN

INA115

V

O

–

+

Over-Voltage

Protection

25k

Ω

25k

Ω

Over-Voltage

Protection

Feedback

15

14

3

2

8

1

NC

NC

HI-509

–15V

+15V

16

1

2

14

3

15

8

9

4

5

6

7

10

11

12

13

R

1

R

2

R

3

R

4

R

5

R

6

R

7

A

1

A

0

Enable