INA106

6

SBOS152A

www.ti.com

To make a high performance high gain instrumentation amplifier, the INA106

can be combined with state-of-the-art op amps. For low source impedance

applications, OPA37s will give the best noise, offset, and temperature drift. At

source impedances above about 10k

Ω, the bias current noise of the OPA37

reacting with input impedance degrades noise. For these applications, use an

OPA111 or a dual OPA2111 FET input op amp for lower noise. For an

electrometer grade IA, use the OPA128—see table below.

Using the INA106 for the difference amplifier also extends the input common-

mode range of the instrumentation amplifier to

±10V. A conventional IA with

a unity-gain difference amplifier has an input common-mode range limited to

±5V for an output swing of ±10V. This is because a unity-gain difference amp

needs

±5V at the input for 10V at the output, allowing only 5V additional for

common-mode.

GAIN

CMRR

NOISE AT 1kHz

(

Ω)(kΩ) (V/V)

(dB)

(nV/

OPA37A

50.5

2.5

1000

128

40000

4

OPA111B

202

10

1000

110

1

10

OPA128LM

202

10

1000

118

0.075

38

FIGURE 8. Precision G = 11 Buffer.

FIGURE 3. Difference Amplifier with Gain and CMR Adjust.

FIGURE 4. Precision G = –10 Inverting Amplifier.

This circuit follows an 11/1 divider with a gain of 11 for an overall gain of unity.

With an 11/1 divider, the input signal can exceed 100V without damage.

FIGURE 5. Voltage Follower with Input Protection.

FIGURE 6. Precision Instrumentation Amplifier.

FIGURE 7. Precision Summing Amplifier.

10

Ω

10

Ω

10k

Ω

100k

Ω

10k

Ω

100k

Ω

200

Ω

200

Ω

V

1

V

2

2

3

5

1

6

E

0

Gain

Adjust

CMR

Adjust

INA106

To eliminate adjustment interactions,

first adjust gain with V

25

6

INA106

V

O

3

R

3

10k

Ω

V

V

IN

R

1

10k

Ω

R

4

100k

Ω

1

R

2

100k

Ω

±100V

Safe Input

E

1

–In

2

3

5

1

6

INA106

E

A

2

A

1

E

2

+In

R

1

R

2

E

0

Output

R

2

25

6

INA106

V

0

V

1

R

1

10k

Ω

R

4

100k

Ω

1

R

2

100k

Ω

R

3

10k

Ω

3

V

3

V

5

6

INA106

V

1

2

V

IN

3

V

O

Gain Error =

0.01% maximum

100k

Ω

10k

Ω

100k

Ω

10k

Ω

V

2

25

6

INA106

V

O

3

V

1

Gain Error = 0.01% maximum

Nonlinearity = 0.001% maximum

Gain Drift = 2.ppm/°C

10k

Ω

100k

Ω

10k

Ω

100k

Ω