9 Power Supply Recommendations

9.1 Low-Voltage Operation

The INAx126 can be operated on power supplies as low as ±1.35 V. Performance remains excellent with power

supplies ranging from ±1.35 V to ±18 V. Most parameters vary only slightly throughout this supply voltage

range (see Section 6.7). Operation at low supply voltage requires careful attention to make sure that the

common-mode voltage remains within the linear range (see Figure 6-5 and Figure 6-6).

The INAx126 operates from a single power supply with careful attention to input common-mode range, output

voltage swing of both op amps, and the voltage applied to the Ref pin. Figure 9-1 shows a bridge amplifier circuit

operated from a single 5-V power supply. The bridge provides an input common-mode voltage near 2.5 V, with a

relatively small differential voltage.

40kΩ

10kΩ

10kΩ

40kΩ

INA126

5

1.2V

4

4

6 8

2

1

8

3

7

6

R

G

R

1

1kΩ

C

1

0.47µF

R

2

1kΩ

+5V

R

1, C1, R2:

340Hz LP

Bridge

Sensor

2.5V –∆V

2.5V + ∆V

REF1004C-1.2

33µA

2

3

1

+IN

–IN

V

REF

D

ADS7817

12-Bit

A/D

C

S

Ck

6

Serial

Data

Chip

Select

INA126 and ADS7817

are available in fine-pitch

MSOP-8 package

Dual version has external

sense connection. Pin numbers

shown are for single version.

Clock

5

7

4

8

A

2

A

1

The ADS7817’s VREF input current is proportional to conversion rate. A

conversion rate of 10kS/s or slower assures enough current to turn on the

reference diode. Converter input range is ±1.2V. Output swing limitation of

INA126 limits the A/D converter to somewhat greater than 11 bits of range.

A similar instrumentation amplifier, INA125, provides

an internal reference voltage for sensor excitation

and/or A/D converter reference.

Figure 9-1. Bridge Signal Acquisition, Single 5-V Supply

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INA126, INA2126

SBOS062C – SEPTEMBER 2000 – REVISED JANUARY 2022

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