INA129 - single supply at +5V and GND?

Peter Wu1

Other Parts Discussed in Thread: INA129, INA326, INA188, INA333, TINA-TIPart Number: INA129

Question type: Development and troubleshooting

Support topic: /Product/Development and troubleshooting/Help with board layout or design considerations/

Description of the problem: Am I able to use the part, INA129, powered with a single supply at +5V and GND?

over 7 years ago

0 Pete%20Semig over 7 years ago

TI__Mastermind 25795 points

Hello Peter,

You can use the INA129 with a single 5V supply, but please understand that the linear operating region (Vcm vs. Vout) will be very limited due to the internal amplifiers' common-mode and output swing limitations. I recommend reading the articles in the following FAQ and downloading the Vcm vs. Vout calculator.

Vcm vs. Vout FAQ:

https://e2e.ti.com/support/amplifiers/precision_amplifiers/w/design_notes/3373.understanding-instrumentation-amplifier-vcm-vs-vout-plots

INA Common-mode Calculator download:

http://www.ti.com/tool/ina-cmv-calc

An alternate part that you may consider is the INA326. The INA326 has a unique topology that enables RRI/O operation.

0 Peter Wu1 over 7 years ago in reply to Pete%20Semig

Prodigy 50 points

I used the Vcm calculator and it looks like at +5Vin and gain of 1 V/V, Vout and Vin will only be linear from 1.87V max to 0.8V min with a common mode voltage of 2.66V. I'm a little confused about why the CM voltage bar only lets me go from 2.13V to 3.2V. Why can't I set the CM to 0V?

I think INA188 might be a better option. The datasheet specifically says it can operate with a single supply and goes rail to rail.

0 Pete%20Semig over 7 years ago in reply to Peter Wu1

TI__Mastermind 25795 points

Hello Peter,

You can set the Vcm to 0V, but you'll be violating the linear operating region of the device. Please read the articles in the FAQ...especially the first 3 which discuss 3 op amp instrumentation amplifiers. The INA188 is also a 3 op amp instrumentation amplifier so it's linear operating region will also look like a triangle when operated single supply with Vref=0. The maximum output swing will be from 220mV to ~3.3V when Vcm=~1.86V.

Hope this helps!

0 Peter Wu1 over 7 years ago in reply to Pete%20Semig

Prodigy 50 points

The INA common-mode calculator does not have INA326 part loaded. Is it because it's RR I/O and therefore doesn't have a plot?

I did a simulation in Tina with the INA326 in the circuit I plan to use and it behaves like I expected. But I also did the simulation using the INA333 instead, and it works the same. Vcm is 0V. Vdiff is less than 1V. V+ is +5V, V- is GND, and Gain = 1, Ref = 0.

0 Pete%20Semig over 7 years ago in reply to Peter Wu1

TI__Mastermind 25795 points

Hello Peter,

Yes, the INA326 has a special topology that allows for RRI/O. Therefore it does not conform to the same limitations as traditional instrumentation amplifiers. Please note that TINA-TI models do not necessarily model Vcm vs. Vout limitations...that is why we created the common-mode calculator.

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INA129 - single supply at +5V and GND?