INA2332: Output difference of INA2332

Fred Yang

Part Number: INA2332

Hi everyone,

I am having some problem with output with the INA2332 based bridge amplifier.
Differential inputs(pin2 of all Header3) are connected together with one bridge circuit using Variable Resisters.
Common mode voltage is 2.5V and differential voltage is 2mV.

I expect the outputs(VoutA and VoutB) show same voltage or slicely different, but they show large difference voltage as one is 2.62V and the other is 0.49V.

If I increase the input differential voltage, the two output voltages increase linearly.
Of course, the values of resisters are checked.

What could be the reason for this difference?

Thanks in advance.

over 5 years ago

0 kai klaas69 over 5 years ago

Guru 140200 points

Hi Fred,

you must still connect the VREF pins to a suited potential.

Kai

0 Zak Kaye over 5 years ago

TI__Mastermind 23050 points

Hi Fred,

As Kai has pointed out, right now your ref pin is floating. You must either ground this node or connect it to your desired reference potential. Just be careful not to violate the input or output swing limitations. To better understand these limitations, you can use our INA Vcm vs. vout tool that can be found here: www.ti.com/.../INA-CMV-CALC

0 Fred Yang over 5 years ago in reply to kai klaas69

Prodigy 40 points

Thanks Kai,
Now I understand that it is remommeded a unity gain amp for each VREF port.
Q1. Is it possible to use a voltage divider using R as a Vref supplier? Is there any consideration?
Q2. Can I use a single unit gain amp for both VREF ports?

0 Fred Yang over 5 years ago in reply to Zak Kaye

Prodigy 40 points

Hi Zak,
The referenced information would be a great help.
Thank you.

0 Zak Kaye over 5 years ago in reply to Fred Yang

TI__Mastermind 23050 points

Hi Fred,

Technically yes, it is possible to use a voltage divider to supply your Vref as long as you have a "stiff" reference, meaning the output is impedance is very low. This is usually impractical because it requires burning lots of current in your reference resistors. The resistance of your divider is also going to impact the non-inverting branch of the internal difference amplifier so you will see some additional gain error as well as a degradation in your CMRR. Using a buffer amplifier is a much better approach and there is no issue using a single buffer to supply both references.

0 Fred Yang over 5 years ago in reply to Zak Kaye

Prodigy 40 points

Hi Zak,
Thanks a lot for your kind and detailed answer.
My question is resolved completly thanks to Zak and Kai.

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INA2332: Output difference of INA2332