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INA126 non-linear operation

Other Parts Discussed in Thread: INA126

Hi there,

Currently i'm trying to design a whetstone bridge circuit using load cell. The instrumentation amplifier which im using is the IN126 , and I have a 0-12V single powered power supply breakout.

The input to the amplifier is from the regulated power supply. The gain of the amplifier is 13 (Rg is chosen as 10K). The input what im giving is less than 0.5V. In my case ive tried giving 0.4V and 0.22V as the input. I have a pair of INA126, so ive compared the output of the two but it seems to be different for each...

For one of the INA126,

for input  = 0.4V, the output what ive got is 6.65V. But the expected output is 5.2V.

for input = 0.22V, the output what ive got is 5.65V. But the expected output is 2.86V

For the another INA126, ive given the same inputs

for input  = 0.4V, the output what ive got is 5.1V. But the expected output is 5.2V.

for input = 0.22V, the output what ive got is 5.8V. But the expected output is 2.86V

I have attached a schematic showing the setup I have. Any help would be much appreciated!

  • Hi Gurudatta,

    It looks like you are operating the amplifier outside of its Input Common Mode Voltage Range. A couple of questions:

    1. At what supply voltage did you see these results?
    2. What is your common mode voltage at your inputs?

    Best Regards,
    Mihir Gupta
    Field Applications Engineer
    Texas Instruments