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INA131: IN AMP high gain instability

Jose Barbali1
Prodigy 10 points
Part Number: INA131

Hi. I need to know if there is some drawbacks trying to get an gain of about 1400 with the INA131, maybe instability or noise.

The amplifier is to be used with an input signal of 7 mV (load cell, 10 V, 350 ohms, INA131AP +/-15 V).

 I need to adjust the output to 10 V with a single trimpot (Bourns 3296W 500 ohms) and adjusting the reference with an op amp (+/-2 V).

Thanks in advance.

Jose

  • 0
    TI__Genius 10850 points

    Hi Jose,

    On page 7, section "Setting the Gain" of the datasheet, it describes the ability to set the gain higher than the fixed gain of 100. It is important to note that since the internal resistors are trimmed for precise ratios, the absolute values of the internal resistor will vary from device to device. The absolute accuracy of the internal resistor values is +/-40%. 

    The gain  equation is: G = 100 + (250k/RG), where RG is the external gain resistor and the accuracy of the 250k-ohm internal resistor term is +/-40%.

    So while you can set the gain = 1400, you may run into issues of noise (resistor contribution) and accuracy (+/-40%). 

    -Tamara Alani