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INA241A: Do you have the formula for calculating gain error factor for INA 241?

Adam Seubert
Prodigy 10 points
Part Number: INA241A
Other Parts Discussed in Thread: INA240

Tool/software:

I have a design that requires input resistance for EMC protection and I need to be able to calculate the corrected gain. Reading User's Guide Input Resistance Error for Current Sense Amplifiers by TI several methods are offered for calculating this but the INA241 datasheet does not provide the information necessary to calculate it. My DMM shows that RBias is 6.6kΩ, but I need values for Rfb, and Rint (or an abstracted equation).

Please advise!

  • 0
    TI__Mastermind 29870 points

    Hello Adam,

    The INA241 and the INA296 have the same input structure.  An estimate is calculated like the INA240 

    Gain Error Factor  = 3250/ (Rs+3250)

    Gain Error % = 100- (100*Gain Error Factor)

    https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/1261093/ina296b4q---gain-error-factor.

    From simulations  it is closer to: Gain Error Factor  = 2600/ (Rs+2600)

    Regards,

    Javier

  • 0 in reply to Javier Contreras4
    Prodigy 10 points

    According to https://www.ti.com/lit/ug/slya042/slya042.pdf?ts=1736128184347 equation 8 the GEF will be dependent on the series input resistance between Rs and the op amp. The equation you provided doesn't seem to account for this?

    We had to add some series resistance to provide lighting protection and other EMC immunity.

    Thanks,

    Adam

  • 0 in reply to Adam Seubert
    TI__Mastermind 29870 points

    Hello Adam,

    The INA241 has a different input structure.  I ran some simulations to calculate the error for all the variations.  The model of the INA241 has the IB input change vs Vsense in the model along with the IB vs VCM.  I verified it was the same for all the gain options.  The Vsense range is different so the IB at the full scale is not the same for each of the gain variants.   Below I did screen shots of the output voltage for different Rshunts.  This is also not consistent from device to device as you can see the variation if IB due to the specification of IB having a large range of 25µA to 45µA.  This is the initial IB when Vsense = 0.  The slope of IB vs Vsense is not a specification that will be exact from device to device.

    3250 3250
    Rs Resistance External 100 1000
    Gain Error Factor Equation: 3250/(Rs+3250) 0.970149 0.764706
    Gain Error % Equation: 100 - (100*GainErrorFactor) 2.985075 23.52941
    Vout Vout = 4V- 4V(GainError) 3.880597 3.058824

     

     

    Regards,

    Javier