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Gain Error and Gain Nonlinearity Measurements of TI's Instrumentation Amplifiers

tom sutton
Prodigy 20 points
Other Parts Discussed in Thread: INA333

How is the gain error and gain nonlinearity measured on TI's instrumentation amplifiers (e.g. INA333)? 1) When finding the gain error is the gain error calculated by comparing the worst case measured gain versus an ideal gain, or is it calculated by comparing the worst case measured gain versus a best fit line of the gain over the swept inputs, or is there another method used? 2) What step size is used when sweeping the differential input when measuring gain error and gain nonlinearity? 3) How is the gain nonlinearity measured and calculated? Thanks.

  • 0
    TI__Prodigy 10 points

    The gain error is calculated by comparing worst case gain to ideal gain while gain non-linearity is calculated using best fit line after sweeping the input across the input range.

  • 0 in reply to Manu Suryavansh
    Prodigy 20 points

    Thanks Manu.

    When the input is swept for finding the gain error and gain nonlinearity on an instrumentation amp (e.g. INA333), is there a certain number of steps the input is swept. E.g. At gain of 1000 and a supply voltage of 3v. The input can only be swept from ~ -1.5mv to +1.5mv, so would the number of steps be 30 with each step size be about 0.1mv per step or would it be something different?

  • 0 in reply to tom sutton
    TI__Genius 12631 points

    Tom,

         When we characterize the part prior to release we run high resolution sweeps across multiple devices/lots to understand the behavior of the INA. The sweeps will be run across temperatures, gain settings and power supplies. Based on this characterization data we get a good idea of the behavior of the part and use this information to design our test solution. If we find the particular product gives the same linearity results with a 10 point slope as it does with a 50 point, and the linearity at 100 can be determined from the gains at 1 & 10, that is what we test to. Hope this helps.

    Regards,

    Samir