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INA2141 with gain other than 10 or 100

Phillip Karls
Prodigy 250 points
Other Parts Discussed in Thread: INA2141, INA141

I'm attempting to use an INA2141 with a gain of approximately 14.4V/V using the following equation:

G = 1+ (50000/(504+R||5050))

Everything seems to be working fine but I'm seeing a significant gain error across all channels (> +/-1%).

I'm using a 0.1% resistor for the setting the gain.  The maximum gain error for the INA2141 is less than +/-0.075%.

When I actually measure the resistance across the gain resistors I do see alot of variance, telling me the error is occurring in the INA stage. I would have thought the internal resistances of the INA2141 would be tightly controlled due to its small gain error spec.

Can anyone explain this?

When they actually trim the internal gain resisters of the INA2141, are they actually trimming the feedback resistors (25k) as well?

Thanks in advance for your help.

Phillip

  • 0
    TI__Mastermind 25795 points
    Hello Phillip,

    There is a +/-25% variation in the absolute values of the internal resistors. Using an external resistor to set the gain can therefore yield significant gain error. There is a discussion of this on page 8 of the INA141 data sheet.

    The reason why the INA141 has excellent gain error without an external resistor is because the internal resistors are trimmed ratiometrically.