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INA293: gain deviation

Part Number: INA293
Other Parts Discussed in Thread: INA190


we need a programmable current source 1..12mA (2..24V), 50kHz for IEPE sensors
with over voltage protection up to ± 100V

we built 3 prototypes with this circuit.
The gain is different for all 3 prototypes (between 17 and 22)
In the "Application Information" the shunt resistor is in the mΩ range. Could this be the reason for the gain deviation?

Thanks for your support!

Best regards,


  • Alen,

    There are two issues in the circuit and they will both be because of the INA293 Input bias current.  Normally these current sense amplifiers are used for higher current applications.  It seems you need the bandwidth but if high bandwidth is not required we do have an INA190 which is lower input bias current but this also has limited input VCM max of 26V which is right at the limit of your input.

    One improvement to the circuit can be done by changing your input resistors to 0 Ω instead of 10 Ω.  When I have attached a Tina Simulation 3782.INA293_in_current_source.TSC showing the difference of Vshunt (voltage across Vshunt) vs V_INA293 (Voltage seen at INA293 input).  The difference is due to the input bias current.  Please note that even with this improvement that you will still have input bias current and will still cause and error but will be reduce much more than what you are seeing.

    Input Votlage Offset will be a much lower error source in your circuit.INA293_in_current_source.TSC

    In the INA293 datasheet you can observe the Input Bias current in different conditions in the typical opeating curve and the INA293 simulation model this can also be observed.  Please see INA293 tina model.