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INA818: Differential Input Voltage

Chikako Nakayama
Prodigy 10 points
Part Number: INA818

The datasheet of INA818 discribes two equations, G=1 + 50k/Rg and Vo=G*(Vin- - Vin+).

When I select Rg=239, G=1 + 50k/239 = about 26 and Vo=26*(Vin- - Vin+).

Then, when I measured Vo in Vin-=-0.3 and Vin+=4.7 (Vdiff=-5.0 V), this actual value is almost same as the expected value (-14.85 V caluclated by Analog Engineer's Caluclator).

It seems that INA818 works correctly in this condition (very high Vdiff), but some amplifier has a range of defferential input voltage.

Does INA818 have absolute maximum ratings of defferential input voltage?

  • 0
    TI__Mastermind 18425 points

    Hello Chikako, 

    The engineer calculator will provide a max output and a min output that is able to be achieved under the conditions you put into the calculator and these values could be divided by the gain in order to determine the max input differential that can be applied without clipping. Regarding the max input voltage the device can sustain, this is +/-60V. 

    I hope this explanation helps. Let me know if you have any further questions. 

    Best Regards, 

    Chris Featherstone

  • 0 in reply to Chris Featherstone
    Prodigy 10 points

    Hello Chris, thank you for your answer.

    Just to confirm, INA818 does not have absolute maximum ratings of defferential input voltage, right?

    For example, even when I set Vin-=-60V and Vin+=60V, INA818 do not fail?

    As a side note, apart from absolute maximum ratings, does this amplifier have the range of input or output valtages that are guaranteed correct working?

  • 0 in reply to Chikako Nakayama
    TI__Mastermind 18425 points

    Hello Chikako, 

    The abs max differential voltage is +/-60V meaning that you can have -60V on one input pin and +60V on the other input pin. The device can sustain this much differential voltage. 

    The engineer calculator provides the linear operating conditions for the input voltage. If you provide the following information I can show an example. 

    Can you provide the following conditions for your application circuit?:

    • Supply Voltage
    • Vcm voltage 
    • Reference voltage 
    • Gain

    Best Regards, 

    Chris Featherstone