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INA152: Offset voltage sign convention with respect to temperature

Samrat pushpesh
Prodigy 140 points

Part Number: INA152

Hello,

I have one query regarding INA152 input offset voltage .Below table offset drift voltage max  and typical both values are in +/-. 

So the question is at 100 deg cel offset voltage will be +1500uV or -1500uV . what sign do i need to consider at high temperature and at low temperature(-25 deg).

Please resolve this query it will be really helpful.

Thanks & Regards

Samrat Pushpesh

  • 0
    Guru 48395 points

    Hello Samrat

    I can see why it is confusing, the data sheet histograms show a bipolar centered offset distribution while the drifts are single side positive - I am pretty sure you need to interpret that plot as a magnitude plot where the actual distribution is centered bipolar with +/-15uV/C range. So the drift could be either polarity at your 100C. I guess I am also confused that the biggest bar on drift is not zero. Maybe it really is a unipolar drift? 

  • 0 in reply to Michael Steffes
    Prodigy 140 points

    Hello Michael,

    Thanks for your response ,but still i am not sure about it. It is really confusing.

    Is there any method to interpret that histogram? Or do you have any material to understand this kind of histogram of electronics?

    Thanks & Regards 

    Samrat Pushpesh 

     

  • 0
    TI__Guru 71711 points

    Samrat,

    The input voltage offset, Vos, and offset drift in CMOS op amps can be of either polarity (see above +/- sign in front of them).  The typical specifications are set by one-sigma of Normal Gaussian distribution and therefore represent 68% of all units while maximum specs are set by 5 to 6 sigma. Since +/-1500uV is a maximum Vos at 25C, in order to calculate maximum offset at 100C you must add Vos drift component to offset at room temperature.  However, since Vos and drift are NOT correlated, you must add the two compnents are a vextor quantities:  max Vos(@100C) = +/- sq-rt[Vos(25C)^2 + ((100C-25C)*15uV/C)^2] = +/-sq-rt[1500^2 + (75C*15uV/C)^2] = +/-sq-rt[1500^2+1125^2], therefore, max Vos at 100C is = +/-1875uV while at -25C is +/-1677uV.