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OPA333: How to calculate input offset voltage

Part Number: OPA333

Hi,

I would like to ask you a basic question about input offset voltage.

According to the datasheet, Vos = 10uV(Max) @ 25℃ and offset drift is 0.05uV/℃.

In case of Vos is 10uV @25℃ now, when the temperature is going to 125℃, the Vos is going to 15uV (10+0.05x100=15).

That is to say, Vos(Max) is 15uV @-40 to 125℃.

Is this correct? 

Thank you for your support.

Best Regards,

  • Suzuki-san,

    For the most part, you are correct in your calculation of the worst case Vos over entire temperature range.  However, I would just caution you that even though datasheet specifies Vos and drift as a positive number, in fact both of them are as likely to be positive as they are to be negative (btw, offset voltage drift distribution below shows an absolute value).

    Also, since the offset voltage and drift are NOT correlated to one another, instead of adding them linearly as you did, you should add them as sum of squares: [10^2+(100*0.05)^2]^0.5=+/-11.2uV;  

  • Hi Marek-san,

    Thank you for your answer !
    I understood.
    I forgot that the offset data is "standard deviation"...

    Regards,