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OPA140: Input bias current vs temperature

bbrienzo
Prodigy 110 points

Part Number: OPA140

Tool/software:

Is there a plot for the OPA140 of input bias current vs temperature?  The datasheet only shows +/-0.5pA (+/-10pA max) at 25C and +/-3000pA max over the whole temperature range, but I'm assuming it's not a linear ramp.  We have a sensitive application that operates in the 25C-60C range.

  • +1
    TI__Guru 74331 points

    The input bias current, IB, in JFET input op amps like OPA140 is dominated by the leakage current of reverse-biased p-n junction and thus doubles every 10 deg C:  IB(@T) = IB(25C)*2^((T-25C)/10C)

    This means that the typical IB at 60 deg C is: IB_typ (@T=60C) = +/-0.5pA*2^((60C-25C)/10C) = +/-0.5pA*2^3.5 = +/-5.7pA while the maximum IB may be back-calculated from the max of +/-3000pA at 125C to be: IB_max (@T=60C) = +/3000pA/(2^(125C-60C)/10C) = +/-3000pA/(2^6.5) = +/-33pA

  • 0 in reply to Marek Lis
    Prodigy 110 points

    Thanks.  Didn't know if the doubling every 10C was just a rule of thumb or there were other factors.

  • 0 in reply to bbrienzo
    TI__Guru 74331 points

    The leakage current doubling every 10 deg C is a close approximation for any reverse-biased p-n junction.