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OPA2991: Input Bias Current over Temperature

Part Number: OPA2991
Other Parts Discussed in Thread: OPA2171,

Hello TI,

I am planning on using the OPA2991S in an upcoming project, and one of the specifications that is most critical for the design is input bias current.

While these devices appear to have very low IB, especially on the non-inverting input (which is what I care about), the datasheet does not include a maximum spec, only a typical value.

Is there in fact a tested/guaranteed maximum Ib, or are these devices not guaranteed for that parameter?

We are especially interested in the maximum Ib on the non-inverting pin across the full temperature range (up to 125C).

Thank You,

  • Hi Benjamin,

    if TI would check the maximum input bias current for each OPAmp, they would publish this data in the datasheet for sure. And if they would check the maximum input bias current only sporadically and randomly on a handful of OPAmps, then it would not be helpful for you anyway, because your individual exemplar may exceed the measured values.

    I fear, if the input bias current is critical in your application, the only remedy is to take an OPAmp with specified maximum data in the datasheet,


  • Hey Benjamin, 

    The previous generation of the OPA2991(40V) is the OPA2171(36V) and that has a max specification for Ib in the datasheet of 3.5nA. 
    Here is the datasheet curve: 

    As you can see it is significantly higher than the curve shared from the OPA2991 datasheet, this makes sense as the OPA2991 is for improved performance. 
    As Kai mentioned, if it is critical to your application, I would use an op amp with a max specification in the datasheet. 

    Here is a parametric search filtered by max input bias current: Dual channel, high voltage (>36V), GBW >3MHz, filtered by lowest max Ib 

    All the best,