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TLV272: Bias Current vs Temperature - details needed

Jeffrey Casey
Prodigy 60 points
Part Number: TLV272

My client is having a critical problem with an existing product.    We need to know the slope of bias current vs temperature in the range of the application for the TLV272IDR op-amp.   The plots on the spec sheet are scaled for extreme temperatures, and are useless for us.

We have this op-amp configured as a unity gain buffer.  The nominal temperature is in the 35-45C range.  The nominal signal is 1-4V DC.  The supply rails are 0V, +5V.

Any help appreciated!

Jeff Casey

Rockfield Research Inc.

casey@rockfieldresearch.com

  • 0
    TI__Mastermind 30600 points
    Hi Jeff,

    The TLV272 is a CMOS device, so the bias current is going to roughly double for every 10 degrees C. The datasheet typical bias current is 1pA at 25C so by 45C you can expect 4pA of bias current.

    Here is a good article which discusses this is some more detail: e2e.ti.com/.../temperature-effects-on-input-bias-current-plus-a-random-quiz

    Can you describe what issues your client is seeing and why they feel the bias current of the device is the issue?

    Thanks,
    Paul
  • 0 in reply to Paul Goedeke
    Prodigy 60 points
    Hi Paul -
    Thanks for the prompt answer!
    We are seeing a discrepency between temperature measurements from different probes, and are tracking all causes. Most likely causes are physical siting of the different probes, but we are being overly cautious. I think we can eliminate the TLV272 op-amp as being causative on this, both due to the absolute bias current magnitude as well as the slope. You can consider this issue closed. Thanks much !!!
    Jeff Casey
  • 0
    Guru 140200 points
    Hi Jeffrey,

    the input bias current versus temperature plot shown in figure 2 isn't useless at all. It shows that the input bias current of this CMOS OPAmp is ultra low in your 35°C...45°C application range and only increases at higher temperatures. And there's no "slope" of bias current either. The input bias current should be rather constant.

    You write that the nominal input signal range or your application is 1V...4V. But datasheet says that the recommended input voltage range is only from 0V to VCC-1.35V, which is 0V...3.65V in your application.

    Kai