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LM358: LM358 is suitble to amplifier 0~50mV signal

Lin_Charles
Expert 4260 points
Part Number: LM358
Other Parts Discussed in Thread: TLV9002

Hi, all

I want to use LM358 to amplifier the input voltage signal: 0-50 mV. And I choose the LM358 for its low cost. Here is my question:

  1.  Signal frequency is 10 Hz. If my requirement of voltage solution is 1%, does this amplifier satisfy this requirement? Or what specs should we consider when consider this amplifier is suitable of not.
  2.  If we use LM358, should we consider  a high accuracy requirement for resistance.
  3.  Is there need to calibrate the system when the product is put into market.

  • 0
    Guru 140200 points

    Hi Charles,

    as the LM358 is no output rail-to-rail OPamp the output won't go down to exactly 0V.

    By the way, why not amplifiying already in the first stage?

    Kai

  • 0 in reply to kai klaas69
    TI__Mastermind 30600 points
    Hi Charles,

    I see from your schematic that you can use a power supply range of 5V to 10V. If your design allows you to use a 5V supply, I would recommend the TLV9002 instead of the LM358. It is RRIO, higher BW, lower Vos, etc.

    The LM358 has a much higher input offset voltage will contribute substantially to the error in your current configuration. Like Kai asked, why are you putting a unity gain buffer in front of your gain stage? If you don't need that buffer, you'll be able to minimize the errors from having two op amps.

    As far as key specs for accuracy, look at the Vos and Ib. I would also recommend that you look at the TI Precision Labs videos, section 2: training.ti.com/ti-precision-labs-op-amps-vos-and-ib

    The need to calibrate will depend on how much error can be tolerated and your choice of other circuit components and their ability to vary. If you know that your components are tight tolerances and your input is highly predictable, then you can safely assume that your output will be acceptable without calibration. But it is difficult to say at this point.

    Hope that helps,
    Paul