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Amplifying (nano-micro ampere) using LPV812 Dual Channel 425nA Precision Nanopower Operational Amplifiers for sensor application

Hi, im trying to build a ultra-low current reader using arduino and INA219 for my sensor device. Anybody can help me to explain whether it is possible to create ultra-low current sensing device by adding LPV812 op amp amplifier? i need to know before purchasing it. thank so much forum members. below is the example of circuit that i want to build.

  • Hello Adzhri,

    The INA219 will not work for this application because the input bias current (~20uA) is of the same magnitude of the current you're trying to measure. I recommend using an op amp with a small input bias current. While the LPV812 does have a small input bias current (100fA typical), the input common-mode range is 0V<Vcm<2.4V. Since you're looking at using low-side current sensing where Vcm=~0V, you will be on the very edge of the linear operating region. Therefore you may want to consider an amplifier like the OPA320. You can search for other op amps using the following tool. Just remember that you're most important specifications are input common-mode voltage, input bias current, and input offset voltage.

    www.ti.com/.../OPAMPS-SELGUIDE

    If you need to change the gain because of the range of the load current, please consider using a dual supply and a PGA. I recommend evaluating the FET-input PGA206/7.

    Regards,

    Pete Semig

    General Purpose Amplifier Applications