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INA2191: Requirements w.r.t. reference input, What means "capacitively coupled amplifier"

Sven Probst
Expert 1630 points
Part Number: INA2191

Dear TI -Expert,

I have two questions:

  1. Is there a reference buffer inside the INA2191? Which output impedance of the reference voltage source is acceptable?
  2. I am confused about "the INAx191 uses a capacitively coupled amplifier on the input stage", chapter 7.3.2 of document SLYS020C (datasheet). Does this mean some kind of switched capacitor network, or can it not sense DC current?
  • +1
    TI__Expert 4720 points

    Hello,

    1. There is no buffer for the reference. The input impedance is ~3.25 M ohms, the output impedance of the reference will create a voltage divider with the input impedance. Please see figure 7-4 for a typical unidirectional application circuit or figure 7-6 for a typical bidirectional application circuit. 

    2. The capacitively coupled amplifier on the front end blocks dc common-mode voltage from downstream circuits. This allows the INA2191 to reject changes in DC common-mode voltage.

    It can sense DC current. 

    If you have any other questions please reply

    Regards,

    Castrense