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AC Coupling INA with Integrator, while limiting current into Ref Pin

Phillip Karls
Prodigy 250 points

I'm working with an INA circuit that uses an Integrator as a high pass filter as shown in the figure below:

The same circuit is duplicated several times and the goal is to be as low power as possible. When there is a large enough differential DC voltage on the inputs, the Integrator forces a lot of current through R4 and R3. In my case, the power can be up to 10 times greater than the power at 0V differential DC. 

The current driven by the integrator is inversely proportional to the resistance of R1-R4. I have chosen an INA with a relatively low R1-R4 resistance (10k). 

Does anyone have any ideas for reducing this current or any alternative methods for AC Coupling an INA?

Thanks,

Phillip

  • 0
    TI__Genius 15410 points
    Hello Phillip,

    One option is to choose an INA with higher value R3 an R4 resistors. We can look through our portfolio and recommend a different device that meets your needs that has higher R3 and R4 resistors. What device are you currently using?

    Another option is to place capacitors in series with the input of the INA to block any DC voltage.

    -Tim Claycomb
  • 0 in reply to Tim Claycomb
    Prodigy 250 points
    Hi Tim,

    Yeah , thats the conclusion I have come to as well. I was going to try to use an INA with 10k resistors for the DA but I will probably move back to using a INA with 40k resistors.

    Thanks,

    Phillip