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Question for OPA buffer

Brian Wang0928
Genius 14020 points
Other Parts Discussed in Thread: LMV321, TLV341

Customer uses a uni-gain buffer to do a voltage sensing with the baterry cell.

When the R993 resistor is removed(it means the positive terminal of the LMV321 is floating), the output voltage of LMV321(U990) will output 4V. Why? How to prevent this by effective way? any other good OPA recommended to improve it?

We tried to add a Resistor 10M-Ohm connected in between positive terminal of LMV321 and grounding. it can reduce the output voltage of LMV321 to 0.8V, however, it is an efficiency killer that customer doesn't prefer to do it. Thanks.

Regards,

Brian

Regards,

Brian

  • 0
    TI__Guru**** 164396 points
    Brian,

    The LMV321 has a input bias current that flows out of the LMV321. So it "floats" high by itself.

    TLV341 has CMOS input so the input current is practically zero.
    However with a floating input who knows what output will be?
    100M to ground should be OK.