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LMV761's negative input pin is disturbed by signal on positive pin

Wayne Xu
Prodigy 450 points
Other Parts Discussed in Thread: LMV761

Below is the schematic in customer's application system. "IN" is the input for a 1MHz signal. 

When a 1MHz signal is applied on the "IN" in the front of C4. a same frequency signal is observed on the negative pin(pin 3) of LMV761. below are the test result. why the negative pin is disturbed by the signal on positive pin? where is the transmission path? is it internal or external?\

(CH2 blue signal is on "IN", CH1 yellow signal is observed on pin 3 of LMV761)

(CH1 yellow signal is on "IN", CH2 blue signal is observed on pin 3 of LMV761)

Thanks you 

  • 0
    TI__Genius 16890 points

    Hello,


    This can be caused by the scope.  Possible causes are using long ground leads on the scope probes, not having the scope probe ground leads connected at all, or having the scope probe ground connected in the wrong place in the circuit. 

    Does the output waveform look ok?

    Mike