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TL084: Differential input voltage

Prodigy 60 points

Replies: 8

Views: 109

Part Number: TL084

Dear Sirs,

I would like to know, how the TL084ID operational amplifier reacts if the max. differential input voltage is temporarily exceeded when connected as a comparator (sine-delta comparison).
Is there a phase reversal or can there be a defect?

  • Hi Manuel,

    when violating the absolute maximum ratings you risk that the TL084 gets damaged.

    You could clamp the input voltages against each other with diodes (BAV99 or similar). Or you could use a regular comparator.

    You might want to post a schematic?

    Kai

  • Hello Manuel,

    This device may exhibit phase reversal when operated outside of the recommended operating conditions.  Typically, phase reversal is associated with operating the common mode input voltage outside of its specified operating conditions.  Depending on your scenario, this is a possibility.

    More importantly however, you certainly risk damaging the device when you violate the absolute maximum ratings.

    Regards,

    Daniel

  • In reply to kai klaas69:

    Hello Kai,

    thank you for your fast answer.

    Here is the schematic:

    V6 is the TL084.
    The sine triangle voltage is compared at pin 9 and 10.
    There is a sine voltage on V6: Pin 9 and a triangle voltage on V6: Pin 10.

    The sine voltage level is around 14 V. The triangle amplitude is about 15,0 V because of rail to rail OP AMP OPA4197IDR (V5 and V15)

    Best regards

    Manuel

  • In reply to Manuel Christ:

    Hi Manuel,

    I don't think you are violating the absolute maximum specs.  However, what supply voltages are you using?  I would encourage you to read through this forum thread to learn more about using the device as a comparator.

    Regards,

    Daniel

  • In reply to Manuel Christ:

    Hi Manuel,

    I don't think you are violating the absolute maximum specs.  However, what supply voltages are you using?  I would encourage you to read through this forum thread to learn more about using the device as a comparator.

    Regards,

    Daniel

  • In reply to Daniel_Miller:

    Hello Daniel,

    we use +/- 15 V as supply voltage. I also did some measurements of the differential voltage.

    The voltage was about 28 V, so its near the maximum, but didn´t violate the maximum voltage.

    Thank you for the thread.

    Best regards

    Manuel

  • In reply to Manuel Christ:

    Hi Manuel,

    hhm, aren't you violating the common mode input voltage range of TL082? Why not using two identical voltage dividers at each input of TL082 (pin 9 and pin 10)?

    Kai

  • In reply to Manuel Christ:

    Manuel,

    Kai brings up a good point here as shown from the data sheet below.

    Since the original question has already been answered, I will go ahead and close this.  But if you have follow-up questions or need help, you can either create a new thread or respond here.

    Regards,

    Daniel

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