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OPA4377: Diode-clamped

K.Hamamoto
Guru 12155 points
Part Number: OPA4377
Other Parts Discussed in Thread: OPA377,

Hi

It is mentioned on the datasheet that the input terminal has a clamp-diode.

So that ,the absolute maximum rating of the input terminal is defined as bellow.

1. Is this spec same as the common voltage range of differential input?

2. And "0.5V" of the above maximum rating is Vf voltage of clamped diode?

3. Is there any clamped diode between +IN+ and -IN?

Best Regards,

Koji Hamamoto

  • 0
    TI__Guru 63890 points

    Hamamoto-san,

    Below please see my answers:

    1.  The input common-mode voltage of OPA377 is from a negative rail to Vcc-1.3V so it is different than the absolute maximum input voltage shown in your table.

    2.  Yes, 0.5V is the maximum allowable forward biasing of the ESD input protection diodes located between the input and each rail - any higher input voltage above positive or below negative rail requires limiting the input current to10mA or less (e.g. by adding a resistor in series with the input terminal).

    3.  There are no input protection diodes between the input terminals.

  • 0 in reply to Marek Lis
    Guru 12155 points
    Hi Marek-san,

    I am sorry for the delay in my response.

    Regarding question 3, there is the common-mode input range on the datasheet. However there is no differential input voltage range.
    Does this device have such a specification?

    In my understanding the differential input voltage range is equal to each the maximum voltage range of the each pin.
    Is my understanding correct?

    Best Regards,
    Koji Hamamoto
  • 0 in reply to K.Hamamoto
    TI__Guru 63890 points

    Koji,

    Since there is no input protection diodes between the input terminals, the maximum differential input voltage for OPA4377 is the same as the supply voltage - this means that one input terminal may be at the negative rail while the other one is at the positive rail. Having said that, op amps should NOT be used in such configuration - an inverting input terminal should always be driving by the negative feedback to be at the VIRTUAL short with a non-inverting input.

  • 0 in reply to Marek Lis
    Guru 12155 points
    Hi Marek-san,

    Thank you for the prompt reply. That is what I am thinking.
    In general, op amp does not use such a differential input configuration. (As you mentioned "an inverting input should be driving by the negative feedback to be at the VIRTUAL short with a non -inverting input.")

    I understood.

    Best Regards,
    Koji Hamamoto
  • 0 in reply to K.Hamamoto
    TI__Genius 11135 points
    Koji

    We haven't heard back from you so we assume this answered your questions. If you need additional assistance just post another reply below.

    Thanks
    Dennis