Direction of AD790A bias current

Hi,

The AD790A bias current is 2.5(Typ)/5(Max) according to the data sheet.
I suppose the AD790A bias current flows into the device as with any simple NPN differential input stage.
Is that right?

Best regards,

Nikkee

  • Nikkee,

      Unusual question.  Why does it matter in your system?  What are you doing?

    IVR in spec table implies PNP input stage, so current flows out.

    Harry

  • Hi Harryh,

    Thank you very mach for your quick reply.

    I understand that + mark means the bias current flows into and

    - mark means the bias current flows out of the device in your datasheets

    which means the AD790 bias current flows into.

    And we have received a question of AD790 bias current direction from our customer.

    They says that the AD790 bias current flows out of the device in their system.

    So I posted the thread.

    Best regards,

    Nikkee

  • Nikkee,

      Most data sheets for op amps, comparators, etc. for offset voltage, input bias current, etc. simply

    have a number with no + or - sign.  For offset voltage, 1 mV means +/-1 mV.  For bias current,

    IF there is only one input diff pair, the current will be in one direction, but is usually not speciifed,

    so 1 uA could be + or -.

    For rail to rail input op amps, such as the OP291, it can actually reverse, depending on which input

    pair is working.  See figure 12 on the OP291 data sheet.

    Why is the direction inportant?  Must be an unusual circuit....

    Harry

  • Hi Harry,

    We must reply to customer questions, so I asked here about it.

    I think there is no special meaning.

    Best regards,

    Nikkee

  • 0
    •  Analog Employees 
    on Aug 2, 2018 2:39 PM
    This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

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    EZ Admin