Direction of AD790A bias current

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

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