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?
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....