Categories

# Why does the datasheet only has one input bias current value?

There should be two input bias currents, one flowing into or out of the inverting input and the other, the non-inverting input. Their difference is the input offset current. A typical datasheet only states one value for the input bias current. Is that bias current going into the inverting or the non-inverting input? Or is that an average of the two input bias currents? Or perhaps something else no specified on the datasheet?

If I assume $$\ I_{B+} = 600 \text{nA} \$$ and $$\ I_{B-} = 400 \text{nA} \$$ then I would get an average value of $$\ 500 \text{nA} \$$ and a difference value of $$\ 200 \text{nA} \$$. The calculation matches the values on the specification sheet where input bias current = 500nA and input offset current = 200nA. The leads me to assume that the single input bias current value provided on the datasheet is actually an average.

A similar question was asked here Input bias current in an opamp and its value in a datasheet but I can’t find a relevant answer there or elsewhere on the web.