In the datasheet for the AD8638 I don´t understand how the input offset current can be much larger than the inbut bias current.
E.g. on page 4 of the datasheet at the specs for V(sy)=16V there is 1pA/75pA (typ./max.) input bias current at 25°C, but 20pA/70pA (typ./max.) offset current.
How is that possible and why is it so?