Question: Here is the given solution: Now, the datasheet gives: Maximum offset voltage: 30mV Maximum input bias current: 60pA Maximum input offset current: 30pA I calculated the offset at Vout due to the offset voltage as 30mV the same as what the solutions give. I am a little confused about the offset voltage at Vout due to the input bias current however. I do not understand why he multiplied Ios_ by the parallel combination of the resistances. What I did was: Since the + terminal is grounded (superposition rule), we have a virtual ground at the node between the two resistors and since current cannot go into the opamp (golden rule). (Vout - 0)/450k + Ib- = 0 Vout/450k = -Ib- Therefore Vout = -27uV due to the maximum bias current Whereas they seemed to use the total parallel resistance and get 2.7uV Please explain?