Inspite of all the compensation techniques the output voltage is still not zero with zero input voltage.
Hence a small voltage is applied at the input terminals to make output voltage zero which is called as input offset voltage.
The following are the non-inverting and inverting amplifiers respectively:
Where V1 =0 gives
Voltage V2 is given by
V2 = V0 [R1/(R1+ Rf)]
Or V0 = V2 [ (R1+ Rf)/ R1]
Since, Vios = │V1 – V2│and Vi = 0
Vios = │0 – V2│ = V2
V0 = [1+(Rf/R1)] Vios