thank u so much ero i also use isis but i was doing a mistake that my input was too low as compare to your case i was multiplaying a 0.02m volt to gain then 0.04 ,0.06 and so that why its behaviour was non linear becoz op amp can not significant difference at output for such low input
even i use same formulas for calculation
i adjust Rf=1k ,Ri=1k nw according to formula
Vout=vin*(1+(Rf/Rin))
vout=0.02mv*2=0.04mv
nw i was expecting to 0.04 but it was the limitation of the op amp nw i understand
thank u again dear i understand it