So I am using LM318N op amp in inverting scaler configuration: Vin=3.3V, Rf=100kΩ, Rin=820kΩ in order to scale the input to get -0.4 V output, all is fine. However, the output wasn't -0.4V, but it shifts to and fluatuating around -0.683V. Would you guys kindly tell me what you think might be the problem?
The input bias current is pretty high, and your resistors are pretty large so that may be the problem. Do you have an input bias compensation resistor of RF||Rin?