why does the voltage output of a scaler op amp configuration shift (increases) ?

[hypocritus]

Hi guys,

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?


Regards,
hypocritus

 

[frankliner]

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?