Hi,
   I am trying to model the output voltage variations due to the varying input common mode DC voltage for an OPAMP (for DC simulations) in verilogA. As I understand, the OPAMP would work in desired manner in the range (Vin_CM_low to Vin_CM_High). Above or below this range the output would saturate.

    I have problem in modeling the output for in-between range of input CM voltage i.e., between (Vin_CM_low to Vin_CM_High). If I can use a "sigmoid function" [1/(1+exp(-x))] as a solution for this, what parameter of the OPAMP controls the slope of the sigmoid funtion.

Thanks in advance,
Packiaraj.V.