Hi Hassan,
This is the warning message other than error message. There are two warning message here:
1. "Estimated output characteristic gradients for data extrapolation must be greater than zero. Use linear extrapolation." We typically use a threshold-based equation to assist with extrapolation to prevent excessively large values for the current and to ensure the MOSFET is saturated, rather than always in the linear region when the data is insufficient, as in this case for Vgs=7V or Vgs=10V. If this approach is not successful, switch back to linear extrapolation. If you would like to use linear extrapolation, you can just leave as it is, it will be used as is.
2. "At time 1.614255e-19, one or more assertions are triggered. Tabulated drain-source currents, Ids(Vgs,Vds), have resulted in a current opposing the applied voltage. Consider modifying the tabulated data to ensure that all operating points are contained within the data and that the signs of the currents and voltages are consistent. Clipping the current to zero." This warning message usually indicates that the MOSFET does not have a clear threshold showing when it is on or off. To avoid this message, it is suggested to add Vgs data near the threshold.
