We use a parameter called "beta" to describe the behavior of a MOSFET. The default value is small (20m), which is appropriate for a signal MOSFET. To simulate
a power MOSFET, use a larger value like 80.
In the saturation region, Ids = beta * (Vgs - Vt)2/2.
This worksheet will calculate the value of beta for a particular MOSFET, given Rds(on).