What is the On Resistance, RDS,on of a FET Transistor?

The On Resistance, RDS,on, of a FET transistor is a built-in parameter of the transistor that represents the transistor's internal resistance when it is in its fully conducting state (when VGS=0).

Typically, the on resistance, RDS,on, ranges between 10Ω to 1000Ω.

This resistance value is provided in the specification tables of FET transistors.