Apparent resistance of a MOSFET?

[magician13134]

Hello, I'm stuck on a homework problem where they ask us to determine the apparent resistance of a MOSFET given a set of data plotting V_DS (voltage from drain to source) against V_GS (voltage from gain to source). I don't really have any idea how to do it. In addition to the data, we're given the circuit. Any help is much appreciated, thanks.

 

[RCinFLA]

Simple ohms law. Given Vdd, Vr, and Rload, figure current through load resistor and Vds. Rs of MOSFET equals Vds/Id.

 

[magician13134]

Oh, that makes sense. Thank you.
Now, I have one more, very similar question that I can't quite finish...

From this, I have gotten three unique equations:
[LATEX]V_R = I_LR_L=V_d_dR_L/(R_L + R_E)[/LATEX]
[LATEX]V_D_S = I_LR_E=V_d_dR_E/(R_L + R_E)[/LATEX]
[LATEX]I_L =V_d_d/(R_L + R_E)[/LATEX]
(which is the same as the fourth)
[LATEX]R_E=V_d_d/I_L - R_L[/LATEX]

We're given [LATEX]V_d_d = 6V[/LATEX] and [LATEX]R_L = 200Ω[/LATEX] but we need to find four unknowns [LATEX]V_R, V_D_S, I_L, R_E[/LATEX] so I can't figure out a fourth equation... Any ideas are greatly appreciated. thank you

 

[RCinFLA]

Need another value. Ids (or load IL) Which will be a function of Vgs for the particular MOSFET.