Relevant equations •Id=K*(Vsg-Vth)2 •KVL
We know that Vs=0. That means Vd=-7.5 V. If we say the voltage across Rs is Vdd-Vd, then that voltage is 22.5 V. Used 22.5V/Id and got 7500 ohms.
Used the Id equation to find Vsg to be 7.5 V
Vsg=Vs-Vg, and Vs=0, so Vg=-7.5
Now, we know there are 2 unknowns, so we need 2 equations. The first equation, we used voltage division to be •-7.5=15*(Rg2/(Rg1+Rg2))
Then, the second equation was using the small signal model. The input resistance was the Parallel between Rg1 and Rg2:
•3M=((Rg1)-1+(Rg2)-1)-1 •We disregard the 10km because it is so small in comparison
This is where the problem lies. If we continue, then it leads to a value with negative ohms, which is not possible.
Any help is appreciated!