Re: resistor with mosfet
I am not exactly sure,but if you use the formula for Ron,
Tox = 4E-9 m from PSpice model of TSMC's 180nm MOSFET process(change Tox according to your model)
E0=8.85E-12 F/m ,Er=3.97 ,Cox=E0*Er/tox
Cox=8.784E-3F/m²
For a NMOS: un = 670 cm^2/(V*s)
For a PMOS: up = 250 cm^2/(V*s)
Using NMOS, unCox = 0.067*(8.784E-3) = 0.5885E-3
Ron = 1/unCox(W/L)(Vgs-Vth)
4E3 = E3/0.588*(W/L)(Vgs-Vth)
(W/L)(Vgs-Vth) = 1/4*0.588 = 0.4248.
if you use (Vgs-Vth)=0.424,Vgs = 0.824.
You get (W/L)=1
By,the way i never saw one using MOSFET as 4K resistor