Continue to Site

# Finding early voltage (VA) of a MOSFET using PSpice model data

Status
Not open for further replies.

#### s1a3

##### Newbie
I need to find early voltage for this circuit (PSpice 9.2 schematics) .

I already have IDS, VGS, VDS for the formula given below (in a picture). I wish to find lamda for finding early voltage (= 1/lamda).
I think W, L, VTH (= VTO) are in the data below. I am not sure where Un, Cox are.
• Is Kp down there the same KPN of the formula?
• Are all the units if the model data in SI unit?
• Is there a better way to find early voltage for the above circuit?
Model data for the MOSFET:
*BeginSpec
*XC:
*TC:
*RR: Id=-0 Rdson=0 Vgs=-10
*ZL: Idss=-0 Vds=-0
*TO: Qgd=0 Qgs=0 Vds=-50 Id=-50
*OC:
*ST: tf=0 Id=-0 Vdd=-20 Zo=5
*RD:
*EndSpec

*BeginTrace
*XC: 0,0,-0,-50,1,3,0,0,-1 (27)
*TC: 0,0,-5,10,1,3,0,0,-1 (27)
*RR: 0,0,-0,-50,1,3,0,0,-1 (27)
*ZL: 0,0,-0,-50,1,3,0,0,-1 (27)
*TO: 0,0,0,100.00E-9,1,3,0,0,-1 (27)
*OC: 0,0,-0,-50,1,3,0,0,-1 (27)
*ST: 0,0,-0,-50,1,3,0,0,-1 (27)
*RD: 1,0,-.8,-4,1,3,0,0,-1 (27)
*EndTrace

*BeginParam
*LEVEL=3 (1,4,1)
*L=2.0000E-6 (1.0000E-18,1.0000E30,0)
*W=1.9000 (1.0000E-18,1.0000E30,0)
*KP=10.150E-6 (1.0000E-18,1.0000E30,0)
*RS=70.600E-3 (1.0000E-18,1.0000E30,0)
*RD=60.660E-3 (1.0000E-18,1.0000E30,0)
*VTO=-3.6700 (-1.0000E30,1.0000E30,0)
*RDS=444.40E3 (1.0000E-9,1.0000E30,0)
*TOX=100.00E-9 (1.0000E-18,1.0000E30,0)
*CGSO=877.20E-12 (1.0000E-18,1,0)
*CGDO=369.30E-12 (1.0000E-18,1,0)
*CBD=2.1410E-9 (1.0000E-18,1,0)
*MJ=.5 (.1,1.5000,0)
*PB=.8 (.3905,3,0)
*FC=.5 (.1,5,0)
*RG=.811 (10.000E-3,1.0000E30,0)
*IS=52.230E-18 (1.0000E-18,.1,0)
*N=2 (.1,5,0)
*RB=1.0000E-3 (1.0000E-9,100,0)
*PHI=.6 (1.0000E-3,1.0000E30,1)
*GAMMA=0 (0,1.0000E30,1)
*DELTA=0 (0,1.0000E30,1)
*ETA=0 (0,1.0000E30,1)
*THETA=0 (0,1.0000E30,1)
*KAPPA=.2 (0,1.0000E30,1)
*VMAX=0 (0,1.0000E30,1)
*XJ=0 (0,1.0000E30,1)
*UO=300 (100.00E-18,1.0000E30,1)
*EndParam

*DEVICE=IRF9140-X,PMOS

* IRF9140-X PMOS model
* created using Model Editor release 9.2 on 02/15/22 at 18:49
* The Model Editor is a PSpice product.
.MODEL IRF9140-X PMOS
LEVEL=3
L=2.0000E-6
W=1.9000
KP=10.150E-6
RS=70.600E-3
RD=60.660E-3
VTO=-3.6700
RDS=444.40E3
TOX=100.00E-9
CGSO=877.20E-12
CGDO=369.30E-12
CBD=2.1410E-9
RG=.811
IS=52.230E-18
N=2
TT=140N)
RB=1.0000E-3
GAMMA=0
UO=300
*\$

You should have noticed that this is a level 3 model, using different parameters than lambda for channel length modulation modelling.

The specified IRF9140 model has no channel length modulation related parameters, e.g. Kappa and uses respectively default values which give no significant channel modulation, in other words, it ignores the effect and doesn't reflect IRF9140 behavior correctly.

Better refer to a transistor with level1 or level 2 model.

You should have noticed that this is a level 3 model, using different parameters than lambda for channel length modulation modelling.

The specified IRF9140 model has no channel length modulation related parameters, e.g. Kappa and uses respectively default values which give no significant channel modulation, in other words, it ignores the effect and doesn't reflect IRF9140 behavior correctly.

Better refer to a transistor with level1 or level 2 model.
Actually, I had no idea what level is ,and the circuit and the model is fixed in the question. The question asked me to find early voltage using IDS, VGS, VDS. I thought using the model data might do the trick. But thank you for making me aware of the significance of level.

If you have the model then you'd be best off just running the simulation at two values of Vds (both firmly within saturation region) and derive the X-intercept from the results data.

Status
Not open for further replies.