may you share with me your j201 parameters for simulation please? i use LTSpice, but i think spice parameters are the same for both softwares...

Sure!

The three JFET models I use are:

* J201 with VGSoff=-0.8V and IDSS=0.6mA

.MODEL J201 NJF (VTO=-0.8 BETA=0.94M LAMBDA=2M IS=114.5F RD=1 RS=1

+ CGD=4.667P CGS=2.992P M=.2271 PB=.5 FC=.5 VTOTC=-2.5M BETATCE=-.5

+ KF=604.2E-18)

* 2N5457 with VGSoff=-1.6V and IDSS=3.3mA

.MODEL 2N5457 NJF (VTO=-1.6 BETA=1.29M LAMBDA=2M RD=1 RS=1 CGD=6E-12

+ CGS=2.25E-12 KF=6.5E-17 AF=0.5)

* MPF102 with VGSoff=-2.5V and IDSS=6mA

.MODEL MPF102 NJF (VTO=-2.5 BETA=0.96M LAMBDA=5M RD=1 RS=1 CGD=1.54248P

+ CGS=2.567P PB=1.49 KF=7.90591F AF=499.953M)

Your J201 model is a little on the high-gain side, but perfectly reasonable, as it has VGSoff=-0.6V and IDSS=0.58mA.

My model has a little less gain as it is representative of the average of a lot of units I measured.

Just in case you are wondering where did I pull the 0.58mA: IDSS= BETA * (VTO^2).

So, if you want a JFET with a certain value of VGSoff and IDSS, just change the model so:

VTO = VGSoff

BETA = IDSS / (VGSoff^2)

Other parameters are less relevant. For instance, LAMBDA accounts for the Vds effect on the drain current. As it is a very small value, it doesn't produce any significant effect unless you are powering your circuit with 50 volts or more.

Other parameters model parasitic capacitances (which affect behaviour at high frequencies), or model temperature dependency.