Quiescent output of a JFET amplifier

[Callum Plunkett]

Homework Statement

I am to construct a JFET amplifier with Pspice (SIMetrix) to determine the quiescent output and to compare it with my own calculations. However my calculations don’t match the simulated output by quite a margin. Can anyone point me in the right direction as I’ve had very little feedback from the uni. Electronics is really (evidently) not my strong point and its the first time I've used Pspice.

Homework Equations

ID = IDSS(1-ID/VP)2
IDSS = 10
VP = 3

VGS = -IDRS

The Attempt at a Solution

ID = 6.86mA
VGS = 1.024V

from the simulation:
ID = 3.9189ma
VGS = 6.12165V

 

[trurle]

The 2N3819 is not completely in saturation mode at gate voltage 6V. Therefore, channel current will be reduced. You need to operate at lower gate voltage (4V or such) for simplified current equation to work

 

[rude man]

It's not clear what the gate voltage is. What are the ac and dc components of Vgs?