pb with spice3f4 and ngspice
Hi,
I find a little bug in ngspice ans spice3f4.
I use the following circuit to bias a PMOS (VG<0, VD<0)
* a small circuit
M1 D G 0 0 monpmos w=5u l=1u
vd d 0 dc -5
vg g 0 dc -10
.model monpmos pmos (KP=1e-6 VT0=-3.5 )
.end
Using spice or ngspice in interactive:
----------------------------------------------------------
>source pmos.cir
>op
>show all
ngspice 3 -> show all
Mos1: Level 1 MOSfet model with Meyer capacitance model
device m1
model monpmos
id 0.0001
is -0.0001
ig 0
ib -1.93e-12
vgs 10
vds 5
vbs -0
von -3.5
vdsat -6.5
....
-------------------------------------------------
As you can see spice indicates that the vgs and vds voltages are positive !
The problem also exists with spice opus.
Any idea where is the bug ?
JM
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