[Ngspice-users] Newbie question on simulating a mosfet inverter

[Daniel C. H. <dan...@gm...>]

Hello,

I'm new to electronics and spice and I'm trying to simulate a simple
nmos inverter but my setup just doesn't seem to work. When I run the
simulation the output voltage stays at high level with some very small
spikes when the input changes (I guess this is due to the parasite
capacitors in the mosfet model). The only warning that ngspice gives
is that there is no level set for the mosfet, but seting the level to
1, 2 or 3 didn't solve the problem.

The input file I'm working on is this

Title Trying to use MOSFET's in simulation

.INCLUDE 2N7000.mod

Vgs in 0 DC 5 PULSE 0 5 0 100u 100u 1m 2m
Vdd dd 0 DC 5V
R1  dd out 5k
* Zetex
Xmos out in 0 2N7000

.CONTROL
run
tran 10u 10m 0 10u
plot v(out)
plot v(in)
.ENDC

.END

The MOSFET model I'm using can be found here
http://www.google.com/url?sa=t&ct=res&cd=1&url=http%3A%2F%2Fwww.zetex.com%2F3.0%2Fspice%2F2n7000.mod&ei=3gyKRYLtN4r2owLJ07SDDw&usg=__qD8BjNuCMI0VRztaP1SyJsusTb4=&sig2=D5dbHUWYoEe-1DeBVpauiA

The datashet is here
http://www.google.com/url?sa=t&ct=res&cd=2&url=http%3A%2F%2Fwww.zetex.com%2F3.0%2Fpdf%2F2N7000.pdf&ei=3gyKRYLtN4r2owLJ07SDDw&usg=__9cXuGI67A1xQyzF-qIboRlcgMqA=&sig2=bZ1TCMt4tMEnXWYEk88FxA

And the circuit I'm trying to model is this one
http://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-002Circuits-and-ElectronicsFall2000/F0B2D731-3CBF-4762-851F-5299800C5300/0/demo07.pdf

Any help would be greatly appreciated.

Daniel Cabrini Hauagge