Dear Sykab,
Your PDK do***entation (DRM, Electrical Rule Manual ...) should tell
you the allowed voltages on each node of each transistor.
A kind of data-sheet that tells you for example :
VGS(NMSO1) =3D 3.3v +/- 10%
VDS(NMSO1) =3D 3.3v +/- 10%
=2E... etc
As St=E9phane explained, the Voltage you put on the transistor's gate
depends on the Oxide thickness (Tox), The thickest it is, the more
voltage it sup****ts.
But, what really happen if you put 5V on your transistor that sup****ts
3.3V ?
In the real world, your transistor will burn up on die ... In the
simulation world, it may work, it may not, depends on how your model
has been derived.
When I was working with the STMicroelectronics PDK using Eldo (Mentor
Graphics Simulator), the Spice Model cards used to come with Safe
Operating Area Checks statement, something like :
=2Esetsoa label=3D"VGS out of range" e V(G,S)=3D(-2.75,2.75)
So when you simulate your design including the Check of Safe Operating
Area (. checksoa eldo command in you netlist), the simulator raises
warnings/errors if your VGS exceeds the defined limits at some point
during the simulation. This is the kind of range checking that helps
designers in avoiding any unlucky biasing.
I know that spectre sup****ts a similar thing but I prefer to send you
to the Spectre doc since I have never used it myself :
-> Virtuoso=AE Spectre=AE Circuit Simulator UserGuide -> Control
Statements -> Assert Statement
Andrew can tell more about this.
Cheers,
Riad.
|
