Threshold values of mosfets

[akchetana]

Hai,
I wanted to know the exact values of threshold voltages of mosfets that the cadence tool uses for simulation. It is not clear from the model file. How do I get those values?
Thank you.

 

[vadim888]

Hi,

you have various options to find Vth in cadence,
but I prefer this way.

1. Make DC analysis (save OP point)
2. Go to schematics:
View/Annotations/DC op points

and you will find out Vth for each transistor.

Best,
Vadim

 

[akchetana]

Thank you so much.
However I already knew this approach.
Is there any way by which we can find it from the model file?
Thanks once again.

 

[dick_freebird]

Have you looked at your model file? Modern compact
models have too many layers to just dope it out from
one (VT0) param, there's all kinds of second order and
geometry dependent actors. You could read the model
manual and follow the math using what you find in the
model and process params include-chain. Sound like
high-probability-of-success fun? Take the simple advice,
is my advice.

 

[erikl]

Is there any way by which we can find it from the model file?

You can find it directly in the model file as Vt or Vth0, different for NMOS and PMOS of course. But this is just a special value of an Operation Point (OP) defined in the BSIM definitions. This OP is somewhere at the onset of drain current, in the center of the weak inversion mode, i.e. at an Inversion Coefficient IC≈1. For all other OPs Cādence Virtuoso tools will report a little bit different values.