Help to plot threshold voltage of MOSFET

[Siew Kuok Hoon]

Hi,
I want to find out if there is such a function on Cadence that :
I could plot the vth (threshold voltage) of the transistor versus the
gate voltage of the transistor (MOSFET).

I know how to check the vth (threshold voltage) of a MOSFET using the
analog artist "print DC operating point", but it is only for a single
operating
point. I hope I could find such a function on the "calculator" in the
analog artist, so that I could use it for the Monte Carlo analysis.

Thanks,

[James W. Swonger]

In article <37165821...@ee.tamu.edu>,

You can use the parametric analysis tool and step Vgs, and then
plotting the OP(Mxxx,VTH) result with the calculator will give
you what you want.

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#Irresponsible rantings of the author alone. Any resemblance to persons #
#living or dead then yer bummin. May cause drowsiness. Alcohol may inten-#
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[Siew Kuok Hoon]

Hi James,
Your method works !

Another question :

How to perform Monte Carlo analysis when I'm using the BSIM3 version 3
model card ? I use the 'include environment' function to include the
model card of BSIM3.
For SPICE level 2 model card, I just need to specify :
VTO=GAUSS(0.7339,48.92667e-3,2), and then run the monte carlo analysis
to check the performance when transistor is subjected to a gaussian
variation of VT0. What about BSIM3 ?

Thanks!

[Andrew Beckett]

As an alternative to using a parametric sweep, use a normal DC sweep,
and put the following in an include file (I'm assuming you're using spectre):

save m1:vth

(where m1 is the instance name of the mosfet).

This tells spectre to save the vth output parameter of the mosfet over
the sweep, rather than just at the op point.

This runs much quicker than parametric (although parametric is pretty fast in
4.4.3)

You may need to use the results browser to access the data, though.

Andrew.

On 16 Apr 1999 12:52:52 GMT, j...@billy.mlb.semi.harris.com (James W. Swonger)
wrote:

>In article <37165821...@ee.tamu.edu>,
>Siew Kuok Hoon <hoo...@ee.tamu.edu> wrote:
>>Hi,
>> I want to find out if there is such a function on Cadence that :
>> I could plot the vth (threshold voltage) of the transistor versus the
>> gate voltage of the transistor (MOSFET).
>>
>> I know how to check the vth (threshold voltage) of a MOSFET using the
>> analog artist "print DC operating point", but it is only for a single
>>operating
>> point. I hope I could find such a function on the "calculator" in the
>> analog artist, so that I could use it for the Monte Carlo analysis.
>
> You can use the parametric analysis tool and step Vgs, and then
>plotting the OP(Mxxx,VTH) result with the calculator will give
>you what you want.
>
>
>--
>##########################################################################
>#Irresponsible rantings of the author alone. Any resemblance to persons #
>#living or dead then yer bummin. May cause drowsiness. Alcohol may inten-#
>#sify this effect. Pay no attention to the man behind the curtain. Billy!#

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