[SI-LIST] Re: hspice issue
- From: Yu Liu <yu_liu@xxxxxxxxxxxxx>
- To: mike_bihan@xxxxxxxxxxxx
- Date: Mon, 13 Jan 2003 10:27:56 -0800
Han Bi,
I can not tell you whether hspice takes "the time for electron to across
the channel" into account or not, because I have no experience with
hspice. However, as I said, BSIM3v3 model took into account of the NQS
model by means of the first-order Elmore delay. However, several
approximations are made in the model, especially the bias-dependency of
the relaxation time, as well as the ignorance of bulk charge. So in
short, BSIM3v3 (and in that respect, BSIM4) does model the NQS effect,
which includes the limited carrier speed (drift current) across the
conducting channel. However, whether that model gives you satisfactory
result depends on your application.
I would suggest some readings on the NQS model: A BSIM3 manual (from
UCB) is a great source to learn the modern MOSFET device modeling. There
are also some excellent books from Yannis Tsividis and Daniel Foty.
Regards,
Yu
===
Bi Han wrote:
> would you like to tell me that whether hspice take "the time for electron to
> across the channel" into account?
>
> Thanks, Bi, Han
> Yu Liu <yu_liu@xxxxxxxxxxxxx> wrote:Hi, Bi Han,
>
> This is a device modeling issue, in particular the so called
> Non-Quasi-Static (NQS) model. Most of the device models in SPICE are
> Quasi-Static (QS) model, assuming instant device current response w.r.t.
> the corresponding bias. However, BSIM3 model has added some NQS
> modeling capability so it can exhibit some NQS effects.
>
> Hope this helps.
>
>
> Yu
> ===
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>
> Bi Han wrote:
>
>
>>Hi, all:function SetDomain(d) { document.domain = d; }
>>
>>Did hspice included the variation of gm (CMOS) over broad frequency upto 20G ?
>>
>>Since it takes electrons finite time to pass through the channel, so there
>>will be a up-limit frequency which eletron will forever stay in the channel.
>>
>>Did hspice take that into account? In another way, if no parasitic
>>capacitance exists, will the cut-off frequency of mosfet in hspice simulation
>>be infinite ?
>>
>>(The reason I did not do the test it myself is that it looks that impossible
>>to remove all cap in the process file, maybe some avanti guies can answer
>>this problem.)
>>
>>
>>
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