Mike,
Thanks for your exhaustive response. I'm actually a graduate student
at Stanford University. My goal, or rather my professor's goal, is to
look for potential new tools to replace the cumbersome Hspice and
Avanti Awaves combo. The level 3 model is only the model used in one
particular class. Using our level 49 BSIM model for the Op Amp I
gave, I was able to obtain almost identical results from LTspice and
Hspice. So I will definitely recommend LTspice to my professor and
hope to convince to drop the level 3 model. :)
Thanks again,
Hao
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--- In LTspice@..., Panama Mike <panamatex@y...> wrote:
Helmut,
I am in a discussion about modeling of an opamp with
MOS Level-3 transistors in the YAHOO-LTSPICE-Group.
After some xperiments, I asked Hao for the result of
a simple inverter simulation (Hao_inv.cir,
transistors.txt). The result of I_drain(M1) looks
quite different in HSPICE. Could you test it with
other simulators. At the moment there is some
belief that the LTSPICE Level=3 model is not correct.
Please put your answer into the YAHOO-LTSPICE group.
Yes, there is a problem for mos3 ETA being very small.
It looks like it works fine if ETA is around 1.(which
is where MOS3 was designed to operate) and it's okay
if ETA is zero. But other than that it's something of
an odd ball the fixes to the Berkeley device apperar
to be non-standard. I'm close to a solution on that,
in that I've identified one error in the way the Jacobian
is computed in Berkeley spice, but haven't finised it
to work with all permutations of the other mos3
parameters.
BTW, LTspice does okay with practical MOS3 models.
MOS3 is something of an obsolete MOS type, so I don't
know if I'm going to be able to spend enough time on
it to completely fix it for all models. The device
is nolonger of real use. At least I don't know of
any IC's designed today with mos3 device models.
Another question:
I haven't seen any minor update since more than a week.
Is LTSPICE still alive?
Yes, of course. I've been swamped preparing a new release
that contains two solvers, one with a new sparse matrix
package that can solve those pathological PSpice style
opamps models like Stuart Brorson's OP177A opamps circuits
with no problem. I expect that release out in less than
two weeks. BTW, the new version is quite a lot larger
executable, over 4Megbytes. Even larger if I compile
in support for Pentium 4 instructions(since it still
needs a copy of the AMD code for backward compatiblity)
It could end up close to 6MB instead of 3MB.
I'll anounce here when this version is availible.
--Mike
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