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XSpice codemodeling for dummies?

Discussion in 'CAD' started by Stuart Brorson, Sep 12, 2003.

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  1. Hello,

    I will need to create a model of a semiconductor device based upon its
    physics -- that is, based upon the constituitive relations,
    depletion lengths, Fermi levels, and all that other junk you find in
    Sze. I am probably going to do it using an XSpice codemodel.

    I am kind of confused about how I can model the C(V) behavior
    of the device, because as far as I know the IOs provided by a
    codemodel only allow you to input/output voltages and/or currents, and
    I don't know how to put in time information (i.e. to support the
    differentiating behavior of the cap).

    Is anybody here aware of a good text-book which would illuminate
    the internal workings of SPICE, and provide a guide to extending it
    using XSpice codemodels? I have looked at a few on-line theses and
    such, but I need something more like "codemodels for dummies".

    Any suggestions?

    Stuart
     
  2. No, there is a general integrator method.
    Copy and extend the code in cml\capacito\cfunc.c

    i.e. use

    cm_analog_integrate(private->conn[0]->port[0]->input.rvalue /
    private->param[0]->element[0].rvalue, vc, &partial);

    Formulate all equations in terms of integrations.
    I assume you have the xspice manual,
    http://www.anasoft.co.uk/xspice_pdf.zip
    No chance. XSpice code modelling is very specialised. Sure, most of the
    main vendors use XSpice as a base, but there are only about 20 of them,
    so how many engineers do you think that are actually familiar with
    detailed XSpice code, considering there are millions of generic MS
    visual++ programmers?

    Realistically, your going to have to plough through the code yourself to
    figure out how it works.

    Try a different problem:)

    Or, copy an existing set of files from the Spice3 part, and modify the
    equations.

    Kevin Aylward

    http://www.anasoft.co.uk
    SuperSpice, a very affordable Mixed-Mode
    Windows Simulator with Schematic Capture,
    Waveform Display, FFT's and Filter Design.
     
  3. Stuart,
    It's probably much easier to just write this type of spice device
    without using xspice. That's been my experience anyway. Integration
    of the general non-linear capacitance isn't too hard to figure
    out. LTspice has an arbitrary capacitance device that is useful for
    rapid prototyping new charge models. I'm not much of a fan of xspice
    and I have not seen it used by the major SPICE programs like LTspice,
    PSpice, hspice, or Spectre.
    There's various books on how SPICE works, the 2nd edition of the one
    JT suggests is one I always recommend and you will need, but doesn't
    address SPICE internals. A good one there is the one by Pillage and
    Rohrer. I've been thinking of writing one myself, but until then
    you should just get every one you can find if you want to get involved
    in this. It's a interesting endeavor. You'll find yourself in club
    smaller than the number of people that walked on the moon.

    --Mike
     
  4. Obviously, since your experience is not with xspice, it would be much
    easier, with your experience, to write new models in the method you
    already know.

    In principle, once the learning curve has been done, its much more
    easier, to add device models in xspice using its code modelling feature,
    then it is in Spice3. For starters, instead of the 20+ files of Spice3
    for a model type, there are only two c files, and one of these are
    generated automatically by a model port specification file and an xspice
    specific helper program. The fundamental feature of the xspice code
    modelling was that is was designed for easier addition of new models. It
    has a very systematic, general way of doing so.

    Integration
    This depends on how one defines major, and how observant some particular
    individuals are. HSpice and Spectra, while much used in the i.c.
    industry, has a relatively low numbers of users, in part based on the
    $50k type cost of such Unix based products, and the relatively few
    numbers of i.c. designers compared to board level designers.
    Spice3/XSpice have 100,000's of users, so is indeed a major spice
    platform. As as been pointed out, EWB claim the most customers in the
    known universe for their XSpice based product.
    Good. I look forward to your book. I hope you include your secrets for
    simulation speed up so I can use them myself.

    Kevin Aylward

    http://www.anasoft.co.uk
    SuperSpice, a very affordable Mixed-Mode
    Windows Simulator with Schematic Capture,
    Waveform Display, FFT's and Filter Design.
     
  5. Kevin,
    You are mistaken. I do have xspice experience. I was once
    associated with a SPICE vender who's product was xspice based.
    My disdain for the code and it's methods is firmly based in
    extended experience with it. The mixed-mode simulator and HDL
    used in LTspice came after a moment of clarity that dictated
    an entirely different approach and subsequently throwing out
    all of xspice.
    Yes, that was the goal. It's good you've come to understand
    the xspice mission. I've seen people selling xspice simulators
    that didn't know that the mixed-mode simulation capability
    was a demo of this feature. But at the end of the day, I see
    xspice as a failure of that goal. For me, there's too many
    things to do in the rest of the simulator when new device types
    are added. E.g., LTspice uses a much more flexible organization
    that allows circuit and matrix manipulation beyond what
    spice3f5/xspice allow.
    Major demands some respectability. LTspice, PSpice, hspice,
    and Spectre command that in my view whereas EWB does not
    command the same level of respectability. It's IC designers
    that really test the SPICE's. I don't think too much of a
    SPICE that can't do reliable transistor-level full-chip
    simulation. The academics codes can't do that out without
    extensive re-thinking and work. If user-base by and of itself
    means anything, LTspice is downloaded every 5min., 24hrs a day,
    365.25 days a year, for the last few years, not even including
    updates(The Tools=>Sync release command) and downloads from
    cached sites at universities for course work. That also
    doesn't count that LTspice is also widely redistributed on
    third-party CD's, like one last year that went out with a
    German electronics magazine and other collections of freeware
    EDA software. I think any estimate one could make on the
    number of distributed copies would beat a minor(in my opinion)
    SPICE like EWB.

    --Mike
     
  6. I don't deny this. I meant to point out that you have spent considerably
    more time writing and developing code for non xspice based simulators.
    As you note below, you throw the xspice code away. This means it is de
    facto more easier for you to make additions to non xspice based code.
    It certainly missed doing a check on fopen() when reading a state
    description file. It proceeded merrily alone blissfully unaware it was
    using a null file handle. The state machine code I got didn't actually
    work at all until I fixed it, maybe:) It didn't allocate memory for
    some of its arrays.
    Although, in practice, its not that often that one really needs to add a
    new device. New features can be quite nice though. Have you figured out
    how my DeviceDesigner feature works yet? Not that I will admit to any
    method in public, even if guessed at correctly.

    Actually, the xspice capacito code, as is, doesn't work either. It puts
    a s/c on its terminals for dc operating point and initial transients. I
    was going to add in esr to it, couldn't be bothered after I realised
    that I would have to fix this issue as well. I'm just going to add new
    features, the basic engine has more than enough for 99% of users.

    Oh. yeah, I had to add in an end resistance parameter to the xspice pot.
    Setting the rotation to 0 or 1 on a schematic, yep you guessed it,
    divide by zero:)

    E.g., LTspice uses a much more flexible organization
    I dont really agree with this. There is only one real applicable
    definition of major in the commercial world. This is net sales/profit.
    Porn videos can hardly be called respectable in a pure sense, but its a
    $billion market, with is indeed a respectable figure.
    What about Simetrix, or Intusoft's IsSpice which are both based on
    XSpice. Both claim major improvements to the speed and convergence. I
    believe they both claim full ability to run the standard benchmark
    circuits.
    Indeed. However, this still does not negate that fact that i.c designers
    make up, probably, < 1% of all spice users.
    Most board level designers, in general, don't need the ability to
    simulate 10,000 transistor analogue circuits, so its a particular view
    that is not important these particular engineers.

    This is really one of an engineering idealist/perfectionist, verses the
    practicalities of what is really required by the majority of the market
    place.

    The academics codes can't do that out without
    This is indeed a well reasoned argument, but it somewhat missies the
    point of the original post I think. Indeed, once the source code for
    LTSpice, PSpice, HSpice or Spectre is released to the public so that
    individuals who want to add their own models to a Spice are abe to, this
    argument might well have same merit. However, in the absence of such
    facilities, there is only one, rational, practical choice available,
    that is to use either the Spice3 or XSpice code, which is, of course,
    freely available. The XSpice being the better choice because it includes
    all of the Spice3 code, fixes the removal of poly(), plus has some more
    useful features to boot.

    Kevin Aylward

    http://www.anasoft.co.uk
    SuperSpice, a very affordable Mixed-Mode
    Windows Simulator with Schematic Capture,
    Waveform Display, FFT's and Filter Design.
     
  7. Kevin,
    The point is make you claims in complete ignorance and
    make false asserts of other's knowledge. My opinion that
    it's easier to add a new semiconductor device to spice3
    than xspice is based on extensive experience with each.
    That shows.
    But LTspice top's the list of SPICE's by your commercial
    definition. SPICE is small industry, so many millions
    per year -- not billions. LTspice has helped sell
    billions of SMPS products and has be called the most
    successful piece of sales collateral in engineering
    history. Does LTspice's superlative commercial success
    mean only what I say is correct and whatever anybody else
    says is incorrect? Citing commercial success is not a
    convincing point in technical matters.
    I've not evaluated Simetrix, but years ago I did evaluate
    IsSpice. Benchmarks quickly indicated those claims were
    baseless. I still have images of Intusoft's V.P. frothing
    at the mouth at a DAC conference when confronted with
    this. He insisted that all SPICE's used the same code
    and ran the same, just like you used to and so many other
    junk SPICE vendors who command no respect in my opinion.
    Of course not. SPICE's that can't do difficult IC simulation
    give move problems doing board-level simulations. There exist
    independently collected IC benchmarks in academia. There isn't
    this established culture for the for board level simulation.
    Of course, just because a SPICE does the best at IC simulation
    doesn't mean it will necessary be the best for board level.
    You'll note that many people in this usegroup like LTspice for
    board level simulations because it can run PSpice macromodels
    and semiconductors, something that xspice can't. The standard
    for macromodels PSpice syntax, an enhanced language of
    spice3 and not part of xspice.
    Between spice3f5 and xspice, xspice is bigger and harder to
    understand. If want to actually succeed in adding a new a
    semiconductor device, my experience is it's easier to add it to 3f5
    than to xspice. There are so many related examples to choose
    from as a starting point. If you want to add some special
    function logic device, it would be easier *in principle* to
    add to xspice. But if you actually learn/know SPICE internals,
    then my direct experience again is that it's easier to add to
    spice3f5. After-all, you may quickly realize that your new
    special function requires a change in the overall SPICE
    integration algorithm. Anyway, I have actually been in that
    situation and choose that path. Now, years later, hindsight
    reinforces the soundness of that decision. I think you will
    find it easier to add new devices yourself to spice3 than to
    go through xspice's confining organization if you actually
    go through and succeed at the exercise.

    --Mike
     
  8. ...The fundamental reason, as I noted, there are 20+ c files to
    Kevin, you are a waste of time. This is one of the
    stupidest software engineering arguments I've ever seen.
    Each file only contains one function, most of which aren't
    needed. You can add all the functions in one file or even
    tack them in to some existing file so you can add a new
    device without added any files. Semiconductive models are
    typically added directly in a SPICE3 framework, e.g. BSIM3,
    SOI, EKV or VDMOS, not inside the xspice code model framework.

    SPICE uses a interesting combination of many different
    technologies including device physics, fantastically
    specialized numerical methods, various compiler
    technologies and general computer science as well
    as garden variety software engineering. It's no
    place for anyone who doesn't want to be interdisciplinarian.
    If a restrictive environment like xspice helps a pedestrian
    enter, that would be good. Maybe the original poster
    will be the first person to introduce a widely
    accepted new semiconductor model with xspice code models.

    But, I don't care how people add models to SPICE or who
    takes my advice or not. There's nothing in it for me.

    --Mike
     
  9. Steve Hamm

    Steve Hamm Guest

    By far the easiest way of doing this is to use a simulator that
    implements Verilog-A. Verilog-A allows expressing general
    differential-algebraic equations, so c(v) behavior (more properly,
    q(v) behavior) would be just i(br) <+ ddt(q);

    There's a bit of a movement toward coding _all_ spice models in
    Verilog-A, then letting a compiler handle generation of the code to
    interface to the simulator... Not a bad idea, really. There's enough
    to worry about in getting the physics right, without having to wonder
    about introducing bugs in plugging things into the simulator.
    Internal workings of spice: Nagel's dissertation and Quarles' notes on
    spice3. In looking at xspice, the code models seem a bit of a kluge;
    I've always wondered if they work well enough to model anything very
    complex.

    --Steve
     
  10. You mean you don't understand the point made.
    You missed the point completely. Sure, some of the files are not that
    involved, however, its the number of concepts in the files that matter.
    There's load this, add that, parse the other etc...XSpice code models
    are much cleaner.

    Semiconductive models are
    I know. I have done this myself. However, this does appear to highlight
    a decrepancy of one of your prior claims. Yo have stated in the past,
    that LTSpice is essentially a complete rewrite of the Spice code,
    containing maybe 5% of it. This seems a little odd as I assume you
    simple added in these external suites of, SOI, parker jfet files etc as
    is. How is it that a rewrite has the same basic architecture, even down
    to the same "doAnalysis" error messages?
    Yeah, right on. Next you'll be saying that only those potential
    Mozart's, and Brahms should be the ones allowed to take a music class.

    Your holy than thou pretentiousness crap, shown here, is again typical
    of your approach. What we have here is an individual who simple wants to
    do some work with a new model. He isn't trying to reinvent the theory of
    relativity. Spice isn't a closed club for the specially anointed. The
    reality is that most engineering is not done by "multidisciplinary"
    experts, nor is there any requirement that this be the case, or should
    be th case.

    Kevin Aylward

    http://www.anasoft.co.uk
    SuperSpice, a very affordable Mixed-Mode
    Windows Simulator with Schematic Capture,
    Waveform Display, FFT's and Filter Design.
     
  11. Chuck Harris

    Chuck Harris Guest

    Yeah, right on. Next you'll be saying that only those potential
    Not take a music class; but rather, would you like the results of a once
    in a blue moon musician tampering with a few measures of Beethoven's
    5th? Sure, he doesn't understand the whole work, but surely he can
    "improve" it by adding/changing a note or two here or there...
    Actually it is pretty much a closed club. The number if folks that can
    successfully create a useful model for ANY spice is very few. You can't
    do it unless you understand both spice, and the underlying physics of
    the device very well. You can tweek some "Beethoven's" model here and
    there and *perhaps* get a useful result, but to successfully make a new
    model out of "whole cloth" isn't likely. Your success has little to
    do with the internal mechanics of the spice you are modeling for; but
    alot to do with your interdisciplinary knowledge (of spice, software
    engineering, electronics, physics, etc.).

    That's why spice modelers get paid the big bucks by semiconductor
    manufacturers.


    -Chuck Harris
     
  12. I was not attacking you. It was you who made the personal comment
    "Kevin, you are a waste of time."

    What part of "next you'll be saying..." do you have trouble with?
    Any subject can be taken as "interdisciplinarian". Electronics design
    nessesarily requires English (or another language) to write a spec. I
    took the implication that you were inferring that one *requires*
    expertise in many subjects.
    Nonsense. Your opinion matters zilch. Again you have this habit of
    denying the actual facts of the case. XSpice is SPice3 with eXtensions.
    Spice3/XSpice is a well used and trusted spice platform used by hundreds
    of thousands of people.

    Once you actually get someone to pay for your product, you opinion on
    what constitutes a worthwhile product means nothing. I'm glad you have
    delusional comfort in how great your product is, despite the fact that,
    essentially, no one would use if it were not free.
    I don't recall anyone complaining that I Spam the NG.
    Indeed. I get many positive reports on my product.
    The you go again. One of your usual scientific, objective comments.
    Oh...so you must be one of those religious zealots who think sex is sex
    is disgusting, dirty, cheap, shouldn't be allowed except in the bedroom
    sort of fellow, despite the fact that all 6.3 Bilion of us are here
    because of it.
    Not at all. It doesn't matter what you say.
    Indeed, as do all competent businessmen.

    Kevin Aylward

    http://www.anasoft.co.uk
    SuperSpice, a very affordable Mixed-Mode
    Windows Simulator with Schematic Capture,
    Waveform Display, FFT's and Filter Design.
     
  13. : > Yeah, right on. Next you'll be saying that only those potential
    :> Mozart's, and Brahms should be the ones allowed to take a music class.

    : Not take a music class; but rather, would you like the results of a once
    : in a blue moon musician tampering with a few measures of Beethoven's
    : 5th? Sure, he doesn't understand the whole work, but surely he can
    : "improve" it by adding/changing a note or two here or there...

    :>
    :> Your holy than thou pretentiousness crap, shown here, is again typical
    :> of your approach. What we have here is an individual who simple wants to
    :> do some work with a new model. He isn't trying to reinvent the theory of
    :> relativity. Spice isn't a closed club for the specially anointed. The
    :> reality is that most engineering is not done by "multidisciplinary"
    :> experts, nor is there any requirement that this be the case, or should
    :> be th case.

    : Actually it is pretty much a closed club. The number if folks that can
    : successfully create a useful model for ANY spice is very few. You can't
    : do it unless you understand both spice, and the underlying physics of
    : the device very well. You can tweek some "Beethoven's" model here and
    : there and *perhaps* get a useful result, but to successfully make a new
    : model out of "whole cloth" isn't likely. Your success has little to
    : do with the internal mechanics of the spice you are modeling for; but
    : alot to do with your interdisciplinary knowledge (of spice, software
    : engineering, electronics, physics, etc.).

    I don't understand the point of your post, unless you just want to
    play the part of an overweening, elitist twit. I say: If you have to
    be Beethoven just in order to play the fiddle, then there will be no
    music anywhere.

    More to the point: if SPICE hacking were a closed club, only to be
    attempted by carefully groomed initiates, then analog simulation
    could not evolve and improve. Fortunately, you don't have to wear a
    secret SPICE decoder ring in order to understand enough physics &
    electronics to make improvements to SPICE. There are plenty of
    educated people out there who have the skills and interest to
    contribute. The multitude of different SPICE packages, commercial and
    freeware, demonstrates that. Yes, they may all come from the same
    root, but they are all now different, with different facilities built
    into them by different people to suit different purposes. That's
    progress.

    Moreover, XSpice was created with an explicit mechanism for extension,
    which allows people to create their own models. My initial post was
    a reasonable request to see if anybody had recommendations for books
    documenting that faculty (besides the XSpice manual). Nobody needs to
    wear a SPICE priesthood robe in order to extend the program using
    those hooks.

    : That's why spice modelers get paid the big bucks by semiconductor
    : manufacturers.

    I suspect that that's a thing of the past, and that many SPICE
    modelers are paid $30K/yr and live in India these days. The skills
    and knowledge are available to any intelligent person who takes the
    time to learn them, regardless of where they live, or whether they
    carry an "exclusive SPICE hacker's club" membership card.

    Stuart
     
  14. Jim Thompson

    Jim Thompson Guest

    Children! Could you take this private? Thanks!

    ...Jim Thompson
     
  15. Chuck Harris

    Chuck Harris Guest

    That you don't understand is quite clear from your post. My point is
    that if you don't take the time to learn a multidisciplinary collection
    of electrical engineering, physics, and software engineering skills,
    your efforts at modeling parts will be unlikely to result in anything
    useful.

    There is little that is less useful than a spice model that doesn't
    accurately represent the physical charecteristics of the part being
    modeled.
    The "club" isn't closed by any authority. It is one of those "clubs"
    where if you don't already know that you are capable of doing the job,
    you probably aren't. Life is full of "clubs" like that.
    To get into the "club" in India, you not only have to be very well
    educated, you also have to be in the correct socio-economic class.

    Their pay may suck, but India's programmers and engineers are equal
    to any found anywhere in the world. If you had worked with any of
    them, you would already know this.

    -Chuck
     
  16. : Stuart Brorson wrote:
    [ . . . . . bla bla bla . . . . .]

    : Their pay may suck, but India's programmers and engineers are equal
    : to any found anywhere in the world. If you had worked with any of
    : them, you would already know this.

    Well, I believe that this was my point -- that there are lots of
    intelligent, dilligent engineers all over the world who have the
    skills, interest, and knowledge to understand and contribute to SPICE
    & related programs. And I have indeed worked with plenty of them,
    doing both hardware & software, thank you very much.

    Your point seemes to be that you have to have a triple PhD in physics,
    circuits, and compilers, and belong to the elite SPICE club to get
    paid big bux for working on SPICE. This is elitest nonsense.
    Moreover, your arguments belie an attitude of sour clubbiness which
    don't contribute to your point.

    Thanks to everybody for their opinions about XSpice's merits and
    demerits. I'll bow out of this thread now.

    Stuart
     
  17. Only to you. You need to remove that bolder from your shoulder.
    Vigorously is hardly the way it was presented it. On the contrary, its
    you who are making the claim that any other method other than the Spice3
    route is crap.
    Err.. I suggested both methods were viable. I was the first to suggest
    that the poster copy and modify existing spice3 code. They both have
    their ups and down.
    Thats history for you. It sets precedents.
    Nope. The xspice connection port and parameters simplify a few of the
    concepts involved. Its a generalised method.

    It only takes about three functions,
    You dont say?
    Er... Its done all the time. Its called a rhetorical question. Look it
    up in an English book. Its actually quite common for those not locked up
    in their bedrooms typing on computers 23 hours a day.
    Rich? Delusions of granduer again. Leave it out mate. You don't half try
    and dress up Kirchoff's current and voltage laws.

    I've said this before, you should really reread you diatribe from the
    point of view of an uninterested party. oh, what was it now, LTSpice is
    of "historical proportions", or some similar such waffle.
    The *main* device equation is er.., in one file. What about all the
    other 100k+ lines of code that depends not one iota on the physics.
    There's vasts amounts of "effective" spice development that can be done
    without worrying about any physics at all.
    Compiler implementation familiarity? You don't say? Yeah. What sort of
    drugs are you on. Its add file, in MS VC++ and your done. I couldn't
    implement a compiler even if it resulted in 100 pints of Guinness, per
    week.

    Next you'll be saying the ability to type with 10 fingers is mandatory,
    which would put me in a bit of a predicament as I've only got 8, plus
    two thumbs.
    I am sure anyone knows that one can put 100k lines of code in one file
    if one so chooses. The point here is that if one is going to to add
    stuff either XSpice or Spice3 based, the sensible thing to do is use
    exactly the same format as the existing stuff. It makes it much easier
    to debug by comparison with what is known to work.
    There you go again. Your the only one in the known universe that
    knows/can how to write a spice program. Still full of it I see.
    Not at all. Love can't buy you money.
    Nope you don't. You have zero experimental evidence for that
    supposition. As they say, the only valid marketing survey is a signed
    purchase order.
    Yes, I know the types you deal with. Unfortunately, they aren't the
    100,000's who use free spices and that are perfectly willing to spend
    $5,000 for PSpice if they thought it was better.
    Oh dear... Oh dear... oh dear...You don't live in this real world do
    you.
    People can say what they like, but the proof is in the pudding.
    You believe this drivial don't you. Sad really, but if that whats makes
    you happy...
    That many?
    Yes, you do like to do this don't you.

    .. for a few parts per thousand of
    I agree, what with not looking a gift horse in the mouth, and giving
    away a usable Spice by a billion dollar company, could, in principle,
    wipe out the purchased Spice market.

    Kevin Aylward

    http://www.anasoft.co.uk
    SuperSpice, a very affordable Mixed-Mode
    Windows Simulator with Schematic Capture,
    Waveform Display, FFT's and Filter Design.
     
  18. *Anything* at all can be interpreted as "childishness" or "pointless" if
    phrased in such manner, so this means nothing.

    "why should some spend all day putting a little ball on a little twiggy
    thing and whack it about with sticks". "Why should some spend all day
    running about with big thingies on third shoulders, throwing misshapen
    balls about". "Why should some sit at a table, moving littlie blank and
    white things on little black and white squares etc...etc...

    So, there....Stick that in you pipe and smoke
    it....nah..nah..nah..nah..nah..nah..

    Kevin Aylward

    http://www.anasoft.co.uk
    SuperSpice, a very affordable Mixed-Mode
    Windows Simulator with Schematic Capture,
    Waveform Display, FFT's and Filter Design.
     
  19. Chuck Harris

    Chuck Harris Guest

    Then you have missed my point completely!


    -Chuck
     
  20. Active8

    Active8 Guest

    i sometimes look for Kevin/Mike exchanges in the thread view just to
    break the monotony :) this one wasn't very good. the flame level just
    wasn't there. they're slacking.

    but that brings up something i've been thinking of lately. considering
    that the PSpice documentation raises more questions than it answers...
    that the docs are nearly useless...

    i was thinking it may have been easier to just use SS and LTSpice for
    sims. you know, generate a netlist from SS where at least the capture
    part is a no brainer. at least creating parts should be easier than it
    is in LTSpice. drop the netlist in LTSpice and probe the output in SS.

    can you imagine the shit that could get started between those two when i
    start hammering them both with questions? :) ^2

    SS *and* LTSpice in the subject lines...

    i've saved as many of helmut's LTSpice answers as i came across, just in
    case. he's put out some good help for creating new parts. maybe Linear
    should put him on the payroll.

    brs,
    mike
     
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