The LT Spice "g" componant is a voltage dependant current source. The relationship could be your equation, or a polynomial, or anything. That would be *one* line of text. Add capacitance or ESL as needed.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Yep. The MOV equation is one line of GVALUE... with coefficients set by VTEST, ITEST, VCLAMP, ICLAMP, Rseries, Lseries and Cpar, right from the data sheet.
But apparently too difficult for Larkin the psychopathic asshole to master plugging in the numbers. ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
One line? What line? This one maybe?
1e0b22458c9e013c316e1a17d2fb21f94017955ce88f51ef5c03aab498e88eb5e71f71e1875841719b8947fe3d6f920cb7af1fedfab169c9c17d1a3c4a3fa116-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
You will NEVER see the equation, as simple as it is, NEVER >:-} ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Oh no, no, I'm heartbroken.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Good >:-} ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...
"Document ID" says it's an "ISpice Model", but extension says it's a .DWG.... WTF?
Of course, an IC is something quite a bit more involved than a passive two-terminal. It would take time, especially if no good resources are available. I wouldn't do that for free (nor would I guess you, either!).
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
That link is certainly an AutoCAD Drawing (.DWG)
A typical I/C (or hybrid, as I've been doing lately) usually takes me
3-6 weeks.There _is_ an ISpice model of the NCP1072 rummaging around, but it apparently won't run on anything but ISpice. I haven't tried to decipher its syntax into Berkeley-compliant... yet. ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
I've seen that advertised before in appnotes, but it doesn't make sense. There's no physical reason to have a power law in a semiconducting device, and it suggests way more leakage current than there should be (the breakdown region might be softer than an exponential, but there still has to be an exponential leakage tail in there). Perhaps it's just a crude fit to the random breakdown-ESR pattern. In much the same way as 1/f noise (another odd order power law) can be modeled as a stacked chain of noise sources of random bandwidth.
SPICE won't appreciate it, because a negative number to a random power is likely to result in some random complex number. You'd at least need abs(V) to start, then put the sign back on the current later. Most of the derivatives all disappear at V=0, which doesn't help.
A symmetrical exponential function, like tanh, would probably do a good job, though being a bit too sharp. As John says, connecting some resistors in series with that, then cleaning it up with a few more of different threshold voltages and ESRs, would do; but some may balk at this solution using "too many lines". :)
A single-line rendering of that isn't actually possible, because a "resistor in series with an exponential" is a transcendental equation, and has to be solved iteratively by the SPICE engine. Your alternative would be to build a "dulled" tanh function (say, toning down the exponential asymptotes by taking the sqrt or something), but that is also impossible, because the only thing that's "dull" enough to tame an exponential is a log (any polynomial or power law just becomes a constant factor to the exponent). But that simply undoes the exponent entirely, giving flat asymptotes; and doesn't work for negative values (see
Probably, best would be to sit down with a spreadsheet and plug in curves until it works. There's always boring old polynomials, which are probably quite a good idea in this case -- with the right combination of (complex) poles and zeroes, the function can be odd (= gives opposite current for negative argument) and the asymptotes can be linear or quadratic (linear would make sense in that it's the minimum ESR when all semiconducting grains are conducting). With some tweaking, perhaps a non-geometric polynomial could be built that exhibits realistic leakage current, and approximates the V^alpha asymptote.
One can also make polynomials from other polynomials (Chebyshev and other named orthogonal polynomial series are typically better for building curve-fits than just throwing coefficients at a geometric series), or from other functions (e.g., the periodic polynomials in cos^n(phi) and such, useful for harmonic analysis).
Tim
-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
I can't say whether it makes physical sense, but in the limited research I've done into the characteristics of metal oxide varistors, the I = k* V^alpha equation keeps popping up. In the curve matching that I have done (in Excel, mind you), a bit of series resistance kept the curve from flattening out too much at high applied voltages, and also made sense in terms of the bulk resistance of the material (disregarding the grain boundaries where all the non-linear magic occurs).
Definitely, it would need a bit of a wrapper around it (sign() and abs() functions) to make it symmetrical. I tend to post from my phone, so tenseness is rewarded (at least while I'm typing).
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