2N7000 Spice Model

The 2N7000/2N7002 parts themselves vary a lot between manufacturers, which is why some of our products specify a specific manufacturer for these parts.

What non-physical behavior are you seeing?

I would hope to see some electrical behaviour!

I really don't understand the confusion here. The number 2N7000 is a JEDEC registered number, how can there be a variance at all ?

I admit I have very little experience with Spice, but JEDEC is JEDEC, no ?

Going into this "given samples" s*it is one thing, but should not be an iss ue in design usually. Tolerances are one thing. Current sharing amond MOSFE Ts is another, but I doubt anyone has to match a 2N7000 for that purpose.

In fact I would like to see the scenario in which that would be necessary. Well not really in practice, what I mean is for one of the seasoned enginee rs around here to actually explain why the $^%#@ #$$&* you owuld have to do that. I thought the thing was a simple switcher, maybe use it linear somet imes, but only if you bought a truckload of them. At least that's what I th ink.

Typical behaviors could be radically better than the Jedec requirements. Some 2N7002s are ten times as fast as you'd expect from the max rise/fall time specs. Gate leakages can be 8 or so orders of magnitude below the specs.

I suspect that one fabbed wafer gets sold as a lot of different part numbers. Nobody really needs 7000+ different transistors.

All but the Supertex model failed to model ANY behavior below threshold, and the Supertex model had discontinuities in the ID/VDS curve blending... guaranteed to cause simulator convergence issues. ...Jim Thompson

I forgot to reference my old post (4/6/2005)...

Second page tells it all. ...Jim Thompson

Fairchild FQD2N100 model attached.

If you're actually designing boards with 2N7000s, any of those curves is about as good as any other. Real-life parts will be all over the map.

You didn't notice the discontinuities? ...Jim Thompson

Sure, but they are down in the "noise" of part-part differences.

So let me get this straight. If any little thing happens this is smoked, right ?

Refer back in the history of this group, and Win Hill's concern about operation in the subthreshold region. Use as a low noise amplifier is quite different from just using the device as a switch. ...Jim Thompson

Here's a graph that I found in our PDATA folder for the 2N7000. I don't know where it came from, possibly from Win.

(people should sign and date everything that they create)

What does "subthreshold" mean anyhow? It seeme to me that specified gate thresholds are based on arbitrary drain currents. That curve above has no threshold.

No model level higher then Level=3... that is, early school-boy text-book complexity.

The problem is that it is quite rare to see discrete MOS devices modeled properly as BSIM3v3. ...Jim Thompson

That's not "leakage", it's the natural square-law behavior of MOS devices below "threshold"... sometimes used to make faux bandgaps with MOS ;-)

I suspect Joerg regularly works down in this region.

I recently participated in the design of a medical device (chip) where _everything_ operated subthreshold... the oscillators I mentioned before... 1kHz at 6nA, 1MHz at 1.2uA

The definition of "threshold" is a vague. I have these papers that I can share, if any are interested...

...\ModelingIssues\ThresholdModeling_SalcedoEtAl.pdf

...\MOS-GateCharge\WinHill_subthreshold_mosfet_model.pdf (graphs)

...\MOS-GateCharge\Win Hill Data\2n7000_data_graphs.xls (data)

...\SubthresholdEffects\CurrentMirror_Novel_SubthresholdRegion.pdf

...\SubthresholdEffects\ExploitingSubthresholdMOSFET_Behavior.pdf

...\SubthresholdEffects\ReferencesFromSubthreshold MOSFETs.pdf

...\SubthresholdEffects\SubthresholdDeviceModeling.pdf

...\SubthresholdEffects\SubthresholdMOSforUltra-LowPower.pdf ...Jim Thompson

Very pretty. What was V_GS?

Cheers

Phil Hobbs

Not if the board function depends on sub-threshold behavior!

Do you mean Vds? I don't know.

V_DS, right. Ah, well, I'll have to quit snuggling with my computer and actually do some measurements. ;)

Cheers

Phil Hobbs