Hacking a depletion MOSFET model

Just change "M" from 1 to 0.667 ...Jim Thompson

You could add a resistor in the source!

Tried adding

.model LND150_16 ako:LND150 M=0.667

But it puked.

Error on line 7624 : .model lnd150_16 nmos (level=3 rs=150.00 nsub=5.0e13 delta=0.1 kappa=1.o tpg=1 cgdo=2.1716e-12 rd=40.0 vto=-2.0 vmax=1.0e8 eta=0.1 nfs=6.6e10 tox=1.0e-7 ld=1.698e-9 uo=862.425 xj=6.4666e-7 theta=1.0e-5 cgso=5.09e-10 l=10.0e-6 w=600e-6) m=0.667 * Unrecognized parameter "m" -- ignored

Maybe that parameter isn't in the level 3 model?

Cheers

Phil Hobbs

I thought you were a Spice "expert" ?>:-}

What .ASY are you using for the LND150? ...Jim Thompson

Nope, it isn't that useful for board-level stuff, except for smallish all-d iscrete designs where the models are reasonable, so that's one trick this p articular pony prefers to delegate if possible. ;)

The part is just an NMOS, no subcircuit.

Cheers

Phil Hobbs

You might, once in a while, try being helpful without being snarky.

I Spice fairly big board-level designs. Helps me get all the loop dynamics right, and computes power dissipations, and makes pretty waveforms for manuals.

Sometimes I actually design with Spice. I have a new high-voltage pulse generator topology that evolved (random mutation and selection) by fiddling with Spice. Spice understood the circuit before I did.

I'm frying some inductors above 1 MHz pulse rate because LT Spice forgot to include skin effect. I also had a problem caused by Conservation of Energy, an unfortutate invention of some thoughtless physicists.

Why did you snip this line, "What .ASY are you using for the LND150?"

That's the "being helpful" part.

The "snarky part" is because Engelhardt (sp?) doesn't follow standard spice convention... I expect AD to fix that once he's gone. ...Jim Thompson

Repeating myself, "What .ASY are you using for the LND150?" ...Jim Thompson

-- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

Thinking outside the box... producing elegant solutions, by understanding what nature is hiding.

"It is not in doing what you like, but in liking what you do that is the secret of happiness." -James Barrie

Not recommended, RS is already 150. Which with RD and a little leftover MOSFETting, comes to nearly 200 ohms Rds(on).

Phil: change KAPPA, heh well for two reasons, one get rid of that one point _oh_ and make it a one point _zero_, who knows where that came from :) -- but more to the point, decrease it a bit, to reduce gain and current. Check it against the drain curves, and adjust VTO and W as well to get good agreement. Chances are, it's way off anyway, so you can stand to get a much better fit here. Bonus points: measure it yourself, including the subtreshold region (set by VTO and NFS, I think?), and get an even more accurate model (do share the results, if you would be so kind. :-) ).

Also, make sure to put L and W in the component instance, if the simulator isn't PSPICE-compatible.

Tim

Yes! That's the way to do it... TC's be damned, but that'll be OK, right ?>:-} ...Jim Thompson

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

What does grading coefficient have to do with it? Also, LTspice specific parameters, come on... (I don't see anyone else using that symbol. Most use MJ.)

Tim

Like this...

(NMOS4.asy) ...Jim Thompson

Dum-diddley-dum-dum.

MJ is a _model_ parameter; M is a scaling factor which covers all the model parameters at once.

See...

You must have a big mouth, you have your foot in it so much of the time >:-} ...Jim Thompson

-- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at

Thinking outside the box... producing elegant solutions, by understanding what nature is hiding.

"It is not in doing what you like, but in liking what you do that is the secret of happiness." -James Barrie

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

See...

Pot, kettle, color of skin you find offensive...

Tim

The bog-standard LTspiceXVII one, as follows.

Cheers

Phil Hobbs

========== Version 4 SymbolType CELL LINE Normal 48 48 48 96 LINE Normal 16 80 48 80 LINE Normal 40 48 48 48 LINE Normal 16 48 40 44 LINE Normal 16 48 40 52 LINE Normal 40 44 40 52 LINE Normal 16 8 16 24 LINE Normal 16 40 16 56 LINE Normal 16 72 16 88 LINE Normal 0 80 8 80 LINE Normal 8 16 8 80 LINE Normal 48 16 16 16 LINE Normal 48 0 48 16 WINDOW 0 56 32 Left 0 WINDOW 3 56 72 Left 0 SYMATTR Value NMOS SYMATTR Prefix MN SYMATTR Description N-Channel MOSFET transistor PIN 48 0 NONE 0 PINATTR PinName D PINATTR SpiceOrder 1 PIN 0 80 NONE 0 PINATTR PinName G PINATTR SpiceOrder 2 PIN 48 96 NONE 0 PINATTR PinName S PINATTR SpiceOrder 3

You persist in dum-diddley-dum-dum.

You apparently have no clue of the difference between _model_ parameters and scaling factors, as in the "call" of a device...

Nxxx d g s b ModelName L= W= AD,AS,PD,PS,etc= M=

Sheeesh!

I looked to see if there was a booklet, "LTspice for dummies", but found none... I guess the authors of that series must figure it's hopeless ;-)

(But the title should be "LTspice _is_ for dummies" anyway >:-}

I find no skin color offensive. I do, however, find belligerent idiots offensive.

...Jim Thompson

I see no way to parameterize that. Use NMOS4 as the basis of your new .ASY and go from there. ...Jim Thompson

Yeah, should have known better than to ask for input on a subject where there's such a weirdly large amount of ego involvement here. I'll try the Yahoo group.

Cheers

Phil Hobbs