Hacking a depletion MOSFET model

If you want to simulate a circuit with an LND150 at the typical 1.6 mA Idss, you could just add a resistor in the source. Seriously.

I also see a very consistent 1.6 mA for the LND150 and 250.

Nah, just another leftist moron, trying to shut you up by shouting "RACIST". ...just like they taught him on CNN.

Perhaps. What I'm having trouble understanding is how he can be so densely incorrect, yet argue that he's right... blatant ignorance I guess. ...Jim Thompson

It doesn't occur to Jim that he might be being blatantly ignorant - as he s o often is in areas outside of electronics. Somebody who is back on chemoth erapy may not have quite the grasp of the fine points of Spice modelling th at he has when he is in better health.

It doesn't quite occur to slowman that I am absolutely correct on this topic. (Though it actually does occur to slowman... he's just a pathological liar... or maybe he's just "pathological" >:-}

Tim, the youngster, is bloviating so much he's foaming at the mouth... but still doesn't know shit about Spice models...

"MJ" is used in the "model card" and has only to do with the junction CAPACITANCE grading.

"M" is used in the "instantiation" of a device (or subcircuit)... otherwise known as a LINE IN THE NETLIST for you amateurs.

(I posted what this "instantiation" should look like in...

Message-ID: )

Sorry if some of you prima donnas got your poor "fweeeelings" hurt... but you deserved it.

BTW: I still invite visitors, who are wanting to learn, to drop by... just give me a call (or E-mail) first to make sure I'm in town. ...Jim Thompson

Since when did "being correct"[*] interest the CNN-o-philes. One doesn't have to have any facts to shout someone down. It helps to be completely devoid of facts.

Krw has a complete set of "facts" - they were installed in his cranium some time ago, and he hasn't yet realised that his set isn't entirely correct (which is why CNN contradicts them from time to time) or remotely complete.

e so often is in areas outside of electronics. Somebody who is back on chem otherapy may not have quite the grasp of the fine points of Spice modelling that he has when he is in better health.

If that was supposed to be a link, it doesn't work - just keeps on asking m e if I'm a robot.

Phil Hobbs opened this thread with a request for help on getting an LTSpice model to give him the observed IDSS - 1.6mA - when LTSpice gave him 2.4mA.

You responded within 15 minutes with an answer that didn't solve his proble m, as he pointed out almost immediately. Your reaction was

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

What .ASY are you using for the LND150? "

which was both unnecessarily rude, and failed to explain what the .ASY was, and why it mattered.

None of this did anything to solve his problem, and when he finally did fin d the .ASY file, your reaction was to suggest that he move to an NMOS4 mode l (without telling him where he might get one for the LND150).

You've managed to reiterate that that you think that you are an expert on a ll things Spice, but still haven't managed to solve Phil's problem.

Your grasp of cooperative behaviour has never been great, but your failure to address the actual question asked does suggest that you have lost the pl ot, and are re-running the "I'm the dominant male here" script without actu ally thinking about the problem you might have solved if you hadn't spirall ed off into being anti-social.

Hi Phil, did you ever figure out which parameter to tweak in the LND150 model to get it to fit better?

TIA George H.

Hmm I reduced VTO from -2.0 to -1.5 and that seemed to work.

George H.

Is that expedient even physics based?

Nope, it wasn't that important so I just bailed. A 50% error isn't that unusual in board-level SPICE models. ;)

Cheers

Phil Hobbs

OK, does changing VTO seem reasonable? Looking at the spec sheet,

-2.0 looks right.

However fitting the I_D vs R_source graph on page 3... well ~-1.5 works much better.

I'm kinda caring about that factor of two. I'll have to measure them individually I guess.

George H.

You may find that all the devices in a batch are pretty close to each other. Let us know.

Everybody who has any LND150s or LND250s could measure Idss and post here. Sample different batches.

I vote 1.65 mA with 5 volts on the drain.

I'm wanting a 100uA current limit, so I'll measure and pick the G-S R.

George H.

Here's some stuff I have:

Thanks, 10 k ohm seems to give a nice 100 uA limit, but the spice model gave me 200 uA... And that is the max CW current of my spad, so I certainly want to stay away from that.

Speaking of my spad, I've been trying to make a model of it I can use in spice. I'm starting another thread.

George H.

Level=3 is the standard old text book model. Curve trace (curve tracers still exist don't they?) some devices and curve fit... trivial. ...Jim Thompson

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