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Old 3rd March 2014, 12:22 AM   #51
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Well, I was adjusting some quasi-saturation models for the BC3x7-40 and found a bug in the simulator model code! Sent it to Mike and he fixed it almost instantly. It's funny, there's programmers and then there's super-programmers like Mike. I'm really curious what makes the difference.

At any rate, the fixed quasi-sat update for LTSpice should be available tomorrow or the day after according to him. Changelog.txt in the LTSpice directory should indicate the fix after it's added.

This problem probably doesn't affect anyone here, because there are almost no general-purpose models that use the quasisat parameters anyway. My BC3x7-40 models will eventually.
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Old 3rd March 2014, 08:44 AM   #52
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Quote:
Originally Posted by keantoken View Post
Well, I was adjusting some quasi-saturation models for the BC3x7-40 and found a bug in the simulator model code! Sent it to Mike and he fixed it almost instantly. It's funny, there's programmers and then there's super-programmers like Mike. I'm really curious what makes the difference.
It does take a mind as well to identify such obscure hidden bugs. Not so easy.
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Old 3rd March 2014, 10:44 AM   #53
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I was taught that every user of software must be able to check the accuracy of the results before they begin to depend on those results.

Now that we are all users, this rule has largely been forgotten.
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regards Andrew T.
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Old 3rd March 2014, 11:21 AM   #54
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Originally Posted by AndrewT View Post
I was taught that every user of software must be able to check the accuracy of the results before they begin to depend on those results.

Now that we are all users, this rule has largely been forgotten.
You may be right, and we're all going for the easy way and fall into complacency.

However you have to consider that so many more people are getting into things they would never have gotten into before, so there is a greatly increasing number of people using that stuff, and most without all the knowledge. So it's good that in such a community, some are taking on the role of mentors for the others aspiring to learn. Some of us are very eager to learn much more, and the sharing helps a lot.

Rome wasn't built in one day and many have the opportunity to make progress in their knowledge, and some day make contributions in finding bugs like this.
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Old 4th March 2014, 05:53 AM   #55
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The update was released today. Now I can finally finish my models!
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Old 4th March 2014, 12:58 PM   #56
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I applied the update earlier today, and as I thought, one thing that happens, even if no update is requested for the models, is that whatever changes we've made to the standard library files are overwritten.

I wonder how we can manage to replace the standard libraries and avoid having them go away at every update.
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Old 4th March 2014, 03:40 PM   #57
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Make the whole /lib/cmp directory read-only? I did that on Linux and it crashed LTSpice, but it worked.
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Old 4th March 2014, 03:43 PM   #58
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I cleaned up NXP's BF862 model -- doesn't quite fit the frame width, thus the extra "+"

* BF862 SPICE MODEL MARCH 2007 NXP SEMICONDUCTORS
* ENVELOPE SOT23
* Adapted for generic spice programs 3-4-2014
.subckt BF862 1 2 3
Ld 1 4 1.1nH
Ls 3 6 1.25nH
Lg 2 5 0.78nH
Rg 5 7 0.535 Ohm
Cds 1 3 0.0001pF
Cgs 2 3 1.05pF
Cgd 1 2 0.201pF
Co 4 6 0.35092pF
J1 4 7 6 JBF862
*JBF862 model parameters:
.model JBF862 NJF(Beta=47.800E-3 Betatce=-.5 Rd=.8 Rs=7.5000 Lambda=37.300E-3
+ Vto=-.57093
+ Vtotc=-2.0000E-3 Is=424.60E-12 Isr=2.995p N=1 Nr=2 Xti=3 Alpha=-1.0000E-3
+ Vk=59.97 Cgd=7.4002E-12 M=.6015 Pb=.5 Fc=.5 Cgs=8.2890E-12 Kf=87.5E-18
+ Af=1)
.ends
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Old 4th March 2014, 04:20 PM   #59
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Great! Interesting to have an external gate resistance of 0.5R. Must be an extremely thin bonding wire?

Few of us simulate inductances to within a few nH so I think the model can be taken out of the subcircuit and put in the standard.jft for convenience. People doing RF simulations will know they need to use the subcircuit model. What do you think? Maybe add a /lib/sym/parasitic directory containing symbols connected to parasitic subcircuits? There are probably generic subcircuits for each transistor package type that would be useful.
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Old 4th March 2014, 04:39 PM   #60
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It's probably an implanted gate so the 0.535R represents the geometric mean of the resistance between the gate pin and each infinitesimally small ("dx") portion of the gate geometry. Right next to the pin the gate resistance is ~0, but at the maximally farthest point the gate resistance is >1R; 0.535R is a weighted average.
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