I'm fooling aroud with a circuit in LTSpice, and the regular Gummel-Poon model isn't capturing base-emitter breakdown.
I've googled around a bit, and the VBIC mdeol does seem to offer this, and LT Spice will run the VBIC model, but I can't seem to find a repsoitory of VBIC models.
I'd be grateful if anybody could poitn me to a VBIC model of the 2N3906 or any similar gold-doped PNP saturating switch.
-- Bill Sloman, Nijmegen
Bill Sloman a écrit :
You probably won't find it.
I've been interested in such models, VBIC, MEXTRAM and such because the GP doesn't model some effects, but those seem to be used exclusively by foundries, and probably not all of them (but not being in the IC business, in don't know). You could do your device characterization but IIRC even this isn't simple since this requires some parameter extraction that are more related to the process than to directly the transistor.
But for such a simple addition that you require, why not just add a reverse biased diode and tweak it's parameters so that the direct current is insignificant? Or a Vsource and a diode?
That'll be way more simple.
BTW the 3904/3906 aren't gold doped.
-- Thanks, Fred.
Not only that, but I don't know of ANY successful gold-doped PNP's. Gold-doping is used in NPN's. There've been some half-assed attempts at Platinum-doping of PNP's.
I'm always pleased to note that I'm the highest standard for Slowman's disdain, but please don't feed the jerk. Let him die that most unpleasant of deaths... alone ;-)
...Jim Thompson
-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 |
"Fred Bartoli" schreef in bericht news:4a37ecd7$0$29484$ snipped-for-privacy@news.free.fr...
The Baxandall class-D oscillator "squegs" when you use a decent-sized inductor to limit the current flowing into the centre tap
This doesn't happen when you model the circuit in LTSpice, but in real life the problem seesm to sets in when the feed inductor gets big enough to over-shoot and force the switching transistors to work in inverted mode, not that any of stuff on the circuit that I've read says this explicitly.
I managed to dig out Gummel-Poon parameters that cover inverted operation of the 2N3906, but even after plugging them into the circuit model, it still doesn't squeg. I'm forced to speculate that avalanching the base-emitter junction may turn on the transistor in some inconveniently helpful way. I've futzed around a biit trying to make the switching transistors turn on in a useful way when reversed biased, but I'm not getting anywhere.
My hope was that the VBIC model might do better. The LTSpice help notes claim that you can get some - at least - of the VBIC parameters out of Gummel-Poon data, but I was hoping for a less labour-intensive solution.
The right answer is probably to build an example and probe the hell out of it, but I'm off to Australia on Friday, and won't have access to a soldering iron until I get back at the beginning of September.
I should have known that ... and I won't make that mistake again. Thanks.
-- Bill Sloman, Nijmegen
Have always thought that the 2n4258 was one, but I don't know for sure.
-- Thanks, Fred.
"Fred Bartoli" schreef in bericht news:4a38a3a5$0$22400$ snipped-for-privacy@news.free.fr...
The National Semiconductor Discrete Semiconductor Products databook from
1989 lists the 2N4258 as being made with process 65, a "overlay double diffused, gold doped, silicon epitaxial device".Nobody seems to make it any more, but Fairchild still list the 2N5771 which used the same process, and Farnell still stock it - at roughly $2 per part in small quantities which does suggest that at least one gold-doped PNP part was tolerably successful.
And if anyone has has a VBIC model for the 2N5771, I'd love to get a copy - strictly for private study.
-- Bill Sloman,
Google doesn't find 2N4258 and "gold doped".
Like I say I've not heard of gold doped PNP's. I know that the laterals (PNP's) that I used on various TTL PLL chips in the '60's had REALLY lousy beta due to the gold... like 1-3 :-(
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
Obama... Recklessness Cloaked in Righteousness
Jim knows a lot of things that don't happen to be so. The 2N5771 - which is made by Fairchild with National's PNP gold-doped process 65 - has minimum beta's from 35 to 50 over the specified current range, and a maximum of 120. Not great, but rather better than "really lousy".
He's also got silly ideas about Barak Obama, no doubt equally well founded on real-world facts.
-- Bill Sloman, Nijmegen
Just dug out the 1989 National Discrete databook.
2N4258, from process 65 which also gave 2N4208, 3640, 5771. Complementary to process 21 which gave 2N2369, 2369 and 2369.Their beta @ 10mA/1V are (were :-( min/typ/max
30/85/150 for the PNP 35/70/150 for the NPNSure not great, but not so lousy...
Of course these are vertical transistors and not lateral. Obviously, you've done way too much IC design :-)
BTW, AFAIK the 2N5771 was widely used in Tek equipments.
-- Thanks, Fred.
and
of
or
Does that data book _state_ that the PNP's are gold-doped?
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
Isn\'t the definition of "totalitarian" when the government owns
significant manufacturing; and controls the major media outlets?
and
of
or
Yup, clearly stated:
Process 65 is an overlay, double-diffused, gold doped, silicon epitaxial device. Complement to process 21. This device was designed for very high speed saturated switching at collector currents to 50mA
Then, Process 21 is an overlay, double-diffused, gold doped, silicon epitaxial device. Complement to process 65. This device was designed for very high speed saturated switching at collector currents of 10mA to 100mA
-- Thanks, Fred.
Gummel-Poon
and
of
or
Well! Guess I learn something every day ;-) I always thought gold-doping would kill a PNP.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
Isn\'t the definition of "totalitarian" when the government owns
significant manufacturing; and controls the major media outlets?
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.