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Spice Diode Modeling of Forward Overshoot & Reverse Recovery

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  Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-01-30 17:37 -0700
    Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-01-30 17:33 -0800
      Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-01-30 18:38 -0700
        Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-01-30 17:50 -0800
          Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-01-30 19:13 -0700
            Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Clifford Heath <no.spam@please.net> - 2017-01-31 14:11 +1100
              Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery John Larkin <jjlarkin@highlandtechnology.com> - 2017-01-30 19:32 -0800
                Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Clifford Heath <no.spam@please.net> - 2017-01-31 15:46 +1100
        Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery gray_wolf <g_wolf@nospam.com> - 2017-01-31 12:00 -0600
          Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery John Larkin <jjlarkin@highlandtechnology.com> - 2017-01-31 18:50 -0800
      Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-01-31 08:23 -0700
        Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-02-03 17:27 -0800
          Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery pcdhobbs@gmail.com - 2017-02-03 17:53 -0800
      Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-01 10:06 -0700
        Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery John Larkin <jjlarkin@highlandtechnology.com> - 2017-02-01 09:48 -0800
          Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-01 11:28 -0700
            Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Tom Gardner <spamjunk@blueyonder.co.uk> - 2017-02-01 18:59 +0000
            Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-02-01 11:02 -0800
              Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-01 12:07 -0700
                Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-02-01 11:15 -0800
                  Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-01 12:27 -0700
                    Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-02-01 14:45 -0800
                      Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-01 15:54 -0700
                        Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-02-01 15:37 -0800
                          Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Cursitor Doom <curd@notformail.com> - 2017-02-03 19:54 +0000
            Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-02-03 09:26 -0500
              Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Winfield Hill <hill@rowland.harvard.edu> - 2017-02-03 06:36 -0800
                Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-04 09:06 -0700
                  Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery John Larkin <jjlarkin@highlandtechnology.com> - 2017-02-04 09:30 -0800
              Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-03 08:09 -0700
                Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-02-03 11:08 -0500
                  Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-03 09:24 -0700
                    Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-02-03 11:33 -0500
                      Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-03 09:43 -0700
                        Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery pcdhobbs@gmail.com - 2017-02-03 08:55 -0800
                          Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Tom Gardner <spamjunk@blueyonder.co.uk> - 2017-02-03 17:05 +0000
                        Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Tom Gardner <spamjunk@blueyonder.co.uk> - 2017-02-03 16:57 +0000
                        Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Winfield Hill <hill@rowland.harvard.edu> - 2017-02-03 09:20 -0800
                          Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-03 10:58 -0700
                            Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-02-03 10:18 -0800
                              Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-03 11:28 -0700
                          Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-03 12:34 -0700
                  Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery bulegoge@columbus.rr.com - 2017-02-03 08:26 -0800
                    Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-02-03 11:34 -0500
                  Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-02-03 18:31 -0600
                    Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery pcdhobbs@gmail.com - 2017-02-03 17:26 -0800
                      Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-02-04 09:08 -0600
                        Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-04 08:28 -0700
                        Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-02-04 12:33 -0500
                          Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery John Larkin <jjlarkin@highlandtechnology.com> - 2017-02-04 10:23 -0800
                            Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-02-04 13:50 -0500
                          Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-02-04 14:03 -0600
                            Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Clifford Heath <no.spam@please.net> - 2017-02-05 08:26 +1100
                        Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-04 11:14 -0700
                          Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Winfield Hill <hill@rowland.harvard.edu> - 2017-02-04 10:31 -0800
                            Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery John Larkin <jjlarkin@highlandtechnology.com> - 2017-02-04 11:20 -0800
                              Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Winfield Hill <hill@rowland.harvard.edu> - 2017-02-04 11:38 -0800
                                Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-04 12:54 -0700
                          Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-04 11:32 -0700
                        Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-05 09:07 -0700
                          Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery bill.sloman@ieee.org - 2017-02-05 19:01 -0800
                            Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-06 10:16 -0700
                              Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-06 15:01 -0700
                      Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery John Larkin <jjlarkin@highlandtechnology.com> - 2017-02-04 08:07 -0800
                        Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-02-04 12:38 -0500
                          Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery John Larkin <jjlarkin@highlandtechnology.com> - 2017-02-04 10:23 -0800
                    Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-03 19:08 -0700
                      Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery pcdhobbs@gmail.com - 2017-02-03 18:24 -0800
                        Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-03 20:10 -0700
                          Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-02-04 01:50 -0500
                            Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-04 08:26 -0700
                              Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Winfield Hill <hill@rowland.harvard.edu> - 2017-02-04 07:42 -0800
                                Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-04 09:02 -0700
                                Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-04 09:41 -0700
                                  Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery John Larkin <jjlarkin@highlandtechnology.com> - 2017-02-04 09:43 -0800
                              Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery bill.sloman@ieee.org - 2017-02-04 16:42 -0800
                          Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery John Larkin <jjlarkin@highlandtechnology.com> - 2017-02-04 08:08 -0800
                        Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery George Herold <gherold@teachspin.com> - 2017-02-04 10:27 -0800
                          Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery George Herold <gherold@teachspin.com> - 2017-02-04 10:34 -0800
                    Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-04 15:44 -0700
                      Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery pcdhobbs@gmail.com - 2017-02-04 16:29 -0800
                        Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-04 17:32 -0700
                          Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery John Larkin <jjlarkin@highlandtechnology.com> - 2017-02-04 18:58 -0800
          Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery JM <dontreplytothis173@gmail.com> - 2017-02-01 19:14 +0000
            Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-01 12:20 -0700
              Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery JM <dontreplytothis173@gmail.com> - 2017-02-01 19:36 +0000
                Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery JM <dontreplytothis173@gmail.com> - 2017-02-01 19:45 +0000
                Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-01 12:45 -0700
              Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery John Larkin <jjlarkin@highlandtechnology.com> - 2017-02-04 09:44 -0800
    Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Tim Wescott <tim@seemywebsite.com> - 2017-01-30 20:32 -0600
      Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-01-30 19:44 -0700
      Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery John Larkin <jjlarkin@highlandtechnology.com> - 2017-01-30 19:46 -0800
    Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-01 11:57 -0700
      Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-02-01 11:03 -0800
        Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-01 12:07 -0700
          Re: Spice Diode Modeling of Forward Overshoot & Reverse Recovery John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-02-01 11:10 -0800

Page 4 of 5 — ← Prev page 1 2 3 [4] 5  Next page →

#446370

On Monday, February 6, 2017 at 3:07:19 AM UTC+11, Jim Thompson wrote:
> On Sat, 4 Feb 2017 09:08:44 -0600, "Tim Williams"
> <tiwill@seventransistorlabs.com> wrote:

[snip]

> It struck me that most of the lurkers on this group are engineers.
> 
> All that an engineer cares about in regard to a Spice model is that
> it's terminal behavior be the same as the real device behaves in his
> system/PCB.
> 
> The engineer doesn't give a damn whether the model duplicates the
> actual physics of the device or not, only that it performs properly.
> 
> I would argue that attempting to model a device following the complete
> physics of a device produces a cumbersome, difficult to converge and
> slow-to-simulate model.

Not necessarily.

> I have 55 "learned"/peer-reviewed papers in my
> forward-overshoot/reverse-recovery research file that demonstrate my
> point ;-)
> 
> I would point out, for instance, that the Spice model for a bipolar
> device is not a model that conveys the actual physics of the device,
> but a simulatablely-tractable approximation.

Gummel-Poon doesn't capture inverted transistor behaviour that makes Baxandall class-D oscillators "squeg" when built with bipolar transistors and a too-big feed inductor.
 
> The elitists amongst us would insist that a proper model can't be
> created unless it "solves" the underlying physics equations.
> 
> That is nonsense.

It is. A proper model must respect the underlying physics as much as it can - and the underlying physics is often a royal route to a good model - but - as the Gummel-Poon example makes clear - an imperfect model can often be very useful.

It's nice if it's imperfections are spelled out, as they rarely are.
 
> In my musing, not even committed to paper yet, just rolling the
> function around in my head, I realized that a controlled charge
> accumulation, metered release could easily model the sacred SRD... no
> solution of a transport equation involved.

Phil Hobbs did spell out why this might not work as well as you like to think, and might have given you a clue to an approach that might work better.
 
> When I posted the waveforms of my forward recovery model, the resident
> pompous asshole reared his ugly head and pronounced, "...only
> waveforms".

Waveforms are the integrated output of complex processes. A waveform has one value at one moment. The process that generates the waveform has several variables all of which are varying with time.

> Sonnuva gun, I do believe that's what engineers want to see on their
> simulator and their 'scope... not a scrolling useless paper extolling
> that the physics equation has been solved.

That's what they want to see. This doesn't mean that it's what they ought to be looking for.
 
> Lastly, I think many people here are using LTspice, and the elitists
> and the resident pompous asshole hang their hats on the results...

We all know that LTSpice outputs can be misleading. The trick is to know when, where and why.
 
> I would suggest you check out the accuracy of the resident Spice
> models... all based on nearly ideal approximations to emphasize
> simulation speed... not accuracy.

Gummell-Poon is pretty accurate, where it works.  VBIC - which LTSpice will run - is supposed to be better, if you can get the parameters for a specific part. Semiconductor manufacturers treat them as trade secrets.

-- 
Bill Sloman, Sydney

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#446428

On Sun, 5 Feb 2017 19:01:04 -0800 (PST), bill.sloman@ieee.org wrote:

>On Monday, February 6, 2017 at 3:07:19 AM UTC+11, Jim Thompson wrote:

[snip]
> 
>> I would suggest you check out the accuracy of the resident Spice
>> models... all based on nearly ideal approximations to emphasize
>> simulation speed... not accuracy.
>
>Gummell-Poon is pretty accurate, where it works.  VBIC - which LTSpice will run - is supposed to be better, if you can get the parameters for a specific part. Semiconductor manufacturers treat them as trade secrets.

Most of the foundries I deal with (that have processes with bipolar
devices) _do_ provide VBIC models (PSpice runs them as well).

Unfortunately most _discrete_ device manufacturers don't provide
adequate models, if they provide any at all.
		
                                        ...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 http://www.analog-innovations.com |    1962     |

     Thinking outside the box... producing elegant solutions.

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#446477

On Mon, 06 Feb 2017 10:16:43 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>On Sun, 5 Feb 2017 19:01:04 -0800 (PST), bill.sloman@ieee.org wrote:
>
>>On Monday, February 6, 2017 at 3:07:19 AM UTC+11, Jim Thompson wrote:
>
>[snip]
>> 
>>> I would suggest you check out the accuracy of the resident Spice
>>> models... all based on nearly ideal approximations to emphasize
>>> simulation speed... not accuracy.
>>
>>Gummell-Poon is pretty accurate, where it works.  VBIC - which LTSpice will run - is supposed to be better, if you can get the parameters for a specific part. Semiconductor manufacturers treat them as trade secrets.
>
>Most of the foundries I deal with (that have processes with bipolar
>devices) _do_ provide VBIC models (PSpice runs them as well).
>
>Unfortunately most _discrete_ device manufacturers don't provide
>adequate models, if they provide any at all.
>		
>                                        ...Jim Thompson

You missed that my point was about LTspice... LTspice's default models
are gross simplifications.
		
                                        ...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 http://www.analog-innovations.com |    1962     |

     Thinking outside the box... producing elegant solutions.

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#446099

On Fri, 3 Feb 2017 17:26:34 -0800 (PST), pcdhobbs@gmail.com wrote:

>>Phil, 
>
>>Do you have any example data that illustrates the necessity of solving the 
>>transport equation exactly? 
>
>>Tim 
>
>Well, JL's Grekhov diode pulser is a good one, as are normal SRDs. Even the lowly 1N914 will get charge density waves set up in it if you hit it with a fast ringy pulse, and the details of the response will depend on carrier diffusion.

A model for the Grehkov effect would only be useful if one were
designing the doping profile on purpose. But the DSRS application is
obscure and it's more practical to just test available power diodes,
of unknown guts, for behavior. The best Grehkov diode that I've found
was the c-b junction of a power transistor, based on no more theory
than a vague hunch.


-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics 

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#446114

On 02/04/2017 11:07 AM, John Larkin wrote:
> On Fri, 3 Feb 2017 17:26:34 -0800 (PST), pcdhobbs@gmail.com wrote:
>
>>> Phil,
>>
>>> Do you have any example data that illustrates the necessity of
>>> solving the transport equation exactly?
>>
>>> Tim
>>
>> Well, JL's Grekhov diode pulser is a good one, as are normal SRDs.
>> Even the lowly 1N914 will get charge density waves set up in it if
>> you hit it with a fast ringy pulse, and the details of the response
>> will depend on carrier diffusion.

>
> A model for the Grehkov effect would only be useful if one were
> designing the doping profile on purpose. But the DSRS application is
> obscure and it's more practical to just test available power diodes,
> of unknown guts, for behavior. The best Grehkov diode that I've
> found was the c-b junction of a power transistor, based on no more
> theory than a vague hunch.

Sure, one doesn't do that sort of thing for no reason.  The
photodetection example I gave upthread is maybe more apropos--you really 
do want to use that to guide the design of the photodiode.

I have a device from Excelitas whose propagation delay varies no more 
than 30 ps over the full width of the active area.  Some C-V 
measurements showed that it has an APD-style structure inside, i.e. a 
buried layer of high doping that generates a huge electric field when 
you deplete it fully.  Bolting a transport capability onto SPICE would 
allow optimizing that and trading it off against capacitance and series 
resistance, and seeing what the whole circuit would do.  I'd give my eye 
teeth to be able to do that.

Cheers

Phil Hobbs


-- 
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

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#446124

On Sat, 4 Feb 2017 12:38:56 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>On 02/04/2017 11:07 AM, John Larkin wrote:
>> On Fri, 3 Feb 2017 17:26:34 -0800 (PST), pcdhobbs@gmail.com wrote:
>>
>>>> Phil,
>>>
>>>> Do you have any example data that illustrates the necessity of
>>>> solving the transport equation exactly?
>>>
>>>> Tim
>>>
>>> Well, JL's Grekhov diode pulser is a good one, as are normal SRDs.
>>> Even the lowly 1N914 will get charge density waves set up in it if
>>> you hit it with a fast ringy pulse, and the details of the response
>>> will depend on carrier diffusion.
>
>>
>> A model for the Grehkov effect would only be useful if one were
>> designing the doping profile on purpose. But the DSRS application is
>> obscure and it's more practical to just test available power diodes,
>> of unknown guts, for behavior. The best Grehkov diode that I've
>> found was the c-b junction of a power transistor, based on no more
>> theory than a vague hunch.
>
>Sure, one doesn't do that sort of thing for no reason.  The
>photodetection example I gave upthread is maybe more apropos--you really 
>do want to use that to guide the design of the photodiode.

Actually, the hunch was guided by the observation that diffused
non-epitaxial junctions have a better chance of blundering into a good
doping profile. Boff discovered the step-recovery effect like that,
lucky diffusion profile. Theorists then followed up and optimized it.

Epitaxial junctions don't seem to snap.

>
>I have a device from Excelitas whose propagation delay varies no more 
>than 30 ps over the full width of the active area.  Some C-V 
>measurements showed that it has an APD-style structure inside, i.e. a 
>buried layer of high doping that generates a huge electric field when 
>you deplete it fully.  Bolting a transport capability onto SPICE would 
>allow optimizing that and trading it off against capacitance and series 
>resistance, and seeing what the whole circuit would do.  I'd give my eye 
>teeth to be able to do that.
>
>Cheers
>
>Phil Hobbs

The PD case would involve inputting 3D doping profiles and anode
metalization patterns and such, hardly Spice stuff. I guess that,
knowing all that, you could do a better Spice model. Do you think that
Spice model would benefit from some sort of diffusion element, hacked
like the transmission line? I just kluge up something that behaves
like the real thing over a narrow operating range.




-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics 

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#446043

On Fri, 3 Feb 2017 18:31:16 -0600, "Tim Williams"
<tiwill@seventransistorlabs.com> wrote:

>"Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message 
>news:yb2dna0H3qF7NwnFnZ2dnUU7-V3NnZ2d@supernews.com...
>> And since it doesn't model actual diffusion behaviour, I have no reason to 
>> suppose that it would work in more complicated and realistic situations 
>> such as tone bursts in wideband noise.
>
>Phil,
>
>Do you have any example data that illustrates the necessity of solving the 
>transport equation exactly?
>
>Tim

Particularly given the ability, in Spice, of creating a
voltage-and-current-and-charge variable capacitor ?>:-}

Then Spice can solve the so-called "transport equation".
		
                                        ...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 http://www.analog-innovations.com |    1962     |

     Thinking outside the box... producing elegant solutions.

[toc] | [prev] | [next] | [standalone]

#446046

>Particularly given the ability, in Spice, of creating a 
>voltage-and-current-and-charge variable capacitor ?>:-} 

>Then Spice can solve the so-called "transport equation". 

I thought you didn't want to talk about it any more. 

But you're entirely wrong once again. Any sort of capacitor--nonlinear, time varying, whatever you like--still obeys an ODE. Transport doesn't. 

Cheers

Phil Hobbs

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#446047

On Fri, 3 Feb 2017 18:24:38 -0800 (PST), pcdhobbs@gmail.com wrote:

>>Particularly given the ability, in Spice, of creating a 
>>voltage-and-current-and-charge variable capacitor ?>:-} 
>
>>Then Spice can solve the so-called "transport equation". 
>
>I thought you didn't want to talk about it any more. 
>
>But you're entirely wrong once again. Any sort of capacitor--nonlinear, time varying, whatever you like--still obeys an ODE. Transport doesn't. 
>
>Cheers
>
>Phil Hobbs
>

Please explain _why_ you think Spice can't solve it.  Stop thinking
explicit solutions... Spice is a numeric machine.
		
                                        ...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 http://www.analog-innovations.com |    1962     |

     Thinking outside the box... producing elegant solutions.

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#446059

On 02/03/2017 10:10 PM, Jim Thompson wrote:

>>> Particularly given the ability, in Spice, of creating a
>>> voltage-and-current-and-charge variable capacitor ?>:-}
>>
>>> Then Spice can solve the so-called "transport equation".
>>
>> I thought you didn't want to talk about it any more.
>>
>> But you're entirely wrong once again. Any sort of
>> capacitor--nonlinear, time varying, whatever you like--still obeys
>> an ODE. Transport doesn't.

> Please explain _why_ you think Spice can't solve it.  Stop thinking
> explicit solutions... Spice is a numeric machine.

A particular kind of numeric machine, but not a universal one, however
clever a modeller you may be.

SPICE is a pretty capable solver for sparse systems of nonlinear,
coupled, ordinary differential equations, and suffices for most circuit
purposes as well as a large class of other problems that can be reduced
to such a system.

A general system of N variables leads to an NxN matrix that has to be
solved on each time step. The effort required goes as N**3, which gets
old fast.

Sparse systems have many fewer nonzero elements, typically just a few
near the main diagonal.  For instance, FDTD codes such as my EM
simulator lead to a heptadiagonal matrix (seven entries per row,
corresponding to the current volume element and six nearest neighbours.
That kind is pretty simple to solve, in theory, taking a few times N 
operations per time step.  (FDTD is a bit slower because you have to 
shrink the time step as you refine the mesh, so it goes like N**(4/3).)

However, circuits aren't that regular, leading to sparse systems whose
nonzero entries can be anywhere, but which typically have no more than
five or so connections per node, which helps a lot.

Like all (or nearly all) solvers for systems like that, SPICE uses
iterative methods that take more steps but avoid filling in the zero
entries. These methods aren't guaranteed to converge unless the system
is numerically stable and the initial guess is sufficiently close, which
is why SPICE needs all that help with convergence.

It's a good tool all round, but it can only solve ODE systems unless the 
code is hacked up to add features (such as transmission lines).

Transport problems such as gas motion are not in general expressible as
systems of ODEs. Classical nonequilibrium gas transport is governed by 
the Boltzmann equation (see e.g. 
<https://en.wikipedia.org/wiki/Boltzmann_equation>) which is an 
irreducible integrodifferential equation.

Carrier motion is more complicated because there are two kinds of 
carriers that move and recombine according to quantum rules, and because 
electric and magnetic fields are coupled to the phase space density, but 
it's still a set of coupled integrodifferential equations, and so can't 
be solved by SPICE.

The difference is basically that integrodifferential equations have a 
lot of internal state that ODEs don't, and they can be nonlocal in time, 
i.e. the result of the next step doesn't depend merely on the 
observables from the previous step.

For instance, a transmission line in SPICE is also an integral equation, 
because what comes out one end is a delayed replica of what went in the 
other end.  You can't express that as a differential equation, because 
it has internal state that isn't visible at the terminals.  You have to 
express it as a convolution integral with a shifted Dirac delta function 
(perhaps with a high frequency cutoff).

ODE systems have a very rich set of possible responses, so (as you know 
better than I) it's possible to dream up ways to mimic the behaviour of 
many IDEs with SPICE models in restricted situations.  For instance, if 
you know that the transmission line will only have pulses going into it, 
you can use a delayed source to mimic that.

However, because these models don't correctly represent the internal 
state of the solutions of the transport equation, a change in conditions 
is very likely to make the mimicry fail.  Sending charge density waves 
into a 1N914 by hitting it with a step with a big 2-GHz ring is an 
example.  A model based only on the response to a clean step is unlikely 
to get that right, because it has no way of expressing the wave 
behaviour, which will have excursions in both density and momentum.

Transmission lines are sufficiently important that it's worth hacking up 
the solver to handle them as a special case, which fortunately is quite 
simple.  Transport is another kettle of fish entirely.

Cheers

Phil Hobbs

-- 
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

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#446089

On Sat, 4 Feb 2017 01:50:22 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

[snip]
>
>However, because these models don't correctly represent the internal 
>state of the solutions of the transport equation, a change in conditions 
>is very likely to make the mimicry fail.  Sending charge density waves 
>into a 1N914 by hitting it with a step with a big 2-GHz ring is an 
>example.  A model based only on the response to a clean step is unlikely 
>to get that right, because it has no way of expressing the wave 
>behaviour, which will have excursions in both density and momentum.
>
[snip]

What does the real device do under such circumstances?

Win's post, while at a much lower frequency, would indicate nothing
visible.

Besides, forward overshoot and reverse recovery are of most importance
to the power supply application, not something with a "2-GHz ring".

I have 55 "learned" papers on Spice modeling forward overshoot and
reverse recovery.

Their models are grotesque complex because they aren't Spice
aficionados, they're equation bangers ;-)

However their models do match the measured behavior quite closely.

But so does mine at 11 lines total... a much simpler approach using
controlled sources (that allow equations in their templates ;-)

I _will_ ultimately publish.  What I seek yet is a way to simply plug
in numbers from a datasheet and automatically parameterize the model's
equations.  Right now I have to manually twiddle coefficients until I
get a fit.

Of note, once fit, the model behavior _does_ track slew rate _and_
peak current values.
		
                                        ...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 http://www.analog-innovations.com |    1962     |

     Thinking outside the box... producing elegant solutions.

[toc] | [prev] | [next] | [standalone]

#446093

Jim Thompson wrote...
>
> Win's post, while at a much lower frequency,
> would indicate nothing visible.

 My post?  Do you mean John's scope traces post?


-- 
 Thanks,
    - Win

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#446096

On 4 Feb 2017 07:42:56 -0800, Winfield Hill <hill@rowland.harvard.edu>
wrote:

>Jim Thompson wrote...
>>
>> Win's post, while at a much lower frequency,
>> would indicate nothing visible.
>
> My post?  Do you mean John's scope traces post?

I guess you didn't post it, but someone posted a link to your
experiment forward biasing a 1N914 at various rates.

I'll see if I can re-find that link.
		
                                        ...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 http://www.analog-innovations.com |    1962     |

     Thinking outside the box... producing elegant solutions.

[toc] | [prev] | [next] | [standalone]

#446106

On 4 Feb 2017 07:42:56 -0800, Winfield Hill <hill@rowland.harvard.edu>
wrote:

>Jim Thompson wrote...
>>
>> Win's post, while at a much lower frequency,
>> would indicate nothing visible.
>
> My post?  Do you mean John's scope traces post?

My error, it was an experiment by Pease, not by you...

<https://www.dropbox.com/s/6s0o7j2rx59k5i8/pease.pdf?dl=0>
		
                                        ...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 http://www.analog-innovations.com |    1962     |

     Thinking outside the box... producing elegant solutions.

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#446116

On Sat, 04 Feb 2017 09:41:48 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>On 4 Feb 2017 07:42:56 -0800, Winfield Hill <hill@rowland.harvard.edu>
>wrote:
>
>>Jim Thompson wrote...
>>>
>>> Win's post, while at a much lower frequency,
>>> would indicate nothing visible.
>>
>> My post?  Do you mean John's scope traces post?
>
>My error, it was an experiment by Pease, not by you...
>
><https://www.dropbox.com/s/6s0o7j2rx59k5i8/pease.pdf?dl=0>
>		
>                                        ...Jim Thompson

At 1 mA, the rise is slow and capacitances dominate, so he didn't get
much overshoot. Slam it harder, and you can forward-bias a 1N914 to
lots of volts. Pease's observed change of overshoot with rep rate
suggests some very slow diffusions going on.

https://dl.dropboxusercontent.com/u/53724080/Parts/Diode_TurnOn/1N914_c.JPG

I've run power diodes at 48 volts forward bias, for a while.

We used (or, actually, couldn't use) some laser diodes that acted like
they had big inductors or something inside. A sneak-up-on-it drive
pulse would create a big voltage overshoot and a long wait for light
to come out. If it was pulsed at maybe 1 MHz, the effect disappeared.
One of the layers was acting like a slow PIN diode in series with the
rest.



-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics 

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#446195

On Sunday, February 5, 2017 at 2:27:10 AM UTC+11, Jim Thompson wrote:
> On Sat, 4 Feb 2017 01:50:22 -0500, Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
> 
> [snip]
> >
> >However, because these models don't correctly represent the internal 
> >state of the solutions of the transport equation, a change in conditions 
> >is very likely to make the mimicry fail.  Sending charge density waves 
> >into a 1N914 by hitting it with a step with a big 2-GHz ring is an 
> >example.  A model based only on the response to a clean step is unlikely 
> >to get that right, because it has no way of expressing the wave 
> >behaviour, which will have excursions in both density and momentum.
> >
> [snip]
> 
> What does the real device do under such circumstances?
> 
> Win's post, while at a much lower frequency, would indicate nothing
> visible.
> 
> Besides, forward overshoot and reverse recovery are of most importance
> to the power supply application, not something with a "2-GHz ring".
> 
> I have 55 "learned" papers on Spice modeling forward overshoot and
> reverse recovery.
> 
> Their models are grotesque complex because they aren't Spice
> aficionados, they're equation bangers ;-)
> 
> However their models do match the measured behavior quite closely.
> 
> But so does mine at 11 lines total... a much simpler approach using
> controlled sources (that allow equations in their templates ;-)
> 
> I _will_ ultimately publish.  What I seek yet is a way to simply plug
> in numbers from a datasheet and automatically parameterize the model's
> equations.  Right now I have to manually twiddle coefficients until I
> get a fit.\

Sounds like a job for a nonlinear multi-parameter least squares curve fitting procedure.

My Ph.D. project used Fletcher-Powell - the Fortran package solution available from the computation department was based on Marquardt but couldn't be shoe-horned into my software, so I had to write my own, and the Fletcher-Powell approach seemed more suitable for my particular problem.

https://en.wikipedia.org/wiki/Davidon%E2%80%93Fletcher%E2%80%93Powell_formula

https://en.wikipedia.org/wiki/Non-linear_least_squares
 
> Of note, once fit, the model behavior _does_ track slew rate _and_
> peak current values.

Working within a restricted parameter space, a model doesn't have to be physically realistic to work. Physically realistic models can be  expected to hold up better when used outside the operating range within which the model was fitted.

-- 
Bill Sloman, Sydney

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#446100

On Fri, 03 Feb 2017 20:10:37 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>On Fri, 3 Feb 2017 18:24:38 -0800 (PST), pcdhobbs@gmail.com wrote:
>
>>>Particularly given the ability, in Spice, of creating a 
>>>voltage-and-current-and-charge variable capacitor ?>:-} 
>>
>>>Then Spice can solve the so-called "transport equation". 
>>
>>I thought you didn't want to talk about it any more. 
>>
>>But you're entirely wrong once again. Any sort of capacitor--nonlinear, time varying, whatever you like--still obeys an ODE. Transport doesn't. 
>>
>>Cheers
>>
>>Phil Hobbs
>>
>
>Please explain _why_ you think Spice can't solve it.  Stop thinking
>explicit solutions... Spice is a numeric machine.
>		
>  

                                      ...Jim Thompson



And what happened to "end of discussion" ?


-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics 

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#446127

On Friday, February 3, 2017 at 9:24:41 PM UTC-5, pcdh...@gmail.com wrote:
> >Particularly given the ability, in Spice, of creating a 
> >voltage-and-current-and-charge variable capacitor ?>:-} 
> 
> >Then Spice can solve the so-called "transport equation". 
> 
> I thought you didn't want to talk about it any more. 
> 
> But you're entirely wrong once again. Any sort of capacitor--nonlinear, time varying, whatever you like--still obeys an ODE. Transport doesn't. 
> 
> Cheers
> 
> Phil Hobbs

Phil, (I feel like I'm barley touching bottom math-wise, so be gentle.) 
But can't you sorta solve transport equations by putting in initial 
conditions, turn the differentials into differences and then step
the solution along, with a small enough time step.  ?
George H.  

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#446131

On Saturday, February 4, 2017 at 1:27:31 PM UTC-5, George Herold wrote:
> On Friday, February 3, 2017 at 9:24:41 PM UTC-5, pcdh...@gmail.com wrote:
> > >Particularly given the ability, in Spice, of creating a 
> > >voltage-and-current-and-charge variable capacitor ?>:-} 
> > 
> > >Then Spice can solve the so-called "transport equation". 
> > 
> > I thought you didn't want to talk about it any more. 
> > 
> > But you're entirely wrong once again. Any sort of capacitor--nonlinear, time varying, whatever you like--still obeys an ODE. Transport doesn't. 
> > 
> > Cheers
> > 
> > Phil Hobbs
> 
> Phil, (I feel like I'm barley touching bottom math-wise, so be gentle.) 
> But can't you sorta solve transport equations by putting in initial 
> conditions, turn the differentials into differences and then step
> the solution along, with a small enough time step.  ?
> George H.

Oops Phil, just ignore that... I hadn't gotten to your latter 
reply to JT.

Geo

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#446172

On Fri, 3 Feb 2017 18:31:16 -0600, "Tim Williams"
<tiwill@seventransistorlabs.com> wrote:

>"Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message 
>news:yb2dna0H3qF7NwnFnZ2dnUU7-V3NnZ2d@supernews.com...
>> And since it doesn't model actual diffusion behaviour, I have no reason to 
>> suppose that it would work in more complicated and realistic situations 
>> such as tone bursts in wideband noise.
>
>Phil,
>
>Do you have any example data that illustrates the necessity of solving the 
>transport equation exactly?
>
>Tim

I have retrieved a few SRD papers.

Looks like I can even model "transport" in Spice.

Nothing is impossible to model with Spice.

Watch this space >:-}
		
                                        ...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 http://www.analog-innovations.com |    1962     |

     Thinking outside the box... producing elegant solutions.

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