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SPICE gets it wrong

Started by Tim Williams May 7, 2017
On Tue, 09 May 2017 17:14:10 -0700, John Larkin
<jjlarkin@highland_snip_technology.com> wrote:

>On Tue, 09 May 2017 20:06:35 -0400, krw@notreal.com wrote: > >>On Tue, 09 May 2017 16:32:11 -0700, John Larkin >><jjlarkin@highland_snip_technology.com> wrote: >> >>>On Tue, 9 May 2017 14:27:59 -0700 (PDT), whit3rd <whit3rd@gmail.com> >>>wrote: >>> >>>>On Sunday, May 7, 2017 at 5:14:50 PM UTC-7, Tim Williams wrote: >>>> >>>>> https://www.seventransistorlabs.com/Images/BakerDarlington.png >>>>> >>>>> I discovered the oscillator on the left, when attempting to build a >>>>> Darlington transistor pair with a Baker clamp. >>>> >>>>> I think the TL;DR is: >>>>> 1. TIP31Cs suck as switching transistors to begin with, >>>>> 2. The TIP31C SPICE model sucks, despite them having half a century to try >>>>> and get it right. >>>> >>>>In the right application, TIP31 is quite a nice switch (it makes a good >>>>driver for a low-dropout regulator, for instance). Power transistors >>>>usually don't >>> >>>I rarely use bipolar transistors any more. >> >>They're cheap. > >A 2N7002 or FDV301 costs us 2 cents.
The threshold voltage of 7002s is horrible. Anything with a decent threshold voltage is more expensive than that and NPNs are less than a couple of cents anyway. A dual or a dual pre-biased saves a bunch in placement costs, too, though we can't use them as I/O.
> >MTP10N10 is 100 volts, 10 amps, TO220, 37 cents.
On an infinite heatsink?
On Tue, 09 May 2017 20:57:38 -0400, krw@notreal.com wrote:

>On Tue, 09 May 2017 17:14:10 -0700, John Larkin ><jjlarkin@highland_snip_technology.com> wrote: > >>On Tue, 09 May 2017 20:06:35 -0400, krw@notreal.com wrote: >> >>>On Tue, 09 May 2017 16:32:11 -0700, John Larkin >>><jjlarkin@highland_snip_technology.com> wrote: >>> >>>>On Tue, 9 May 2017 14:27:59 -0700 (PDT), whit3rd <whit3rd@gmail.com> >>>>wrote: >>>> >>>>>On Sunday, May 7, 2017 at 5:14:50 PM UTC-7, Tim Williams wrote: >>>>> >>>>>> https://www.seventransistorlabs.com/Images/BakerDarlington.png >>>>>> >>>>>> I discovered the oscillator on the left, when attempting to build a >>>>>> Darlington transistor pair with a Baker clamp. >>>>> >>>>>> I think the TL;DR is: >>>>>> 1. TIP31Cs suck as switching transistors to begin with, >>>>>> 2. The TIP31C SPICE model sucks, despite them having half a century to try >>>>>> and get it right. >>>>> >>>>>In the right application, TIP31 is quite a nice switch (it makes a good >>>>>driver for a low-dropout regulator, for instance). Power transistors >>>>>usually don't >>>> >>>>I rarely use bipolar transistors any more. >>> >>>They're cheap. >> >>A 2N7002 or FDV301 costs us 2 cents. > >The threshold voltage of 7002s is horrible. Anything with a decent >threshold voltage is more expensive than that and NPNs are less than a >couple of cents anyway. A dual or a dual pre-biased saves a bunch in >placement costs, too, though we can't use them as I/O.
The FDV301 is a low-threshold part. Also 2 cents. I have done some fun things with 2N7002s. This is 50 volts into 50 ohms in 1.8 ns, transformer isolated: https://dl.dropboxusercontent.com/u/53724080/Circuits/Fast_Stuff/HV_mosfet_pulse.jpg In this application, I couldn't find a modern mosfet that was any better than the ancient 2N7002.
>> >>MTP10N10 is 100 volts, 10 amps, TO220, 37 cents. > >On an infinite heatsink?
According to the data sheet, it can dissipate 75 watts. It can switch a kilowatt. Fast. It doesn't need a lot of base current either. -- John Larkin Highland Technology, Inc lunatic fringe electronics
On Sun, 7 May 2017 19:14:26 -0500, "Tim Williams"
<tiwill@seventransistorlabs.com> wrote:

[snip]

>2. The TIP31C SPICE model sucks, despite them having half a century to try >and get it right. > >Tim
You shouldn't have titled your subject as "SPICE gets it wrong". It should have been "Spice got it exactly right for the inadequate model that was presented". ...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. "It is not in doing what you like, but in liking what you do that is the secret of happiness." -James Barrie
On Tuesday, May 9, 2017 at 5:14:20 PM UTC-7, John Larkin wrote:

> >>On Tue, 9 May 2017 14:27:59 -0700 (PDT), whit3rd <whit3rd@gmail.com> > >>wrote: > > >>>In the right application, TIP31 is quite a nice switch (it makes a good > >>>driver for a low-dropout regulator, for instance). Power transistors > >>>usually don't
> >>I rarely use bipolar transistors any more.
> A 2N7002 or FDV301 costs us 2 cents.
And, it won't work in the low-voltage LDO negative regulator <https://www.digikey.com/schemeit/project/neg-regulator-low-dropout-TVGG5BO301S0/> nor lots of other places. Bipolars' Vbe is usefully low and predictable.
On a sunny day (Tue, 09 May 2017 16:32:11 -0700) it happened John Larkin
<jjlarkin@highland_snip_technology.com> wrote in
<qak4hc5lre1ohrf47f734bvk2qqvfl634b@4ax.com>:

>I rarely use bipolar transistors any more.
Maybe for high end stuff like you are making, but for many down to earth things they are very useful, bipolars are basically current amplifiers. MOSFETS voltage to current converters. Both have their field of application where they are best. And there are some nice RF ones too.
On a sunny day (Tue, 09 May 2017 19:40:10 -0700) it happened John Larkin
<jjlarkin@highlandtechnology.com> wrote in
<hqu4hc5mgugjdfiqu09pk7j621gq1k4f4u@4ax.com>:

>I have done some fun things with 2N7002s. This is 50 volts into 50 >ohms in 1.8 ns, transformer isolated: > >https://dl.dropboxusercontent.com/u/53724080/Circuits/Fast_Stuff/HV_mosfet_pulse.jpg
I exected a circuit diagram ;-( Anybody can draw that scope picture in gimp. :-)
On a sunny day (Tue, 09 May 2017 22:05:42 -0700) it happened Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in
<ep75hclm7p09qde73jco4n1umscjt2krh9@4ax.com>:

>On Sun, 7 May 2017 19:14:26 -0500, "Tim Williams" ><tiwill@seventransistorlabs.com> wrote: > >[snip] > >>2. The TIP31C SPICE model sucks, despite them having half a century to try >>and get it right. >> >>Tim > >You shouldn't have titled your subject as "SPICE gets it wrong". > >It should have been "Spice got it exactly right for the inadequate >model that was presented".
True 'math got it right' in Epicycles too: https://en.wikipedia.org/wiki/Deferent_and_epicycle
On Wed, 10 May 2017 08:09:28 GMT, Jan Panteltje
<pNa0nStpealmtje@yahoo.com> wrote:

>On a sunny day (Tue, 09 May 2017 19:40:10 -0700) it happened John Larkin ><jjlarkin@highlandtechnology.com> wrote in ><hqu4hc5mgugjdfiqu09pk7j621gq1k4f4u@4ax.com>: > >>I have done some fun things with 2N7002s. This is 50 volts into 50 >>ohms in 1.8 ns, transformer isolated: >> >>https://dl.dropboxusercontent.com/u/53724080/Circuits/Fast_Stuff/HV_mosfet_pulse.jpg > > >I exected a circuit diagram ;-(
Sorry, that's too valuable to give away. I will say: drive the gates hard and ignore the data sheets.
> >Anybody can draw that scope picture in gimp. > >:-)
You can buy it and shoot your own scope pix! We have a 100 volt version, using different fets. https://dl.dropboxusercontent.com/u/53724080/Circuits/Fast_Stuff/HV_100v_Pulse.jpg I'd like to go higher and faster, with GaN fets and fancier transformers, but I don't think there's a market. -- John Larkin Highland Technology, Inc lunatic fringe electronics
On Wed, 10 May 2017 00:07:59 -0700 (PDT), whit3rd <whit3rd@gmail.com>
wrote:

>On Tuesday, May 9, 2017 at 5:14:20 PM UTC-7, John Larkin wrote: > >> >>On Tue, 9 May 2017 14:27:59 -0700 (PDT), whit3rd <whit3rd@gmail.com> >> >>wrote: >> >> >>>In the right application, TIP31 is quite a nice switch (it makes a good >> >>>driver for a low-dropout regulator, for instance). Power transistors >> >>>usually don't > >> >>I rarely use bipolar transistors any more. > >> A 2N7002 or FDV301 costs us 2 cents. > >And, it won't work in the low-voltage LDO negative regulator > ><https://www.digikey.com/schemeit/project/neg-regulator-low-dropout-TVGG5BO301S0/> > >nor lots of other places. Bipolars' Vbe is usefully low and predictable.
If there is some gate supply voltage available, a mosfet LDO can drop millivolts. https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/TEM2_LDOs.pdf There are commercial p-fet based integrated LDOs too. -- John Larkin Highland Technology, Inc lunatic fringe electronics
On a sunny day (Wed, 10 May 2017 07:23:04 -0700) it happened John Larkin
<jjlarkin@highlandtechnology.com> wrote in
<eb86hcpe0norhvl2vm1jsuqsedmocfleps@4ax.com>:

>On Wed, 10 May 2017 08:09:28 GMT, Jan Panteltje ><pNa0nStpealmtje@yahoo.com> wrote: > >>On a sunny day (Tue, 09 May 2017 19:40:10 -0700) it happened John Larkin >><jjlarkin@highlandtechnology.com> wrote in >><hqu4hc5mgugjdfiqu09pk7j621gq1k4f4u@4ax.com>: >> >>>I have done some fun things with 2N7002s. This is 50 volts into 50 >>>ohms in 1.8 ns, transformer isolated: >>> >>>https://dl.dropboxusercontent.com/u/53724080/Circuits/Fast_Stuff/HV_mosfet_pulse.jpg >> >> >>I exected a circuit diagram ;-( > >Sorry, that's too valuable to give away. I will say: drive the gates >hard and ignore the data sheets.
Let me guess, you used an ethernet transformer...?
>>Anybody can draw that scope picture in gimp. >> >>:-) > >You can buy it and shoot your own scope pix!
I see the 2N7002 goes for 8 Euro cent. But I am sure your design adds a significant amount of added value :-)
>We have a 100 volt version, using different fets. > >https://dl.dropboxusercontent.com/u/53724080/Circuits/Fast_Stuff/HV_100v_Pulse.jpg
There is a little oscillation at the start of the pulse.
>I'd like to go higher and faster, with GaN fets and fancier >transformers, but I don't think there's a market.
Maybe some science field, was just reading CERN started a new linear accellerator: https://home.cern/about/updates/2017/05/brand-new-linear-accelerator-cern