In the ltspice diode models there are a number of variable which can be set Vpk, Ipk, Iave etc which "allow LTspice to check if the diode is being used beyond its rated capability". If you run a simulation is there an easy way to tell if one of the components has exceeded its rating without examining each component individual?
any help appreciated
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Hi all,
Anybody has a working file for typical 2180 VCA? I don't need a very accurate model, just one that gives me basic operation.
Thanks
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Interesting idea.. Thanks .. Will try it out..
"It drops to 12 ppm when I replace the capacitor with a 10K resistor. A
pure resistor divider should give better accuracy than that.."
The fact that a pure resistive network, produces these errors suggest
that the errors are due to the spice algorithm used to interpolate for
the zero crossings All interpolation algorithms will converge to the
right answer, when the time step is very small ,approaching zero....
Instead of interpolating, a neighborhood search around the "Measure
points" may produce an effective answer. Normally we ask the question,
"What voltage at a given time?" The question that needs to be asked i "
what time for a given voltage?".
I think multiplying to a lower frequency will ease the time step burden;
but it will not alter the interpolation issue..
And there is the additional multiplication errors..
Remember that I am not even using my circuit yet.. I am simply
measuring LTspice's sine wave generator put through a resistive divider..
cheers
AG
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Show quoted text
On 9/21/2011 5:43 AM, Kendall Castor-Perry wrote:
Funnily enough I used LTSpice to model a delta-sigma synthesizer a while
back. A 1.6Mpoint FFT was quite good at giving what appeared to be both
precise and accurate answers That's where I discovered that video
acceleration slows down screen plotting, which could take five minutes
to do
a redraw... The simulation stopped working with one of the updates, and I
never revisited it.
But anyway in your particular case, why not use stick a generator of known
frequency on the simulation, and plot the product of that and your own
output, cleaned up with an RC or other simple filter? In other words, just
mix down to a lower IF for display purposes. That'll improve the
'countability' of zero crossings. You'll still need a pretty short
timestep
if you want the accuracy, though. / Kendall
|
Funnily enough I used LTSpice to model a delta-sigma synthesizer a while
back. A 1.6Mpoint FFT was quite good at giving what appeared to be both
precise and accurate answers That's where I discovered that video
acceleration slows down screen plotting, which could take five minutes to do
a redraw... The simulation stopped working with one of the updates, and I
never revisited it.
But anyway in your particular case, why not use stick a generator of known
frequency on the simulation, and plot the product of that and your own
output, cleaned up with an RC or other simple filter? In other words, just
mix down to a lower IF for display purposes. That'll improve the
'countability' of zero crossings. You'll still need a pretty short timestep
if you want the accuracy, though. / Kendall
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Half Bridge IRF7317 or Si4500BDY
Do you know if these half bridges are available somewhere? Thanks
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Re: Monte Carlo beta and temp on 2N3904
--- In LTspice@..., Analog Hack <analoghack@...> wrote:
Hello,
I have, what may be, a dumb question.? I have been attempting to Monte Carlo some of the BJT parameters on the 2N3904, NPN transistor.? Some of the directives I have tried include (as an example of the bf parameter):
.model 2N3904 NPN(bf=300)
.param bf={mc(300, tol)}
.param tol=0.5
.step param x 1 100 1
and so on.
Other parameters I would be interested in mc'ing are: Vaf, Var, Rb, Xtb and Trb1.? I have been having no luck and was wondering if it is even possible to do an mc on the parameters of a standard bjt library compopnent.? Do I need to make my own sub circuit?
Please let me know.? Thanks AH
[Non-text portions of this message have been removed]
Hello AH. You have successfully generated a Monte Carlo variable bf, but you don't reference it in your .model statement - bf is fixed at 300. Normally, curly braces are involved with parameters that are varied at run time, like this: .model 2N3904 NPN(bf={bf}) A a search of the Files section will reveal more information and several working examples. This should always be the first place you look for examples - there is a staggering number there. You might note, there is also an example supplied in the \Examples directory of the LTspice installation. It has also been discussed many times here - you could also check the message archive. Note, in your example, LTspice will complain about multiple instances of the same model, since the 2N3904 is already in standard.bjt. Using a different name is a good idea. Regards, Tony
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Re: Regarding Delay Element simulation
Thanks a lot for your suggestion andy.
I have tried and simulated the same and got the results too..
I couldn't figure out ,what those output waveforms trying to say?Actually it is a delay element, it is supposed to give delayed o/p.But i couldn't understand any delayed verion of outputs.
I have uploaded the same results in folder Files -> Temp -> "Diff-amp-based delay element_simulated output.JPG".
Can you see and reply me, what that delay element o/p exactly trying to say..
Please do the needful.
Dinesh
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Show quoted text
--- In LTspice@..., Andy <Andrew.Ingraham@...> wrote:
Other than that, all are fine??please confirm.. Well, try it and see!
shall i give clock signal for the nodes VIN_P, VIN_N, and VBIAS_P?? You can give whatever signals you want to, to those nodes. It is your
circuit to simulate. Just don't leave them floating or LTspice will
complain.
My guess is that VBIAS_P should probably be a DC voltage, and then
VIN_P and VIN_N would be some sort of differential signal or
common-mode signal or some combination of the two. Whether it is a
single pulse or a clock signal or a semi-random data signal, is
entirely up to you and what you want to simulate.
If you don't know what signals to use, please ask your co-worker or
your teacher what to do.
Andy
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Re: New Member and Updated Help File
On Sep 20, 2011, at 4:40 PM, Tim wrote: This just in from Mike:
"I'd rather not. I don't supply the information
for the Wiki site, so it's really better if I don't
endorse it. "
Tim
--- In LTspice@..., "Tim" <thutches@...> wrote:
With that encouragement, I sent the idea on to Mike.
So we'll see...
Tim
--- In LTspice@..., wagnerj@ wrote:
Maybe it would "help the Help" if Mike would put a direct link
to the Wiki
page in the LTspice Help tab. So there would be three items in
the that
tab, "Help", "Wiki" and "About". That would remind everyone,
new and old,
that there is more Help than they think --
Tim I second that. Its much more than a reminder. The whole idea of
help is to
be able to find answers to questions when you need answers. If
you have to
fumble around for a link to a wiki, then you have lost time and
increased
frustration levels. Further, if you don't use the wiki very
often, it is
easy to forget where you have stashed the link.
Having a link in that spot would be a great service to users.
Jim Wagner
Oregon Research Electronics
Then it ought to go in the Help FAQ were the Yahoo group is listed. Jim Wagner [Non-text portions of this message have been removed]
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Re: New Member and Updated Help File
This just in from Mike:
"I'd rather not.? I don't supply the information
for the Wiki site, so it's really better if I don't
endorse it. "
Tim
toggle quoted message
Show quoted text
--- In LTspice@..., "Tim" <thutches@...> wrote:
With that encouragement, I sent the idea on to Mike.
So we'll see...
Tim
--- In LTspice@..., wagnerj@ wrote:
Maybe it would "help the Help" if Mike would put a direct link to the Wiki
page in the LTspice Help tab. So there would be three items in the that
tab, "Help", "Wiki" and "About". That would remind everyone, new and old,
that there is more Help than they think --
Tim I second that. Its much more than a reminder. The whole idea of help is to
be able to find answers to questions when you need answers. If you have to
fumble around for a link to a wiki, then you have lost time and increased
frustration levels. Further, if you don't use the wiki very often, it is
easy to forget where you have stashed the link.
Having a link in that spot would be a great service to users.
Jim Wagner
Oregon Research Electronics
|
Monte Carlo beta and temp on 2N3904
Hello,
I have, what may be, a dumb question.? I have been attempting to Monte Carlo some of the BJT parameters on the 2N3904, NPN transistor.? Some of the directives I have tried include (as an example of the bf parameter):
.model 2N3904 NPN(bf=300)
.param bf={mc(300, tol)}
.param tol=0.5
.step param x 1 100 1
and so on.
Other parameters I would be interested in mc'ing are: Vaf, Var, Rb, Xtb and Trb1.? I have been having no luck and was wondering if it is even possible to do an mc on the parameters of a standard bjt library compopnent.? Do I need to make my own sub circuit?
Please let me know.? Thanks AH
[Non-text portions of this message have been removed]
|
Re: New Member and Updated Help File
With that encouragement, I sent the idea on to Mike.
So we'll see...
Tim
toggle quoted message
Show quoted text
--- In LTspice@..., wagnerj@... wrote:
Maybe it would "help the Help" if Mike would put a direct link to the Wiki
page in the LTspice Help tab. So there would be three items in the that
tab, "Help", "Wiki" and "About". That would remind everyone, new and old,
that there is more Help than they think --
Tim I second that. Its much more than a reminder. The whole idea of help is to
be able to find answers to questions when you need answers. If you have to
fumble around for a link to a wiki, then you have lost time and increased
frustration levels. Further, if you don't use the wiki very often, it is
easy to forget where you have stashed the link.
Having a link in that spot would be a great service to users.
Jim Wagner
Oregon Research Electronics
|
Re: New Member and Updated Help File
Maybe it would "help the Help" if Mike would put a direct link to the Wiki
page in the LTspice Help tab. So there would be three items in the that
tab, "Help", "Wiki" and "About". That would remind everyone, new and old,
that there is more Help than they think --
Tim I second that. Its much more than a reminder. The whole idea of help is to be able to find answers to questions when you need answers. If you have to fumble around for a link to a wiki, then you have lost time and increased frustration levels. Further, if you don't use the wiki very often, it is easy to forget where you have stashed the link. Having a link in that spot would be a great service to users. Jim Wagner Oregon Research Electronics
|
Re: New Member and Updated Help File
Maybe it would "help the Help" if Mike would put a direct link to the Wiki page in the LTspice Help tab. So there would be three items in the that tab, "Help", "Wiki" and "About". That would remind everyone, new and old, that there is more Help than they think --
Tim
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Show quoted text
--- In LTspice@..., "Tony Casey" <tony@...> wrote:
<snip>
--- In LTspice@..., "Lewis" <lineblp@> wrote:
Here's an update on using the provided help from LTspice as a basis for
an expanded and annotated help in LTwiki <> :
- Mike graciously allowed use of the existing help as a basis for an
expanded and annotated help in LTwiki, specifically the LTspiceHelp.chm
not the scad3.pdf.
- In doing so, we must make it clear what is the original versus the
annotated.
- I've succeeded in converting the Help to an HTML series of files.
This conversion can be seen at:
LTspice Help <>
-I'm now working on my test server LTwiki to (more or less) seamlessly
incorporate this help as a stub for a section titled 'Annotated and
Expanded LTspice Help'. The approach I'm trying is Iframe Widgets into
the MediaWiki engine that you know of as LTwiki.org
- The end result is to have this Help on the wiki, but the annotating
authors would then further explain, illustrate and annotate a given stub
as they see fit.
best regards,
Lewis
</snip>
Hello Lewis,
Sounds like you're making good progress.
I seem to remember that Iframes used to be viewed suspiciously by web security products and experts, and were sometimes blocked. I presume that's not an issue now, or may be it never was?
Would you envisage the expanded help to be able to form a stand alone document that can be browsed without being online? It's possible it would be most useful if it could be used, at least initially, as an alternative to the standard help, for those people that don't or can't get on with the regular one; although I realise this would be much more problematic regarding rights, permission and good will, particularly since you have already obtained permission for it to be used on the Wiki.
Getting people - and I suppose I mean new users, generally - to use the help at all is hard enough, but the more "helps" there are, the less likely they will be to use any of them, I fear.
Do you have any statistics on how many people actually visit the Wiki?
Regards,
Tony
|
The data sheet at
will let you fix up similar transistors for which there may be a LTspice
model..
An email to the apps people in STmicro might get it to you faster...
cheers
AG
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On 9/20/2011 4:06 PM, bhorste wrote:
I've been doing some poking around here and on the Web, and I can't
find many models for power BJTs. Specifically I'm looking for a
BUL128, but I'll take as many as I can get at this point. I'm working
on designing a capacitor multiplier power supply. Thanks.
-Ben
|
Re: New Member and Updated Help File
<snip> --- In LTspice@..., "Lewis" <lineblp@...> wrote:
Here's an update on using the provided help from LTspice as a basis for
an expanded and annotated help in LTwiki <> :
- Mike graciously allowed use of the existing help as a basis for an
expanded and annotated help in LTwiki, specifically the LTspiceHelp.chm
not the scad3.pdf.
- In doing so, we must make it clear what is the original versus the
annotated.
- I've succeeded in converting the Help to an HTML series of files.
This conversion can be seen at:
LTspice Help <>
-I'm now working on my test server LTwiki to (more or less) seamlessly
incorporate this help as a stub for a section titled 'Annotated and
Expanded LTspice Help'. The approach I'm trying is Iframe Widgets into
the MediaWiki engine that you know of as LTwiki.org
- The end result is to have this Help on the wiki, but the annotating
authors would then further explain, illustrate and annotate a given stub
as they see fit.
best regards,
Lewis
</snip> Hello Lewis, Sounds like you're making good progress. I seem to remember that Iframes used to be viewed suspiciously by web security products and experts, and were sometimes blocked. I presume that's not an issue now, or may be it never was? Would you envisage the expanded help to be able to form a stand alone document that can be browsed without being online? It's possible it would be most useful if it could be used, at least initially, as an alternative to the standard help, for those people that don't or can't get on with the regular one; although I realise this would be much more problematic regarding rights, permission and good will, particularly since you have already obtained permission for it to be used on the Wiki. Getting people - and I suppose I mean new users, generally - to use the help at all is hard enough, but the more "helps" there are, the less likely they will be to use any of them, I fear. Do you have any statistics on how many people actually visit the Wiki? Regards, Tony
|
I've been doing some poking around here and on the Web, and I can't find many models for power BJTs. Specifically I'm looking for a BUL128, but I'll take as many as I can get at this point. I'm working on designing a capacitor multiplier power supply. Thanks.
-Ben
|
The more I read what you say, the more convinced I am that a software
delta-sigma may improve the accuracy( assuming numdgts will fix the
precision).
Cheers
AG
--------------------------------------------------------------------------------------------
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On 9/20/2011 3:09 PM, Tony Casey wrote:
<snip>
--- In LTspice@... <mailto:LTspice%40yahoogroups.com>,
Ganesan <dg1@...> wrote:
Thanks ..Explains the RC case but not the RRcase.. Further 1ppm of 10k
is 100psec. My real frequency in more complex circuits are 100s of
megahertz.. That puts the steps size in the 10 femptoseconds.. Yikes...
There must be a better way..
</snip>
I think it explains everything once you consider that SPICE's
automatic timestep algorithm is not exposed to the user, unless you
override it.
Perhaps you can see why I questioned your use of SPICE in this
context. The "better way" is to accept that SPICE is the wrong tool
for this job.
Regards,
tony
|
Thanks
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On 9/20/2011 3:00 PM, John Woodgate wrote:
In message <4E78EC92.4080505@...
<mailto:4E78EC92.4080505%40austin.rr.com>>, dated Tue, 20 Sep 2011,
Ganesan <dg1@... <mailto:dg1%40austin.rr.com>> writes:
femptoseconds Please remove the p.
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<snip> --- In LTspice@..., Ganesan <dg1@...> wrote:
Thanks ..Explains the RC case but not the RRcase.. Further 1ppm of 10k
is 100psec. My real frequency in more complex circuits are 100s of
megahertz.. That puts the steps size in the 10 femptoseconds.. Yikes...
There must be a better way..
</snip> I think it explains everything once you consider that SPICE's automatic timestep algorithm is not exposed to the user, unless you override it. Perhaps you can see why I questioned your use of SPICE in this context. The "better way" is to accept that SPICE is the wrong tool for this job. Regards, tony
|
I think measuring the period over a thousand cycles and running it
through a software delta- sigma might be a better choice.. I just dont
know how to implement this in LTspice parlance..
Cheers
AG
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Show quoted text
On 9/20/2011 2:47 PM, Ganesan wrote:
I tried the numdgt=15. As I suspected it improves the "Precision", but
not the "accuracy"
cheers
AG
On 9/20/2011 2:42 PM, Ganesan wrote:
Thanks ..Explains the RC case but not the RRcase.. Further 1ppm of 10k
is 100psec. My real frequency in more complex circuits are 100s of
megahertz.. That puts the steps size in the 10 femptoseconds.. Yikes...
There must be a better way..
On 9/20/2011 2:13 PM, Tony Casey wrote:
<snip>
--- In LTspice@... <mailto:LTspice%40yahoogroups.com>
<mailto:LTspice%40yahoogroups.com>
<mailto:LTspice%40yahoogroups.com>,
Ganesan <dg1@...> wrote:
I uploaded the file
File-> Temp ->RC_meas_freq.asc
<>
I applied your recommended technique.
I get an accuracy of 40 ppm.. I am afraid the result may be worse in
very complex circuits with non-linear caps..
I would like to get an accuracy of 0.1ppm to 1ppm (Xtal
oscillators and
time references).
" How do you measure frequency of an oscillator accurately?"
cheers
AG </snip>
Hello AG,
The first thing you can do is try all the usual things that improve
accuracy:
1. Add a minimum timestep (I realise you have a philosophical
objection to this). Adding a minimum step of 10n completely fixes your
measurement issue in this case - 0ppm error.
2. When necessary, you can invoke double precision data storage by
adding .option numdgt 15. Read the .option section of the Help.
3. Add a redundant slave B source with the tripdt and tripdv clauses.
these can often be more efficient than a minimum timestep.
I suspect trying to accurately count the frequency of high stability
sources in SPICE might be a complete waste of time, although that
might depend exactly what you mean by high stability. It is in
principle possible to model a Caesium standard with SPICE, although
with stabilities of the order of 1E-14, the required simulation time
might be weeks or months. Just a thought.
Regards,
Tony
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thutches