Re: Freqeucny Dependent resistor
I believe it is impossible to have a physically realizable resistor that is frequency dependent and has no reactive component. A transmission line comes close in that its resistance is almost constant for a range of frequencies, but as you know at very low frequencies, neglecting any series resistive components, its reactance is largely capacitive.
Hubert
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----- Original Message -----
From: Tony Casey
To: LTspice@...
Sent: Thursday, September 15, 2011 12:43 PM
Subject: [LTspice] Re: Freqeucny Dependent resistor
<snip>
--- In LTspice@..., Christian Thomas <ct.waveform@...> wrote:
>
> Well, that's a question AG.
>
> Might we not be looking at a naive question here? Ie. Can I please have a
> resistor that changes with frequency but with none of those nasty reactive
> elements? If that's the case then looking in the s-plane is not the answer
> being sought.
>
> In which case the answer needed is "No, you can't. Or at least you can't
> have a full solution. (I think that must be right). But we do have some
> useful reactive components that perform that function, and that's what
> everyone else uses. C and L in LTSpice; and their s-plane behaviour is
> built in."
>
> CT
</snip>
Hello Christian,
I'm sure you ask the question tongue-in-cheek, because you surely must be aware of instances where the real part of an impedance changes with frequency without significant change in the reactance.
What about the resistance of straight length of wire? This increases due to the skin effect, whereby as the frequency rises more and more of the current travels closer to the outer (indeed for circular cross-section, the only) surface of the wire, so in effect reducing the cross-sectional area of the wire. In the limit, there is also a change in the inductance per unit length too, but it is not significant compared to the change in resistance.
And although not strictly a "component", there is the free space acoustic radiation resistance of a diaphragm, which also rises with frequency up to the frequency where the circumference is approximately equal to the wavelength. I will concede in this example that the reactive part of the impedance also changes at a fair rate of knots over the same frequency interval.
I'm sure you already knew all that. But it does illustrate why it is perfect legitimate to seek frequency-dependent resistance models.
Regards,
Tony
|
Re: Freqeucny Dependent resistor
There is a whole field of active filter synthesis based on FDNR
(Frequency Dependent Negative Resistance).... LTspice makes it easier to
synthesize...
<>
cheers
A. Ganesan
=================================================================================
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On 9/15/2011 2:13 PM, Christian Thomas wrote: Well, that's a question AG.
Might we not be looking at a naive question here? Ie. Can I please have a
resistor that changes with frequency but with none of those nasty reactive
elements? If that's the case then looking in the s-plane is not the answer
being sought.
In which case the answer needed is "No, you can't. Or at least you can't
have a full solution. (I think that must be right). But we do have some
useful reactive components that perform that function, and that's what
everyone else uses. C and L in LTSpice; and their s-plane behaviour is
built in."
CT
On 15 September 2011 19:28, Ganesan<dg1@...> wrote:
**
Should Laplace be turning in his grave?
On 9/15/2011 12:51 PM, Michael Peter Kiwanuka wrote:
Hi Shivesh,
I have not a great deal of understanding of Laplace transforms but I have a niggling feeling of the transform of an increasing ramp is (1/s**2). Which
definition of L-tranform are you usiing ?
Best regards
Michael
To: LTspice@...
From: shivesh_sl@...
Date: Wed, 14 Sep 2011 20:01:53 +0000
Subject: [LTspice] Re: Freqeucny Dependent resistor
Hi George,
Laplace transform for ramp in increasing values is (1/s). Yuo search we for this. Since we have decreasing function hence inverse of previous case,
you get (s).
since s is complex no. with value of containing (w)=2*PI()*freq hence for R_eq you multiply 2*PI() to compensate for one coming in from (w).
I hope this explanation helps. I know it is not great but probably you get gits of it.
Regards,
Shivesh
--- In LTspice@..., "George Evans"<george.evans@...> wrote:
Shivesh
many thanks - however I find the laplace expression syntax needs a bit of explanation. How can it be generalised say to model an R proportional to
square_root of frequency?
George
_____
From: shivesh_sl [mailto:shivesh_sl@...]
To: LTspice@...
Sent: Mon, 12 Sep 2011 16:47:00 +0100
Subject: [LTspice] Re: Freqeucny Dependent resistor
Hi George,
I have uploaded LTSpice schematic to our group. It should be under
msg:49523 heading. Please look it up. If you look up impedance i.e. Voltage
at R2/ Current R1 it should give nice linear slope 20db per decade slope.
If you any more question please let me know.
Regards,
Shivesh.
--- In LTspice@..., "George Evans"<george.evans@> wrote:
Hi Shivesh
Interesting. Can you indicate where you placed the Laplace function
definition please? The expression I need is one where R_Freq is proprotional
to sqare root of Freq. e.g. R_Req=R_eq*K*sqrt(s). Can this go in as a spice
directive?
George
_____
From: shivesh_sl [mailto:shivesh_sl@]
To: LTspice@...
Sent: Wed, 07 Sep 2011 16:28:04 +0100
Subject: [LTspice] Freqeucny Dependent resistor
Recently I had had been trying to simulate frequency dependent resistor
in LTSpice. But was did not find solution on internet. Then I tried
performing simulation by inserting behavioral voltage and current sources.
But was having problems with it. Following solution was achieved after
reading that Laplace transform can be used for behavioral sources.
To simulate you will need value of resistor at 1Hz =R_1
R_eq= R_1 * 2 * Pi()[3.142...]
R_Freq=R_eq Laplace (s)
Please leave space between R_eq& Laplace, Laplace& (s).
You can use this either as part of your sub circuit model (SPICE Model)
or you use them with default resistor by inserting the equation in value
field.
Same method can be used for other capacitor and inductors. I have
tested all of them and does provide with good replications.
I hope this helps.
----------------------------------------------------------
This email and any files transmitted with it are confidential and
intended solely for the use of the individual or entity to whom
they are addressed. If you have received this email in error
please notify the system manager. Please note that any views or
opinions presented in this email are solely those of the author
and do not necessarily represent those of the company. Finally,
the recipient should check this email and any attachments for
the presence of viruses. The company accepts no liability for
any damage caused by any virus transmitted by this email.
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in England and Wales. Registered number: 3154453.
Registered office: The George Business Centre, Christchurch
Road, New Milton. BH25 6QJ
------------------------------------
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|
Re: Freqeucny Dependent resistor
<snip> --- In LTspice@..., Christian Thomas <ct.waveform@...> wrote:
Well, that's a question AG.
Might we not be looking at a naive question here? Ie. Can I please have a
resistor that changes with frequency but with none of those nasty reactive
elements? If that's the case then looking in the s-plane is not the answer
being sought.
In which case the answer needed is "No, you can't. Or at least you can't
have a full solution. (I think that must be right). But we do have some
useful reactive components that perform that function, and that's what
everyone else uses. C and L in LTSpice; and their s-plane behaviour is
built in."
CT
</snip> Hello Christian, I'm sure you ask the question tongue-in-cheek, because you surely must be aware of instances where the real part of an impedance changes with frequency without significant change in the reactance. What about the resistance of straight length of wire? This increases due to the skin effect, whereby as the frequency rises more and more of the current travels closer to the outer (indeed for circular cross-section, the only) surface of the wire, so in effect reducing the cross-sectional area of the wire. In the limit, there is also a change in the inductance per unit length too, but it is not significant compared to the change in resistance. And although not strictly a "component", there is the free space acoustic radiation resistance of a diaphragm, which also rises with frequency up to the frequency where the circumference is approximately equal to the wavelength. I will concede in this example that the reactive part of the impedance also changes at a fair rate of knots over the same frequency interval. I'm sure you already knew all that. But it does illustrate why it is perfect legitimate to seek frequency-dependent resistance models. Regards, Tony
|
Re: Solid-state relay model
I have made some. They work perfect, except when I put them in a circuit, then they behave unbelievably weird. I'm working the issue.
toggle quoted message
Show quoted text
--- In LTspice@..., "supertjhok" <supertjhok@...> wrote:
Does anyone have a SPICE model of a solid-state relay, or guidance on how to create one? I'm using the PVA series from International Rectifier.
Thanks
Soumyajit
|
Re: Freqeucny Dependent resistor
In message <CANj54jwDGEMhNQA5E=DD=cMmYJTwDN=mMCrX2FaMfB4YgiLxuw@...>, dated Thu, 15 Sep 2011, Christian Thomas <ct.waveform@...> writes: In which case the answer needed is "No, you can't. Or at least you can't have a full solution. (I think that must be right). I'm not sure. We have real resistances that change with frequency - radiation resistances for example, There are definitely resistances - at any fixed frequency they are consistent with Ohm's and Joule's Laws. So why can't I define a resistor R(f), such that R(f) = kf, or K*F(f)? k and K have dimensions, of course, but that doesn't seem to be a problem. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK When I point to a star, please look at the star, not my finger. The star will be more interesting.
|
Re: Freqeucny Dependent resistor
Well, that's a question AG. Might we not be looking at a naive question here? Ie. Can I please have a resistor that changes with frequency but with none of those nasty reactive elements? If that's the case then looking in the s-plane is not the answer being sought. In which case the answer needed is "No, you can't. Or at least you can't have a full solution. (I think that must be right). But we do have some useful reactive components that perform that function, and that's what everyone else uses. C and L in LTSpice; and their s-plane behaviour is built in." CT On 15 September 2011 19:28, Ganesan <dg1@...> wrote: **
Should Laplace be turning in his grave?
On 9/15/2011 12:51 PM, Michael Peter Kiwanuka wrote:
Hi Shivesh,
I have not a great deal of understanding of Laplace transforms but I have a niggling feeling of the transform of an increasing ramp is (1/s**2). Which
definition of L-tranform are you usiing ?
Best regards
Michael
To: LTspice@...
From: shivesh_sl@...
Date: Wed, 14 Sep 2011 20:01:53 +0000
Subject: [LTspice] Re: Freqeucny Dependent resistor
Hi George,
Laplace transform for ramp in increasing values is (1/s). Yuo search we
for this. Since we have decreasing function hence inverse of previous case,
you get (s).
since s is complex no. with value of containing (w)=2*PI()*freq hence for
R_eq you multiply 2*PI() to compensate for one coming in from (w).
I hope this explanation helps. I know it is not great but probably you
get gits of it.
Regards,
Shivesh
--- In LTspice@..., "George Evans"<george.evans@...> wrote:
Shivesh
many thanks - however I find the laplace expression syntax needs a bit
of explanation. How can it be generalised say to model an R proportional to
square_root of frequency?
George
_____
From: shivesh_sl [mailto:shivesh_sl@...]
To: LTspice@...
Sent: Mon, 12 Sep 2011 16:47:00 +0100
Subject: [LTspice] Re: Freqeucny Dependent resistor
Hi George,
I have uploaded LTSpice schematic to our group. It should be under
msg:49523 heading. Please look it up. If you look up impedance i.e. Voltage
at R2/ Current R1 it should give nice linear slope 20db per decade slope.
If you any more question please let me know.
Regards,
Shivesh.
--- In LTspice@..., "George Evans"<george.evans@> wrote:
Hi Shivesh
Interesting. Can you indicate where you placed the Laplace function
definition please? The expression I need is one where R_Freq is proprotional
to sqare root of Freq. e.g. R_Req=R_eq*K*sqrt(s). Can this go in as a spice
directive?
George
_____
From: shivesh_sl [mailto:shivesh_sl@]
To: LTspice@...
Sent: Wed, 07 Sep 2011 16:28:04 +0100
Subject: [LTspice] Freqeucny Dependent resistor
Recently I had had been trying to simulate frequency dependent resistor
in LTSpice. But was did not find solution on internet. Then I tried
performing simulation by inserting behavioral voltage and current sources.
But was having problems with it. Following solution was achieved after
reading that Laplace transform can be used for behavioral sources.
To simulate you will need value of resistor at 1Hz =R_1
R_eq= R_1 * 2 * Pi()[3.142...]
R_Freq=R_eq Laplace (s)
Please leave space between R_eq& Laplace, Laplace& (s).
You can use this either as part of your sub circuit model (SPICE Model)
or you use them with default resistor by inserting the equation in value
field.
Same method can be used for other capacitor and inductors. I have
tested all of them and does provide with good replications.
I hope this helps.
----------------------------------------------------------
This email and any files transmitted with it are confidential and
intended solely for the use of the individual or entity to whom
they are addressed. If you have received this email in error
please notify the system manager. Please note that any views or
opinions presented in this email are solely those of the author
and do not necessarily represent those of the company. Finally,
the recipient should check this email and any attachments for
the presence of viruses. The company accepts no liability for
any damage caused by any virus transmitted by this email.
Gill Research& Development Ltd is a limited company registered
in England and Wales. Registered number: 3154453.
Registered office: The George Business Centre, Christchurch
Road, New Milton. BH25 6QJ
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
|
Re: Freqeucny Dependent resistor
Should Laplace be turning in his grave?
toggle quoted message
Show quoted text
On 9/15/2011 12:51 PM, Michael Peter Kiwanuka wrote: Hi Shivesh,
I have not a great deal of understanding of Laplace transforms but I have a niggling feeling of the transform of an increasing ramp is (1/s**2). Which definition of L-tranform are you usiing ?
Best regards
Michael
To: LTspice@...
From: shivesh_sl@...
Date: Wed, 14 Sep 2011 20:01:53 +0000
Subject: [LTspice] Re: Freqeucny Dependent resistor
Hi George,
Laplace transform for ramp in increasing values is (1/s). Yuo search we for this. Since we have decreasing function hence inverse of previous case, you get (s).
since s is complex no. with value of containing (w)=2*PI()*freq hence for R_eq you multiply 2*PI() to compensate for one coming in from (w).
I hope this explanation helps. I know it is not great but probably you get gits of it.
Regards,
Shivesh
--- In LTspice@..., "George Evans"<george.evans@...> wrote:
Shivesh
many thanks - however I find the laplace expression syntax needs a bit of explanation. How can it be generalised say to model an R proportional to square_root of frequency?
George
_____
From: shivesh_sl [mailto:shivesh_sl@...]
To: LTspice@...
Sent: Mon, 12 Sep 2011 16:47:00 +0100
Subject: [LTspice] Re: Freqeucny Dependent resistor
Hi George,
I have uploaded LTSpice schematic to our group. It should be under msg:49523 heading. Please look it up. If you look up impedance i.e. Voltage at R2/ Current R1 it should give nice linear slope 20db per decade slope.
If you any more question please let me know.
Regards,
Shivesh.
--- In LTspice@..., "George Evans"<george.evans@> wrote:
Hi Shivesh
Interesting. Can you indicate where you placed the Laplace function definition please? The expression I need is one where R_Freq is proprotional to sqare root of Freq. e.g. R_Req=R_eq*K*sqrt(s). Can this go in as a spice directive?
George
_____
From: shivesh_sl [mailto:shivesh_sl@]
To: LTspice@...
Sent: Wed, 07 Sep 2011 16:28:04 +0100
Subject: [LTspice] Freqeucny Dependent resistor
Recently I had had been trying to simulate frequency dependent resistor in LTSpice. But was did not find solution on internet. Then I tried performing simulation by inserting behavioral voltage and current sources. But was having problems with it. Following solution was achieved after reading that Laplace transform can be used for behavioral sources.
To simulate you will need value of resistor at 1Hz =R_1
R_eq= R_1 * 2 * Pi()[3.142...]
R_Freq=R_eq Laplace (s)
Please leave space between R_eq& Laplace, Laplace& (s).
You can use this either as part of your sub circuit model (SPICE Model) or you use them with default resistor by inserting the equation in value field.
Same method can be used for other capacitor and inductors. I have tested all of them and does provide with good replications.
I hope this helps.
----------------------------------------------------------
This email and any files transmitted with it are confidential and
intended solely for the use of the individual or entity to whom
they are addressed. If you have received this email in error
please notify the system manager. Please note that any views or
opinions presented in this email are solely those of the author
and do not necessarily represent those of the company. Finally,
the recipient should check this email and any attachments for
the presence of viruses. The company accepts no liability for
any damage caused by any virus transmitted by this email.
Gill Research& Development Ltd is a limited company registered
in England and Wales. Registered number: 3154453.
Registered office: The George Business Centre, Christchurch
Road, New Milton. BH25 6QJ
|
Re: Freqeucny Dependent resistor
Hi Shivesh, I have not a great deal of understanding of Laplace transforms but I have a niggling feeling of the transform of an increasing ramp is (1/s**2). Which definition of L-tranform are you usiing ? Best regards Michael To: LTspice@... From: shivesh_sl@... Date: Wed, 14 Sep 2011 20:01:53 +0000 Subject: [LTspice] Re: Freqeucny Dependent resistor Hi George, Laplace transform for ramp in increasing values is (1/s). Yuo search we for this. Since we have decreasing function hence inverse of previous case, you get (s). since s is complex no. with value of containing (w)=2*PI()*freq hence for R_eq you multiply 2*PI() to compensate for one coming in from (w). I hope this explanation helps. I know it is not great but probably you get gits of it. Regards, Shivesh --- In LTspice@..., "George Evans" <george.evans@...> wrote:
Shivesh
many thanks - however I find the laplace expression syntax needs a bit of explanation. How can it be generalised say to model an R proportional to square_root of frequency?
George
_____
From: shivesh_sl [mailto:shivesh_sl@...]
To: LTspice@...
Sent: Mon, 12 Sep 2011 16:47:00 +0100
Subject: [LTspice] Re: Freqeucny Dependent resistor
Hi George,
I have uploaded LTSpice schematic to our group. It should be under msg:49523 heading. Please look it up. If you look up impedance i.e. Voltage at R2/ Current R1 it should give nice linear slope 20db per decade slope.
If you any more question please let me know.
Regards,
Shivesh.
--- In LTspice@..., "George Evans" <george.evans@> wrote:
Hi Shivesh
Interesting. Can you indicate where you placed the Laplace function definition please? The expression I need is one where R_Freq is proprotional to sqare root of Freq. e.g. R_Req=R_eq*K*sqrt(s). Can this go in as a spice directive?
George
_____
From: shivesh_sl [mailto:shivesh_sl@]
To: LTspice@...
Sent: Wed, 07 Sep 2011 16:28:04 +0100
Subject: [LTspice] Freqeucny Dependent resistor
Recently I had had been trying to simulate frequency dependent resistor in LTSpice. But was did not find solution on internet. Then I tried performing simulation by inserting behavioral voltage and current sources. But was having problems with it. Following solution was achieved after reading that Laplace transform can be used for behavioral sources.
To simulate you will need value of resistor at 1Hz =R_1
R_eq= R_1 * 2 * Pi()[3.142...]
R_Freq=R_eq Laplace (s)
Please leave space between R_eq & Laplace, Laplace & (s).
You can use this either as part of your sub circuit model (SPICE Model) or you use them with default resistor by inserting the equation in value field.
Same method can be used for other capacitor and inductors. I have tested all of them and does provide with good replications.
I hope this helps.
----------------------------------------------------------
This email and any files transmitted with it are confidential and
intended solely for the use of the individual or entity to whom
they are addressed. If you have received this email in error
please notify the system manager. Please note that any views or
opinions presented in this email are solely those of the author
and do not necessarily represent those of the company. Finally,
the recipient should check this email and any attachments for
the presence of viruses. The company accepts no liability for
any damage caused by any virus transmitted by this email.
Gill Research & Development Ltd is a limited company registered
in England and Wales. Registered number: 3154453.
Registered office: The George Business Centre, Christchurch
Road, New Milton. BH25 6QJ
[Non-text portions of this message have been removed]
----------------------------------------------------------
This email and any files transmitted with it are confidential and
intended solely for the use of the individual or entity to whom
they are addressed. If you have received this email in error
please notify the system manager. Please note that any views or
opinions presented in this email are solely those of the author
and do not necessarily represent those of the company. Finally,
the recipient should check this email and any attachments for
the presence of viruses. The company accepts no liability for
any damage caused by any virus transmitted by this email.
Gill Research & Development Ltd is a limited company registered
in England and Wales. Registered number: 3154453.
Registered office: The George Business Centre, Christchurch
Road, New Milton. BH25 6QJ
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
|
--- In LTspice@..., Andy <Andrew.Ingraham@...> wrote:
Naive question. Why would you want to do that? If you have s-parameter
files, presumably they came from measurements of a real circuit. So why
ask Spice (or anything else) to generate a circuit? Often you have s-parameters for a component (a transistor or MMIC),
which you get from the component vendor, and you want to use it in a
circuit.
Andy
Indeed. And for passive products, such as SAW filters or isolators, S-parameters are the only data you're ever likely to get from vendors. Also for capacitors and inductors, vendors such as Murata and ATC also provide S-parameter data for use at frequencies at which the simple equivalent circuits we're used to in SPICE are hopelessly inadequate to describe the performance. Regards, Tony
|
In message <CALBs-ThF7REAcCQEOUOw2A8J1qBi752gUcHTrqUnBUatD03Scg@...>, dated Thu, 15 Sep 2011, Andy <Andrew.Ingraham@...> writes: Naive question. Why would you want to do that? If you have s-parameter
files, presumably they came from measurements of a real circuit. So why
ask Spice (or anything else) to generate a circuit? Often you have s-parameters for a component (a transistor or MMIC), which you get from the component vendor, and you want to use it in a circuit.
I said it was naive! The data are s-parameter values as functions of frequency, I suppose? Synthesising circuits from impedance values in any form is difficult but only very nearly impossible unless the functions of frequency are rather simple. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK When I point to a star, please look at the star, not my finger. The star will be more interesting.
|
Naive question. Why would you want to do that? If you have s-parameter
files, presumably they came from measurements of a real circuit. So why
ask Spice (or anything else) to generate a circuit? Often you have s-parameters for a component (a transistor or MMIC), which you get from the component vendor, and you want to use it in a circuit. Andy
|
Ah. Got it. It was "Edit->Edit Attributes..." I was missing.
Thanks again.
toggle quoted message
Show quoted text
--- In LTspice@..., "Helmut" <helmutsennewald@...> wrote:
--- In LTspice@..., "stm6823@" <stevemorris@> wrote:
I opened the AD8336.asy you had in the zip file with FILE OPEN in LTspice but I don't find any attributes.
When I open it in notepad the only attributes are pin references.
Version 4
SymbolType BLOCK
RECTANGLE Normal -80 -104 80 104
WINDOW 0 0 -104 Bottom 2
WINDOW 3 0 104 Top 2
SYMATTR Value AD8336
SYMATTR Prefix X
SYMATTR SpiceModel ad8336.cir
SYMATTR Value2 AD8336
PIN -80 -64 LEFT 8
PINATTR PinName GNEG
PINATTR SpiceOrder 1
PIN -80 -32 LEFT 8
etc.
How do I open the others to see what you set?
Thanks,
STM
Hello STM,
You can see my attributes in the text file above.
It's different from what you had in your your symbol.
Normally you don't look with a text editor. You should open
my symbol with LTspice and then "Edit->Edit Attributes...".
Modelfile: ad8336.cir
Value: AD8336
Value2: AD8336
Best regards,
Helmut
--- In LTspice@..., "Helmut" <helmutsennewald@> wrote:
--- In LTspice@..., "stm6823@" <stevemorris@> wrote:
Helmut,
Thank you very much for your time and help. So much for me to learn. I integrated all your schematic changes into mine and it works great. I put the changes in one at a time to observe the effect. Lots of subtle stuff like the series resistance in the supplies messing things up that I don't get.
I am curious about your reference to correcting the symbol because I am still using mine and it works OK. I had LTspice make it from the netlist editor. I tried to open yours to see what you changed but it is not editable. What did you change?
Thanks again,
STM
Hello STM,
I made a specific symbol which isn't editable.
All symbol of the LTC-opamps are made this way.
Please open the symbol(.asy) with LTspice to see which
attributes I have set.
Best regards,
Helmut
|
<snip> However, some clever contributor to this group has provided a means to plot the graticule of a Smth chart and impedance curves with frequency markers
(Files > Examples > Apps > SmithLTspice.zip).
??
With respect to LTspice handling s-parameters, it certainly can. The .NET
command computes network parameters in an AC sweep. The HELP files says in part,
??
"This statement is used with a small signal(.AC) analysis to compute the input
and output admittance, impedance, Y-parameters, Z-parameters, H-parameters, and
S-parameters of a 2-port network. It can also be used to compute the input
admittance and impedance of a 1-port network. This must be used with a .AC
statement, which determines the frequency sweep of the network analysis."
??
There is an entire section in the tutorial section of this groups files devoted
to s-parameters in LTspice (Files> Tut> S-Parameter).
??
All the best,
??
???? - Philip Hello Philip,
Thanks for the info.
I'm aware of the Smith chart add-on, which is why I said native. It's clever as you said, but not slick enough for serious design work; even the author concedes it's crude.
</snip> Other folk might like to be aware that also exist several ways of plotting Smith charts in Excel by using similar kludges. This is one of several: Regards, Tony
|
In message <j4t6tu+4c59@...>, dated Thu, 15 Sep 2011, Tony Casey <tony@...> writes: There are also various utilities that claim to generate SPICE subcircuits from S-parameter files, but this is something of a holy grail, which is why the only commercial product that really claims to have cracked this with multiport demonstrable accuracy over decades of frequency range costs thousands of dollars. Naive question. Why would you want to do that? If you have s-parameter files, presumably they came from measurements of a real circuit. So why ask Spice (or anything else) to generate a circuit? To track down parasitics? -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK When I point to a star, please look at the star, not my finger. The star will be more interesting.
|
Re: Diode Model Request for 1N5811 and 1N6628
So, here it is:
.model 1N6628 D(Is=20.73u N=2.871 Rs=11.4m Ikf=.269 Xti=3 Eg=1.11 Cjo=97p
+ Isr=49.6E-30 Bv=660 Ibv=50u Tt=74n Iave=2.3 Vpk=600 mfg=Microsemi type=Silicon)
Best regards,
Gerhard
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--- In LTspice@..., Dan Chamberlin <dachamberlin16@...> wrote:
Could someone let me know where I can find spice models for both 1N5811 and 1N6618?
?
Thanks,
?
Dan
[Non-text portions of this message have been removed]
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--- In LTspice@..., Philip Bellingham <rmhc78a@...> wrote:
Tony,
While LTspice may not be the ideal tool for RF design, it can still be quite
useful.
You are correct that it does not have native support for producing a Smith
chart. However, some clever contributor to this group has provided a means to
plot the graticule of a Smth chart and impedance curves with frequency markers
(Files > Examples > Apps > SmithLTspice.zip).
??
With respect to LTspice handling s-parameters, it certainly can. The .NET
command computes network parameters in an AC sweep. The HELP files says in part,
??
"This statement is used with a small signal(.AC) analysis to compute the input
and output admittance, impedance, Y-parameters, Z-parameters, H-parameters, and
S-parameters of a 2-port network. It can also be used to compute the input
admittance and impedance of a 1-port network. This must be used with a .AC
statement, which determines the frequency sweep of the network analysis."
??
There is an entire section in the tutorial section of this groups files devoted
to s-parameters in LTspice (Files> Tut> S-Parameter).
??
All the best,
??
???? - Philip
Hello Philip, Thanks for the info. I'm aware of the Smith chart add-on, which is why I said native. It's clever as you said, but not slick enough for serious design work; even the author concedes it's crude. I'm also aware that adding the .net directive enables an .ac analysis to generate S-parameters; and indeed, I make a lot of use of this feature. But you cannot use S-parameters as input data. This was my point, although I admit I didn't make that very clear. There are also various utilities that claim to generate SPICE subcircuits from S-parameter files, but this is something of a holy grail, which is why the only commercial product that really claims to have cracked this with multiport demonstrable accuracy over decades of frequency range costs thousands of dollars. Regards, Tony
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Re: Diode Model Request for 1N5811 and 1N6628
Oh, I just noticed that you wrote in the subject line 1N6628 and in the text 1N6618. Which one is your favourite? If you need 1N6628, I will try to create a model, too.
Gerhard
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--- In LTspice@..., Dan Chamberlin <dachamberlin16@...> wrote:
Could someone let me know where I can find spice models for both 1N5811 and 1N6618?
?
Thanks,
?
Dan
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Re: Diode Model Request for 1N5811 and 1N6628
Hello Dan,
these are approximate models for the requested diodes, newly created from the datasheets' curves/values:
.model 1N5811 D(Is=850n N=1.938 Rs=4.235m Ikf=2.584 Xti=3 Eg=1.11 Cjo=146p
+ Isr=378E-30 Bv=160 Ibv=100u Tt=43.3n Iave=6 Vpk=160 mfg=Microsemi type=Silicon)
.model 1N6618 D(Is=620.6u N=5.430 Rs=15.4m Ikf=.662 Xti=3 Eg=1.11 Cjo=192p
+ M=.414 Vj=.184 Isr=372E-30 Bv=800 Ibv=1u Tt=173n Iave=3 Vpk=800 mfg=VMI type=Silicon)
Best regards,
Gerhard Kaufmann
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--- In LTspice@..., "dachamberlin16" <dachamberlin16@...> wrote:
Could someone let me know where I can find spice models for both 1N5811 and 1N6618? I was unable to locate them in the on-line library.
Thanks,
Dan
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--- In LTspice@..., "stm6823@..." <stevemorris@...> wrote:
I opened the AD8336.asy you had in the zip file with FILE OPEN in LTspice but I don't find any attributes.
When I open it in notepad the only attributes are pin references.
Version 4
SymbolType BLOCK
RECTANGLE Normal -80 -104 80 104
WINDOW 0 0 -104 Bottom 2
WINDOW 3 0 104 Top 2
SYMATTR Value AD8336
SYMATTR Prefix X
SYMATTR SpiceModel ad8336.cir
SYMATTR Value2 AD8336
PIN -80 -64 LEFT 8
PINATTR PinName GNEG
PINATTR SpiceOrder 1
PIN -80 -32 LEFT 8
etc.
How do I open the others to see what you set?
Thanks,
STM
Hello STM, You can see my attributes in the text file above. It's different from what you had in your your symbol. Normally you don't look with a text editor. You should open my symbol with LTspice and then "Edit->Edit Attributes...". Modelfile: ad8336.cir Value: AD8336 Value2: AD8336 Best regards, Helmut
--- In LTspice@..., "Helmut" <helmutsennewald@> wrote:
--- In LTspice@..., "stm6823@" <stevemorris@> wrote:
Helmut,
Thank you very much for your time and help. So much for me to learn. I integrated all your schematic changes into mine and it works great. I put the changes in one at a time to observe the effect. Lots of subtle stuff like the series resistance in the supplies messing things up that I don't get.
I am curious about your reference to correcting the symbol because I am still using mine and it works OK. I had LTspice make it from the netlist editor. I tried to open yours to see what you changed but it is not editable. What did you change?
Thanks again,
STM
Hello STM,
I made a specific symbol which isn't editable.
All symbol of the LTC-opamps are made this way.
Please open the symbol(.asy) with LTspice to see which
attributes I have set.
Best regards,
Helmut
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Re: Diode Model Request for 1N5811 and 1N6628
--- In LTspice@..., Dan Chamberlin <dachamberlin16@...> wrote:
Could someone let me know where I can find spice models for both 1N5811 and 1N6618?
?
Thanks,
?
Dan
[Non-text portions of this message have been removed]
Hello Dan, If you can't find models for your diodes, it's not the end of the world, but it will involve more work. (But think of the satisfaction.) Firstly, for a tutorial, start here: Then, you can download Hendrik's Diode Modeler from here: Read the instructions, if necessary, then brew you own models. Create an LTspice test jig and check the curves against those in the datasheet, and you're good to go. Now you're equipped to tackle almost any diode job regardless of whether there already exists a SPICE model for the device. Note: many manufacturers' models are garbage anyway, so it's always good practice to check them in a test jig before using on anything important. There is also a VMOS modeler from the same author in the Files section. Regards, Tony
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