开云体育

<snip>

However some transient simulations take 20-30 minutes to run, and when you reload the plot settings, it gets rid of the cursors. Plus every 5-10 seconds, the plot re-autoscales as more results are added to it. I am having a fighting battle. I have also considered using min/max, but I like the scales I've chosen with 55V on the left and 550A on the right, and I'm not sure I'd get them to match as nicely.

I really want to rant, and I'm sure I want to connect someone to the output of the power supply, but to be honest, I am so thankful for LT Spice that I can only manage "Thank you Mike" :)

</snip>
Hello Alan,

Part of your problem can be sorted by disabling marching waves, either from the Simulation menu, or by adding:
.option nomarch
in the schematic. This speeds up long .tran simulations considerably.

Regards,
Tony

In message <4E733CC9.9050803@...>, dated Fri, 16 Sep 2011, ehydra <ehydra@...> writes:

But for what is the option to disable auto-scale in the menues good for? I cannot figure it out.

It puzzles me, too.
--
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.

On Fri, 16 Sep 2011 08:34:50 +0100, you wrote:

-----Original Message-----
From: LTspice@...
[mailto:LTspice@...] On Behalf Of John Fields
Sent: 16 September 2011 00:38
To: LTspice@...
Subject: Re: [LTspice] Re: Freqeucny Dependent resistor


On Thu, 15 Sep 2011 13:20:01 -0700, you wrote:

I believe it is impossible to have a physically realizable

resistor that is frequency >dependent and has no reactive component.

---
Carbon button microphone?

Well as that has a "?" I suppose its worth treating as a question, but I
guess its tongue in cheek. Its not frequency dependant as such, merely
pressure dependant.

---
As the frequency of the pressure wave increases, the corresponding
change in resistance will decrease.

Sorry I brought it up though, since it's really off-topic here.

It's on-topic at sci.electronics.design, if you'd like to continue.

--
JF

John Woodgate schrieb:

If you follow Helmut's advice and add constant voltage and current traces before you save the plot settings file, I think the problems you report do not occur.

But for what is the option to disable auto-scale in the menues good for? I cannot figure it out.

Hm.

- Henry

--
ehydra.dyndns.info

In message <j4v5a8+rsrc@...>, dated Fri, 16 Sep 2011, Alan <Yahoo@...> writes:

That is true, and I have defined the space-bar to reload the settings, so it behaves similar to in the schematic editor. I have set the scales to make it easy to compare the voltages/currents in my converters.

If you follow Helmut's advice and add constant voltage and current traces before you save the plot settings file, I think the problems you report do not occur.
--
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.

Hi there,

as already posted by Helmut a while ago, Mike Engelhardt will come over to Germany to enlighten us on his LTSpice IV world tour. Although Stuttgart and Hannover are fully booked there are a few seats left in Duesseldorf, Tuesday the 27th of September. So take your chance to get first hand information from the chief himself and register at www.setron.de. The seminar is free of charge and will start 9:30AM,end time shall be 4PM and when I am informed correctly there is no lunch box necessary.

Take your chance
Bernd

<snip>
--- In LTspice@..., "George Evans" <george.evans@...> wrote:

Guys all this is first year circuit theory. We all know and come across series to paarllel convertions of reactive networks that introduce FDR effects where the real part of the immitance function varies with freq and these are LINEAR circuits. And as no real device is devoid of inductive/capacitive parasitics ,no matter how small, freq dependancy should not be a mistery.

Nonlinear effects were the reason I started this thread for modeling such things as ferrite cores. Manufactures rountinely supply spice parameters for these devices which involve freq dependant effects related to nonlinear loss mechanisms ( hysterisis etc ) .
George

</snip>
George,

It's no more trivial than referring to the help file to find the correct syntax for using Laplace in dependent sources, which was the subject of your original question in this thread, which as far as I can determine, was actually started by Shivesh.

Regards,
Tony

--- In LTspice@..., "pindsen" <windven@...> wrote:

--- In LTspice@..., "Helmut" <helmutsennewald@> wrote:

--- In LTspice@..., "pindsen" <windven@> wrote:

Hi,

I need an BSS138 in my LTSpice simulation.
Since I can't find that component in the program itself, I need to make it.

I have done the following steps but LTspice won't simulate:

1) Downloaded a Zetex BSS138 spice subcircuit and placed it in a "BSS138.sub" file
2) The spice file is placed in c:&#92;program files&#92;LTC&#92;LTspiceIV&#92;lib&#92;sub
3) Included a nmos symbol (nmos.asy) in the design
4) Renamed the symbol to BSS138/ZTX
5) Add a spice directive command ".inc BSS138.sub"
6) Hit the run button
7) LTspice can't simulate and says "Can't find definition of model "bss138".

The Zetex spice model can be seen here:

*ZETEX BSS138 Spice Mosfet Subcircuit Last revision 11/91
*
.SUBCKT BSS138/ZTX 3 4 5
* Nodes D G S
M1 3 2 5 5 MOD1
RG 4 2 343
RL 3 5 6E6
D1 5 3 DIODE1
.MODEL MOD1 NMOS VTO=1.109 RS=1.474 RD=1.59 IS=1E-15 KP=0.597
+CGSO=23.5P CGDO=4.5P CBD=53.5P PB=1 LAMBDA=267E-6
.MODEL DIODE1 D IS=1.254E-13 N=1.0207 RS=0.222
.ENDS

Can anyone help?

Best regards
Carsten Wind
Denmark

Hello Carsten,

4a)
Ctrl-right-mouse-click on the placed symbol nmos.
Change Prefix:MN to Prefix:X

2) I always recommend to save model files in the folder of the
schematic.

Best regards,
Helmut

Hello Helmut,
Thanx for your answer.
I did what you proposed in 4a) and it worked :-) But what does it do? What is Prefix and what does a change from MN to X do?

Then, how should the .include statement look like if the model files is placed in the folder of the schematic?

Best regards
Carsten Wind

Hello Carsten,

The X prefix tells the SPICE netlister that the device is represented by a subcircuit, and not an intrinsic model.

If the subcircuit is placed in the same directory as the schematic, then the include line is simply:
.inc subcircuitfilename.ext

Regards,
Tony

--- In LTspice@..., "Helmut" <helmutsennewald@...> wrote:

Autoscaling can't be switched off. You can workaround this
by using a plot settings file which you reload after each
simulation run or you could add an upper and a lower trace,
e,g. +10V and -10V.

That is true, and I have defined the space-bar to reload the settings, so it behaves similar to in the schematic editor. I have set the scales to make it easy to compare the voltages/currents in my converters.

However some transient simulations take 20-30 minutes to run, and when you reload the plot settings, it gets rid of the cursors. Plus every 5-10 seconds, the plot re-autoscales as more results are added to it. I am having a fighting battle. I have also considered using min/max, but I like the scales I've chosen with 55V on the left and 550A on the right, and I'm not sure I'd get them to match as nicely.

I really want to rant, and I'm sure I want to connect someone to the output of the power supply, but to be honest, I am so thankful for LT Spice that I can only manage "Thank you Mike" :)

Guys all this is first year circuit theory. We all know and come across series to paarllel convertions of reactive networks that introduce FDR effects where the real part of the immitance function varies with freq and these are LINEAR circuits. And as no real device is devoid of inductive/capacitive parasitics ,no matter how small, freq dependancy should not be a mistery.

Nonlinear effects were the reason I started this thread for modeling such things as ferrite cores. Manufactures rountinely supply spice parameters for these devices which involve freq dependant effects related to nonlinear loss mechanisms ( hysterisis etc ) .
George

_____

From: Hubert Hagadorn [mailto:huhaga@...]
To: LTspice@...
Sent: Thu, 15 Sep 2011 21:20:01 +0100
Subject: Re: [LTspice] 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

----- 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

[Non-text portions of this message have been removed]








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In message <CANj54jyWx1_Dsz+T+61doGF8U1dZckc49KVUW+gkYSdzQGQJwQ@...>, dated Thu, 15 Sep 2011, Christian Thomas <ct.waveform@...> writes:

My starting question was whether radiation impedance actually held up as only real - his example of a possibility. John then slightly moved the goalposts in response by saying that they were by definition only real;

No I didn't: I said radiation *resistance*, not impedance, is real.

This is OT and I will not respond further.

--
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.

FDR happen in all manner of nonlinear devices from ferrite cores to dielectrics where losses are a function of frequency. Try to model a ferrite core losses ( both series and ||Rs) with typical data provided by manufactures you'll find loss Rs are prop to sqrt(f) . Skin effect also is a good example- in fact its hard to find an electronic device excempt from this behavior.

George

Sent: Fri, 16 Sep 2011 08:43:18 +0100
Subject: [LTspice] Re: Freqeucny Dependent resistor








Hi,

doesn't the skin effect represent a frequency dependent resistor?

Regards,
Schmocki

--- In LTspice@..., "Dave" <dave.g4ugm@...> wrote:

-----Original Message-----
From: LTspice@...
[mailto:LTspice@...] On Behalf Of John Fields
Sent: 16 September 2011 00:38
To: LTspice@...
Subject: Re: [LTspice] Re: Freqeucny Dependent resistor


On Thu, 15 Sep 2011 13:20:01 -0700, you wrote:

I believe it is impossible to have a physically realizable

resistor that is frequency >dependent and has no reactive component.

---
Carbon button microphone?

Well as that has a "?" I suppose its worth treating as a question, but I
guess its tongue in cheek. Its not frequency dependant as such, merely
pressure dependant. Its also easily simulated by feeding a "wav" file into a
voltage dependant resistor. It wouldn't be much use as a mic if it was
frequency dependant.

I think the only way to have a frequency dependant resistor is to have some
circuit that measures frequency and use the output of that to control the
voltage on Voltage Dependant Resistor, but that has lag as its hard to
measure frequency at an instant.

Of course frequency dependant components such as inductors and capacitors
derive their frequency dependence from the fact that the current flow in
them depends on the rate of change of voltage or visa versa. This property
has a dual effect, it gives the desired frequency dependence, but it also
adds the non-resistive behaviour.

Could you use some sort of gyrator circuit to produce the desired effect?

--
JF

--------------------------------------------------------------

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]

Hi,

doesn't the skin effect represent a frequency dependent resistor?

Regards,
Schmocki

--- In LTspice@..., "Helmut" <helmutsennewald@...> wrote:

--- In LTspice@..., "pindsen" <windven@> wrote:

Hi,

I need an BSS138 in my LTSpice simulation.
Since I can't find that component in the program itself, I need to make it.

I have done the following steps but LTspice won't simulate:

1) Downloaded a Zetex BSS138 spice subcircuit and placed it in a "BSS138.sub" file
2) The spice file is placed in c:&#92;program files&#92;LTC&#92;LTspiceIV&#92;lib&#92;sub
3) Included a nmos symbol (nmos.asy) in the design
4) Renamed the symbol to BSS138/ZTX
5) Add a spice directive command ".inc BSS138.sub"
6) Hit the run button
7) LTspice can't simulate and says "Can't find definition of model "bss138".

The Zetex spice model can be seen here:

*ZETEX BSS138 Spice Mosfet Subcircuit Last revision 11/91
*
.SUBCKT BSS138/ZTX 3 4 5
* Nodes D G S
M1 3 2 5 5 MOD1
RG 4 2 343
RL 3 5 6E6
D1 5 3 DIODE1
.MODEL MOD1 NMOS VTO=1.109 RS=1.474 RD=1.59 IS=1E-15 KP=0.597
+CGSO=23.5P CGDO=4.5P CBD=53.5P PB=1 LAMBDA=267E-6
.MODEL DIODE1 D IS=1.254E-13 N=1.0207 RS=0.222
.ENDS

Can anyone help?

Best regards
Carsten Wind
Denmark

Hello Carsten,

4a)
Ctrl-right-mouse-click on the placed symbol nmos.
Change Prefix:MN to Prefix:X

2) I always recommend to save model files in the folder of the
schematic.

Best regards,
Helmut

Hello Helmut,
Thanx for your answer.
I did what you proposed in 4a) and it worked :-) But what does it do? What is Prefix and what does a change from MN to X do?

Then, how should the .include statement look like if the model files is placed in the folder of the schematic?

Best regards
Carsten Wind

--- In LTspice@..., Hubert Hagadorn wrote:

I believe it is impossible to have a physically realizable
resistor that is frequency dependent and has no reactive
component.

In Laplace expressions LTspice will accept such a construct.
The key is to use the abs() function to convert the expression
to purely real. If desired this can be converted to purely
imaginary by multiplying by the sqrt(-1). For example:

V1 1 0 ac=1 ; .ac analyses always require an ac source
B1 2 0 V= V(1) Laplace 1/(1+sqrt(s/6.3)) ; half pole at 1Hz
B2 3 0 V= V(1) Laplace 1/(1+abs(sqrt(s/6.3))) ; real only version
B3 4 0 V= V(1) Laplace sqrt(-1)/(1+abs(sqrt(s/6.3))) ; imaginary

On Thu, 15 Sep 2011 13:20:01 -0700, you wrote:

I believe it is impossible to have a physically realizable resistor that is frequency >dependent and has no reactive component.

---
Carbon button microphone?

--
JF

Hi all: Okay, let me try this one. Take a transistor, bias it and have the collector and the emitter be the input and output. The signal enters the collector by a cap and the signal exits via the emitter. Somewhere, there is a frq. to Voltage IC that feeds the base of the transitor. Is this what you are looking for? Bill
To: LTspice@...
From: tony@...
Date: Thu, 15 Sep 2011 22:14:11 +0000
Subject: [LTspice] Re: Freqeucny Dependent resistor
































--- In LTspice@..., Christian Thomas <ct.waveform@...> wrote:

That's a pretty damning point!

But does it hold? You've squared up a vector quantity to get something that

by definition has no direction. Telling me that power is a scalar is surely

a starting point, not a proof that nothing reactive is there.

CT

On 15 September 2011 21:46, John Woodgate <jmw@...> wrote:

**

In message

<CANj54jz_C3C0wTdO5kkCRbVh3qDQsrda9qatksP5h1bX+ohtqA@...>,

dated Thu, 15 Sep 2011, Christian Thomas <ct.waveform@...>

writes:

But are you sure that radiation resistances are only real?

By definition: they are notionally responsible for the real power that

is radiated. Reactive elements cannot be responsible.

--

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.

Christian,



I don't think John was stating that there is no reactive part, only that power cannot be dissipated in it.



Regards,

Tony


















[Non-text portions of this message have been removed]

Correction

"*Though I do remember nothing significant in phase angle within the audio
band*" should be no significant change in resistance. I don't remember what
the reactive elements were.

CT

Tony,

I missed this reply of yours earlier. I hadn't thought of the skin effect,
though given that is the result of penetration of fields, it must have some
reactive element, surely? I did actually look into this in some depth about
a year ago in relation to inductor design but more has flowed out than
remained. (Though I do remember nothing significant in phase angle within
the audio band. But to say it was near zero required about three
assumptions to be true which might have been a stretch.)

You also succinctly cover the radiation question that John does. ka = 2 is
considered the usual limit, incidentally, though on what grounds don't know.
ka = 1 might be flat and ka = 2 might give you a bandwidth. I have usually
regarded it as an experimental result - although the equations aren't that
difficult IIRC, there may be losses that leave the practical results a
little awry. But, as you say, plenty of reactive element in there.

Christian