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SPICE simulation of finite Q inductors
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Charlie Edmondson
electronics forum Guru Wannabe


Joined: 02 May 2005
Posts: 251

PostPosted: Thu Jul 20, 2006 8:21 pm    Post subject: Re: SPICE simulation of finite Q inductors Reply with quote

Jim Thompson wrote:

Quote:
On Thu, 20 Jul 2006 10:07:14 -0700, Charlie Edmondson
edmondson@ieee.org> wrote:


Jim Thompson wrote:


On Tue, 18 Jul 2006 22:50:13 GMT, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:



Jim Thompson wrote:


On 18 Jul 2006 10:00:53 -0700, "Mark" <makolber@yahoo.com> wrote:



Joel Kolstad wrote:


Those of you who simulate things like passive LC filters... when you want a
simulation that includes the finite Q effect of the inductor, do you tend to
use a model that computes the equivalent parallel resistance, Rloss, based on
the Q specified on a data sheet at a given frequency (and then use that at
*all* frequencies of your simulation, effectively creating Q(freq) )? Or do
you simply specify Q and then use that at all frequencies (creating
Rloss(freq) )?



In most cases, the Q is important only near the resonant frequency. I
use a single fixed value resistor in series with the L that sets the Q
at the frequency corresponding to the circuit resonance frequency.

Mark

In critical applications I'm inclined to use a multi-lump model to
make sure I catch any "squirrels" ;-)

...Jim Thompson


Too bad you can't make that work on Usenet. We're overrun with
squirrels. :(


I've suddenly acquired jack rabbits in my front yard. Can't figure
out where they're nesting.

...Jim Thompson

Well, you might as well just accept them, and hope your plants grow
faster than they can eat them... 8-)

Charlie


I don't think they eat cactus or mesquite ?:-)

If they do, I'll just get out the shotgun ;-)

...Jim Thompson
Young mesquite, probably. Cacti, they usually use to cover their

burrows. The problems are if you have any flowers or food plants
growning. In Borrego, we had several families, but there was only one of
the plants that they liked so well that it couldn't grow. But, once we
planted some marigolds. Lasted two days...

Charlie
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Michael A. Terrell
electronics forum Guru


Joined: 24 Mar 2005
Posts: 2291

PostPosted: Thu Jul 20, 2006 7:30 pm    Post subject: Re: SPICE simulation of finite Q inductors Reply with quote

Jim Thompson wrote:
Quote:

On Thu, 20 Jul 2006 10:07:14 -0700, Charlie Edmondson
edmondson@ieee.org> wrote:

Well, you might as well just accept them, and hope your plants grow
faster than they can eat them... 8-)

Charlie

I don't think they eat cactus or mesquite ?:-)

If they do, I'll just get out the shotgun ;-)

Jim Thompson


If they eat cacti, ship them to Lake County Florida. There is enough
there to feed millions of the willey wabbits down there. :(


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
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Jim Thompson
electronics forum Guru


Joined: 06 May 2005
Posts: 5440

PostPosted: Thu Jul 20, 2006 5:32 pm    Post subject: Re: SPICE simulation of finite Q inductors Reply with quote

On Thu, 20 Jul 2006 10:07:14 -0700, Charlie Edmondson
<edmondson@ieee.org> wrote:

Quote:
Jim Thompson wrote:

On Tue, 18 Jul 2006 22:50:13 GMT, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:


Jim Thompson wrote:

On 18 Jul 2006 10:00:53 -0700, "Mark" <makolber@yahoo.com> wrote:


Joel Kolstad wrote:

Those of you who simulate things like passive LC filters... when you want a
simulation that includes the finite Q effect of the inductor, do you tend to
use a model that computes the equivalent parallel resistance, Rloss, based on
the Q specified on a data sheet at a given frequency (and then use that at
*all* frequencies of your simulation, effectively creating Q(freq) )? Or do
you simply specify Q and then use that at all frequencies (creating
Rloss(freq) )?



In most cases, the Q is important only near the resonant frequency. I
use a single fixed value resistor in series with the L that sets the Q
at the frequency corresponding to the circuit resonance frequency.

Mark

In critical applications I'm inclined to use a multi-lump model to
make sure I catch any "squirrels" ;-)

...Jim Thompson


Too bad you can't make that work on Usenet. We're overrun with
squirrels. :(


I've suddenly acquired jack rabbits in my front yard. Can't figure
out where they're nesting.

...Jim Thompson
Well, you might as well just accept them, and hope your plants grow
faster than they can eat them... 8-)

Charlie

I don't think they eat cactus or mesquite ?:-)

If they do, I'll just get out the shotgun ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
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Charlie Edmondson
electronics forum Guru Wannabe


Joined: 02 May 2005
Posts: 251

PostPosted: Thu Jul 20, 2006 5:07 pm    Post subject: Re: SPICE simulation of finite Q inductors Reply with quote

Jim Thompson wrote:

Quote:
On Tue, 18 Jul 2006 22:50:13 GMT, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:


Jim Thompson wrote:

On 18 Jul 2006 10:00:53 -0700, "Mark" <makolber@yahoo.com> wrote:


Joel Kolstad wrote:

Those of you who simulate things like passive LC filters... when you want a
simulation that includes the finite Q effect of the inductor, do you tend to
use a model that computes the equivalent parallel resistance, Rloss, based on
the Q specified on a data sheet at a given frequency (and then use that at
*all* frequencies of your simulation, effectively creating Q(freq) )? Or do
you simply specify Q and then use that at all frequencies (creating
Rloss(freq) )?



In most cases, the Q is important only near the resonant frequency. I
use a single fixed value resistor in series with the L that sets the Q
at the frequency corresponding to the circuit resonance frequency.

Mark

In critical applications I'm inclined to use a multi-lump model to
make sure I catch any "squirrels" ;-)

...Jim Thompson


Too bad you can't make that work on Usenet. We're overrun with
squirrels. :(


I've suddenly acquired jack rabbits in my front yard. Can't figure
out where they're nesting.

...Jim Thompson
Well, you might as well just accept them, and hope your plants grow

faster than they can eat them... 8-)

Charlie
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Leon
electronics forum addict


Joined: 18 Mar 2006
Posts: 78

PostPosted: Wed Jul 19, 2006 1:51 pm    Post subject: Re: SPICE simulation of finite Q inductors Reply with quote

Joel Kolstad wrote:
Quote:
Those of you who simulate things like passive LC filters... when you want a
simulation that includes the finite Q effect of the inductor, do you tend to
use a model that computes the equivalent parallel resistance, Rloss, based on
the Q specified on a data sheet at a given frequency (and then use that at
*all* frequencies of your simulation, effectively creating Q(freq) )? Or do
you simply specify Q and then use that at all frequencies (creating
Rloss(freq) )?

For the following, assume you first calculated Rloss at a frequency f0:

The actual Q of an inductor varies with sqrt(freq) until you start approaching
self-resonance, so assuming Q is fixed, you underestimate Q above f0 and
overestimate below f0. Using just Rloss, you overestimate below f0 and
underestimate above f0.

---Joel

Coilcraft has some nice SPICE models for their inductors. You could
modify one of those.

Leon
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Leon
electronics forum addict


Joined: 18 Mar 2006
Posts: 78

PostPosted: Wed Jul 19, 2006 1:38 pm    Post subject: Re: SPICE simulation of finite Q inductors Reply with quote

Joel Kolstad wrote:
Quote:
Those of you who simulate things like passive LC filters... when you want a
simulation that includes the finite Q effect of the inductor, do you tend to
use a model that computes the equivalent parallel resistance, Rloss, based on
the Q specified on a data sheet at a given frequency (and then use that at
*all* frequencies of your simulation, effectively creating Q(freq) )? Or do
you simply specify Q and then use that at all frequencies (creating
Rloss(freq) )?

For the following, assume you first calculated Rloss at a frequency f0:

The actual Q of an inductor varies with sqrt(freq) until you start approaching
self-resonance, so assuming Q is fixed, you underestimate Q above f0 and
overestimate below f0. Using just Rloss, you overestimate below f0 and
underestimate above f0.

---Joel

Coilcraft has some nice SPICE models for their inductors. You could
modify one of those.

Leon
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RRogers
electronics forum beginner


Joined: 09 Mar 2006
Posts: 6

PostPosted: Wed Jul 19, 2006 1:18 pm    Post subject: Re: SPICE simulation of finite Q inductors Reply with quote

Joel Kolstad wrote:
Quote:
Those of you who simulate things like passive LC filters... when you want a
simulation that includes the finite Q effect of the inductor, do you tend to
use a model that computes the equivalent parallel resistance, Rloss, based on
the Q specified on a data sheet at a given frequency (and then use that at
*all* frequencies of your simulation, effectively creating Q(freq) )? Or do
you simply specify Q and then use that at all frequencies (creating
Rloss(freq) )?

For the following, assume you first calculated Rloss at a frequency f0:

The actual Q of an inductor varies with sqrt(freq) until you start approaching
self-resonance, so assuming Q is fixed, you underestimate Q above f0 and
overestimate below f0. Using just Rloss, you overestimate below f0 and
underestimate above f0.

---Joel

I can't find the original message so I will continue here. The first
order model should include the winding resistance as a series resistor,
and then compute a parrallel resistor due to the core losses. Verify
over the frequencies your interested in, materials vary a lot. In fact
if a series resistance is sufficiently accurate, you can use
pre-distortion (right term?), tilting the frequency axis, and design
the filter having perfect (inf Q) components; and then undistort the
results to get values. That sounds a little jumbled, but these days I
presume that technique is obsolere. I reliably designed a 9 pole
filter in the 70's this way; with both time and frequency requirements.


Ray
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Michael A. Terrell
electronics forum Guru


Joined: 24 Mar 2005
Posts: 2291

PostPosted: Wed Jul 19, 2006 2:01 am    Post subject: Re: SPICE simulation of finite Q inductors Reply with quote

Jim Thompson wrote:
Quote:

On Wed, 19 Jul 2006 00:20:31 GMT, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:

Jim Thompson wrote:

On Tue, 18 Jul 2006 23:23:39 GMT, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:

Jim Thompson wrote:

I've suddenly acquired jack rabbits in my front yard. Can't figure
out where they're nesting.

Jim Thompson


Be VERY careful, Jim. Eeyore sent them to spy on you!

THAT explains it ;-)

Jim Thompson


You better oil up your Uzi, he wants them to build a roundabout in
your yard.

I think the greeting sign (in Hebrew) out on the front patio will
probably drive him back ;-)

...Jim Thompson


Do you think that I should tell the little moron that I was trained
to kill with the M16, the M60, and how to use the M72, yet I've never
had to kill anyone?


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
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Jim Thompson
electronics forum Guru


Joined: 06 May 2005
Posts: 5440

PostPosted: Wed Jul 19, 2006 12:38 am    Post subject: Re: SPICE simulation of finite Q inductors Reply with quote

On Wed, 19 Jul 2006 00:20:31 GMT, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

Quote:
Jim Thompson wrote:

On Tue, 18 Jul 2006 23:23:39 GMT, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:

Jim Thompson wrote:

I've suddenly acquired jack rabbits in my front yard. Can't figure
out where they're nesting.

Jim Thompson


Be VERY careful, Jim. Eeyore sent them to spy on you!

THAT explains it ;-)

Jim Thompson


You better oil up your Uzi, he wants them to build a roundabout in
your yard.

I think the greeting sign (in Hebrew) out on the front patio will
probably drive him back ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
Back to top
Michael A. Terrell
electronics forum Guru


Joined: 24 Mar 2005
Posts: 2291

PostPosted: Wed Jul 19, 2006 12:20 am    Post subject: Re: SPICE simulation of finite Q inductors Reply with quote

Jim Thompson wrote:
Quote:

On Tue, 18 Jul 2006 23:23:39 GMT, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:

Jim Thompson wrote:

I've suddenly acquired jack rabbits in my front yard. Can't figure
out where they're nesting.

Jim Thompson


Be VERY careful, Jim. Eeyore sent them to spy on you!

THAT explains it ;-)

Jim Thompson


You better oil up your Uzi, he wants them to build a roundabout in
your yard.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
Back to top
Jim Thompson
electronics forum Guru


Joined: 06 May 2005
Posts: 5440

PostPosted: Tue Jul 18, 2006 11:25 pm    Post subject: Re: SPICE simulation of finite Q inductors Reply with quote

On Tue, 18 Jul 2006 23:23:39 GMT, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

Quote:
Jim Thompson wrote:

I've suddenly acquired jack rabbits in my front yard. Can't figure
out where they're nesting.

Jim Thompson


Be VERY careful, Jim. Eeyore sent them to spy on you!

THAT explains it ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
Back to top
Michael A. Terrell
electronics forum Guru


Joined: 24 Mar 2005
Posts: 2291

PostPosted: Tue Jul 18, 2006 11:23 pm    Post subject: Re: SPICE simulation of finite Q inductors Reply with quote

Jim Thompson wrote:
Quote:

I've suddenly acquired jack rabbits in my front yard. Can't figure
out where they're nesting.

Jim Thompson


Be VERY careful, Jim. Eeyore sent them to spy on you!


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
Back to top
Jim Thompson
electronics forum Guru


Joined: 06 May 2005
Posts: 5440

PostPosted: Tue Jul 18, 2006 11:08 pm    Post subject: Re: SPICE simulation of finite Q inductors Reply with quote

On Tue, 18 Jul 2006 22:50:13 GMT, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

Quote:
Jim Thompson wrote:

On 18 Jul 2006 10:00:53 -0700, "Mark" <makolber@yahoo.com> wrote:


Joel Kolstad wrote:
Those of you who simulate things like passive LC filters... when you want a
simulation that includes the finite Q effect of the inductor, do you tend to
use a model that computes the equivalent parallel resistance, Rloss, based on
the Q specified on a data sheet at a given frequency (and then use that at
*all* frequencies of your simulation, effectively creating Q(freq) )? Or do
you simply specify Q and then use that at all frequencies (creating
Rloss(freq) )?



In most cases, the Q is important only near the resonant frequency. I
use a single fixed value resistor in series with the L that sets the Q
at the frequency corresponding to the circuit resonance frequency.

Mark

In critical applications I'm inclined to use a multi-lump model to
make sure I catch any "squirrels" ;-)

...Jim Thompson


Too bad you can't make that work on Usenet. We're overrun with
squirrels. Sad

I've suddenly acquired jack rabbits in my front yard. Can't figure
out where they're nesting.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
Back to top
Michael A. Terrell
electronics forum Guru


Joined: 24 Mar 2005
Posts: 2291

PostPosted: Tue Jul 18, 2006 10:50 pm    Post subject: Re: SPICE simulation of finite Q inductors Reply with quote

Jim Thompson wrote:
Quote:

On 18 Jul 2006 10:00:53 -0700, "Mark" <makolber@yahoo.com> wrote:


Joel Kolstad wrote:
Those of you who simulate things like passive LC filters... when you want a
simulation that includes the finite Q effect of the inductor, do you tend to
use a model that computes the equivalent parallel resistance, Rloss, based on
the Q specified on a data sheet at a given frequency (and then use that at
*all* frequencies of your simulation, effectively creating Q(freq) )? Or do
you simply specify Q and then use that at all frequencies (creating
Rloss(freq) )?



In most cases, the Q is important only near the resonant frequency. I
use a single fixed value resistor in series with the L that sets the Q
at the frequency corresponding to the circuit resonance frequency.

Mark

In critical applications I'm inclined to use a multi-lump model to
make sure I catch any "squirrels" ;-)

...Jim Thompson


Too bad you can't make that work on Usenet. We're overrun with
squirrels. :(


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
Back to top
Jim Thompson
electronics forum Guru


Joined: 06 May 2005
Posts: 5440

PostPosted: Tue Jul 18, 2006 5:05 pm    Post subject: Re: SPICE simulation of finite Q inductors Reply with quote

On 18 Jul 2006 10:00:53 -0700, "Mark" <makolber@yahoo.com> wrote:

Quote:

Joel Kolstad wrote:
Those of you who simulate things like passive LC filters... when you want a
simulation that includes the finite Q effect of the inductor, do you tend to
use a model that computes the equivalent parallel resistance, Rloss, based on
the Q specified on a data sheet at a given frequency (and then use that at
*all* frequencies of your simulation, effectively creating Q(freq) )? Or do
you simply specify Q and then use that at all frequencies (creating
Rloss(freq) )?



In most cases, the Q is important only near the resonant frequency. I
use a single fixed value resistor in series with the L that sets the Q
at the frequency corresponding to the circuit resonance frequency.

Mark

In critical applications I'm inclined to use a multi-lump model to
make sure I catch any "squirrels" ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
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