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From: mook johnson on 6 Jan 2010 21:40
Is there a SPICE model that allows to set to define a two pin device to have
arbitraty impedance vs frequency?

I measured the impedance of a device that has a odd impedance. I'd like to
model that without making a lumped circuit with R,L,C.

Any of you guys know of such a thing or dealt with this issue in the past?



From: qrk on 7 Jan 2010 13:56
On Wed, 6 Jan 2010 20:40:25 -0600, "mook johnson" <mook(a)mook.net>
wrote:

>Is there a SPICE model that allows to set to define a two pin device to have
>arbitraty impedance vs frequency?
>
>I measured the impedance of a device that has a odd impedance. I'd like to
>model that without making a lumped circuit with R,L,C.
>
>Any of you guys know of such a thing or dealt with this issue in the past?
>
>
What Spice program are you using? You can use tables in a voltage
controlled current source in PSpice and LTspice (PSpice syntax can be
used in LTspice). Table will have frequency and complex admittance.

Here's an educational listing on how to make a resistor from a VCCS
where the resistance is controlled by a voltage.

VOLTAGE CONTROLLED RESISTOR EXAMPLE
*TO CHECK RESISTANCE, USE EXPRESSION V(2,0)/I(R1)

Vin 1 0 AC 1.0V
R1 1 2 1N ;CURRENT MONITOR

X1 2 0 4 0 VCR

*CONTROL VOLTAGE
Vadj 4 0 900V
Rjunk 4 0 1

*VOLTAGE CONTROLLED RESISTOR SUBCIRCUIT
* 1.0 VOLT = 1.0 OHM
* +------- resistor terminal +
* | +----- resistor terminal -
* | | +--- pos control node
* | | | +- neg control node
..SUBCKT VCR 1 2 3 4
G1 1 2 VALUE={V(1,2)/V(3,4)}
..ENDS VCR

..AC DEC 10 1kHz 10kHz
..PROBE
..END

====================
A VCCS table with a frequency dependent admittance will look something
like this.

..SUBCKT XDCR 1 2
G_G1 2 1 FREQ {V(2,1)}= R_I (
+ 1000 12.41u 273.5u
+ 1150 18.61u 319.4u
+ 1300 28.13u 363.7u
+ 1450 40.99u 407.5u
+ 1600 60.94u 454.5u
+ 1750 88.09u 493.1u
+ 1900 121.5u 523.9u
+ 2050 156.6u 542.4u
+ )
..ENDS XDCR


As an excercise to the student, use your Spice skills to put together
the above examples.

--
Mark
From: Jim Thompson on 7 Jan 2010 14:02
On Thu, 07 Jan 2010 10:56:11 -0800, qrk <SpamTrap(a)spam.net> wrote:

>On Wed, 6 Jan 2010 20:40:25 -0600, "mook johnson" <mook(a)mook.net>
>wrote:
>
>>Is there a SPICE model that allows to set to define a two pin device to have
>>arbitraty impedance vs frequency?
>>
>>I measured the impedance of a device that has a odd impedance. I'd like to
>>model that without making a lumped circuit with R,L,C.
>>
>>Any of you guys know of such a thing or dealt with this issue in the past?
>>
>>
>What Spice program are you using? You can use tables in a voltage
>controlled current source in PSpice and LTspice (PSpice syntax can be
>used in LTspice). Table will have frequency and complex admittance.
>
>Here's an educational listing on how to make a resistor from a VCCS
>where the resistance is controlled by a voltage.
>
>VOLTAGE CONTROLLED RESISTOR EXAMPLE
>*TO CHECK RESISTANCE, USE EXPRESSION V(2,0)/I(R1)
>
>Vin 1 0 AC 1.0V
>R1 1 2 1N ;CURRENT MONITOR
>
>X1 2 0 4 0 VCR
>
>*CONTROL VOLTAGE
>Vadj 4 0 900V
>Rjunk 4 0 1
>
>*VOLTAGE CONTROLLED RESISTOR SUBCIRCUIT
>* 1.0 VOLT = 1.0 OHM
>* +------- resistor terminal +
>* | +----- resistor terminal -
>* | | +--- pos control node
>* | | | +- neg control node
>.SUBCKT VCR 1 2 3 4
> G1 1 2 VALUE={V(1,2)/V(3,4)}
>.ENDS VCR
>
>.AC DEC 10 1kHz 10kHz
>.PROBE
>.END
>
>====================
>A VCCS table with a frequency dependent admittance will look something
>like this.
>
>.SUBCKT XDCR 1 2
>G_G1 2 1 FREQ {V(2,1)}= R_I (
>+ 1000 12.41u 273.5u
>+ 1150 18.61u 319.4u
>+ 1300 28.13u 363.7u
>+ 1450 40.99u 407.5u
>+ 1600 60.94u 454.5u
>+ 1750 88.09u 493.1u
>+ 1900 121.5u 523.9u
>+ 2050 156.6u 542.4u
>+ )
>.ENDS XDCR
>
>
>As an excercise to the student, use your Spice skills to put together
>the above examples.

Also take a look at VVC.zip on the Models page of my website.

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
From: markp on 8 Jan 2010 12:19

"Fred Abse" <excretatauris(a)invalid.invalid> wrote in message
news:pan.2010.01.07.08.56.01.325682(a)invalid.invalid...
> On Wed, 06 Jan 2010 20:40:25 -0600, mook johnson wrote:
>
>> Is there a SPICE model that allows to set to define a two pin device to
>> have
>> arbitraty impedance vs frequency?
>>
>> I measured the impedance of a device that has a odd impedance. I'd like
>> to
>> model that without making a lumped circuit with R,L,C.
>>
>> Any of you guys know of such a thing or dealt with this issue in the
>> past?
>
> You might try playing with a combination of arbitrary behavioral sources
> (B), or dependent current and voltage sources (E, F, G, and H)
>
> You can even use polynomials.
>
> RTFM ;-)
>
> --
> "Electricity is of two kinds, positive and negative. The difference
> is, I presume, that one comes a little more expensive, but is more
> durable; the other is a cheaper thing, but the moths get into it."
> (Stephen Leacock)

If you want answers to these questions I suggest going to
http://groups.yahoo.com and search for the LTSpice group. This is a busy
group, someone will know the answer.

Mark.


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