arbitray inpedance vs frequency spice model

Jan 07, 2010 4 Replies
M

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?


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Q

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
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J

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.
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F

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)
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M

If you want answers to these questions I suggest going to

formatting link
and search for the LTSpice group. This is a busy group, someone will know the answer.

Mark.

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