Updated documentation reflecting changes into inductor model.
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doc/ngspice.texi
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doc/ngspice.texi
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@ -1759,6 +1759,7 @@ in the direction of voltage drop).
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* Semiconductor Capacitors::
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* Semiconductor Capacitor Model (C)::
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* Inductors::
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* Inductor model::
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* Coupled (Mutual) Inductors::
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* Switches::
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* Switch Model (SW/CSW)::
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@ -2060,7 +2061,7 @@ in a @command{.model} line, as in the example below:
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C1 15 5 cstd
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C2 2 7 cstd
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.model cstd cap=3n
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.model cstd C cap=3n
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@end example
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Both capacitors have a capacitance of 3nF.
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@ -2086,7 +2087,7 @@ example below:
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@example
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CEB 1 2 1u cap1 dtemp=5
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.MODEL cap1 tc1=0.001
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.MODEL cap1 C tc1=0.001
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@end example
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@ -2311,13 +2312,14 @@ circuit temperature and @option{dtemp}, if present.
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If both @option{temp} and @option{dtemp} are specified, the latter is ignored.
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@node Inductors, Coupled (Mutual) Inductors, Semiconductor Capacitor Model (C), Elementary Devices
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@node Inductors, Inductor model, Semiconductor Capacitor Model (C), Elementary Devices
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@subsection Inductors
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General form:
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@example
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LYYYYYYY N+ N- VALUE <IC=INCOND>
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LYYYYYYY n+ n- <value> <mname> <m=val> <scale=val> <temp=val>
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+ <dtemp=val> <ic=init_condition>
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@end example
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@ -2328,15 +2330,191 @@ If both @option{temp} and @option{dtemp} are specified, the latter is ignored.
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LSHUNT 23 51 10U IC=15.7MA
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@end example
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The inductor device implemented into ngspice has many enhancements over the
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orginal one. @option{n+} and @option{n-} are the positive and negative element
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nodes, respectively. @option{value} is the inductance in Henries.
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N+ and N- are the positive and negative element nodes, respectively.
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VALUE is the inductance in Henries.
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Inductance can be specified in the instance line as in the examples above or
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in a @command{.model} line, as in the example below:
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@example
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L1 15 5 indmod1
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L2 2 7 indmod1
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.model indmod1 L ind=3n
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@end example
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Both inductors have an inductance of 3nH.
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The @option{m} parameter is the "multiplication factor", and can be used to
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simulate "m" instances of the same kind in parallel. This parameter affects
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all analyses.
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The @option{scale} keyword let the designer choose a different scale for
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elements. This option is not yet very useful, it will fully implemented in the
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future to perform technology scaling. At present is here as a work in progress.
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The operating temperature of instances can be set using the @option{temp}
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option. Ngspice simulates the circuit with all components at the same single
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temperature (the circuit temperature). To adjust the temperature of an
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inductor instance you can define its temperature difference from the rest of
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the circuit using @option{dtemp}.
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If you want to simulate temperature dependence of an inductor, you need to
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specify its temperature coefficients, using a @command{.model} line, like in
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the example below:
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@example
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Lload 1 2 1u ind1 dtemp=5
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.MODEL ind1 L tc1=0.001
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@end example
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The (optional) initial condition is the initial (timezero) value of
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inductor current (in Amps) that flows from N+, through the inductor, to
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N-. Note that the initial conditions (if any) apply only if the UIC
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option is specified on the .TRAN analysis line.
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inductor current (in Amps) that flows from @option{n+}, through the inductor,
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to @option{n-}. Note that the initial conditions (if any) apply only if the
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@option{UIC} option is specified on the @command{.tran} analysis line.
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Ngspice calculates the nominal inductance as described below:
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@tex
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$$
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L_{nom} = {{{\rm value} * {\rm scale}} \over m}
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$$
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@end tex
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@ifnottex
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@example
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Lnom = value * scale / m
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@end example
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@end ifnottex
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@node Inductor model, Coupled (Mutual) Inductors, Inductors, Elementary Devices
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@subsection Inductor model
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The inductor model contains physical and geometrical information that may be used to
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compute the inductance in some special cases (solenoid, toroid) In the present
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form is not very useful, but may be extended in the future to accomodate
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silicon integrated inductors, an emerging technology.
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@multitable @columnfractions .15 .4 .2 .1 .1
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@item name @tab parameter @tab units @tab default @tab example
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@item IND @tab model inductance
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@tab H @tab 0.0 @tab 1e-3
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@item CSECT @tab Cross section
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@tab meters@math{^2} @tab 0.0 @tab 1e-3
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@item LENGTH @tab Length
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@tab meters @tab 0.0 @tab 1e-2
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@item TC1 @tab first order temperature coeff.
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@tab F/°C @tab 0.0 @tab 0.001
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@item TC2 @tab second order temperature coeff.
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@tab F/°C@math{^2} @tab 0.0 @tab 0.0001
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@item TNOM @tab parameter measurement temperature
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@tab °C @tab 27 @tab 50
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@item N @tab number of turns
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@tab - @tab 0.0 @tab 10
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@item MU @tab relative magnetic permeability
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@tab H/meters @tab 0.0 @tab -
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@end multitable
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The inductor has an indiuctance computed as:
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If @option{value} is specified on the instance line then
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@tex
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$$
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L_{nom} = {{{\rm value} * {\rm scale}} \over m}
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$$
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@end tex
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@ifnottex
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@example
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Lnom = value * scale / m
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@end example
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@end ifnottex
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If model inductance is specified then
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@tex
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$$
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L_{nom} = {{{\rm IND} * {\rm scale}} \over m}
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$$
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@end tex
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@ifnottex
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@example
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Lnom = IND * scale / m
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@end example
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@end ifnottex
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If neither @option{value} nor @option{IND} are specified, then geometrical and
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physical parameters are take into account:
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If @option{LENGTH} is not zero:
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@tex
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if {\rm MU } is specified:
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$$
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L_{nom} = {{{\rm MU} * \mu_0 * {\rm N}^2 * {\rm CSECT}} \over {\rm LENGTH} }
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$$
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otherwise:
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$$
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L_{nom} = {{ \mu_0 * {\rm N}^2 * {\rm CSECT}} \over {\rm LENGTH} }
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$$
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with:
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$$
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\mu_{0} = 1.25663706143592e-6 {H \over m}
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$$
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@end tex
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@ifnottex
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@example
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2
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MU * mu * N * CSECT
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0
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Lnom = ------------------- if MU is specified
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LENGTH
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2
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mu * N * CSECT
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0
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Lnom = -------------- if MU is not specified
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LENGTH
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with:
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mu = 1.25663706143592e-6 H/m
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0
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@end example
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@end ifnottex
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After the nominal inducatnce is calculated, it is adjusted for temperature
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by the formula:
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@tex
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$$
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L(T) = L({\rm TNOM}) \Bigl( 1 + TC_1 (T - {\rm TNOM}) + TC_2 (T-{\rm TNOM})^2 \Bigr)
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$$
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where $L({\rm TNOM}) = L_{nom}$.
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@end tex
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@ifnottex
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@example
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2
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L(T) = L(TNOM) [1 + TC (T - TNOM) + TC (T - TNOM) ]
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1 2
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where L(TNOM) = Lnom
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@end example
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@end ifnottex
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In the above formula, "T" represents the instance temperature, which can be
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explicitly using the @option{temp} keyword or os calculated using the
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circuit temperature and @option{dtemp}, if present.
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If both @option{temp} and @option{dtemp} are specified, the latter is ignored.
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@ -2346,7 +2524,7 @@ option is specified on the .TRAN analysis line.
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General form:
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@example
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KXXXXXXX LYYYYYYY LZZZZZZZ VALUE
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KXXXXXXX LYYYYYYY LZZZZZZZ value
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@end example
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@ -2359,13 +2537,12 @@ option is specified on the .TRAN analysis line.
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LYYYYYYY and LZZZZZZZ are the names of the two coupled inductors, and
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VALUE is the coefficient of coupling, K, which must be greater than 0
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@option{value} is the coefficient of coupling, K, which must be greater than 0
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and less than or equal to 1. Using the 'dot' convention, place a 'dot'
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on the first node of each inductor.
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@node Switches, Switch Model (SW/CSW), Coupled (Mutual) Inductors, Elementary Devices
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@subsection Switches
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