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Updated documentation reflecting changes into inductor model.

pre-master-46
pnenzi 23 years ago
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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).
* Semiconductor Capacitors::
* Semiconductor Capacitor Model (C)::
* Inductors::
* Inductor model::
* Coupled (Mutual) Inductors::
* Switches::
* Switch Model (SW/CSW)::
@ -2060,7 +2061,7 @@ in a @command{.model} line, as in the example below:
C1 15 5 cstd
C2 2 7 cstd
.model cstd cap=3n
.model cstd C cap=3n
@end example
Both capacitors have a capacitance of 3nF.
@ -2086,7 +2087,7 @@ example below:
@example
CEB 1 2 1u cap1 dtemp=5
.MODEL cap1 tc1=0.001
.MODEL cap1 C tc1=0.001
@end example
@ -2311,13 +2312,14 @@ circuit temperature and @option{dtemp}, if present.
If both @option{temp} and @option{dtemp} are specified, the latter is ignored.
@node Inductors, Coupled (Mutual) Inductors, Semiconductor Capacitor Model (C), Elementary Devices
@node Inductors, Inductor model, Semiconductor Capacitor Model (C), Elementary Devices
@subsection Inductors
General form:
@example
LYYYYYYY N+ N- VALUE <IC=INCOND>
LYYYYYYY n+ n- <value> <mname> <m=val> <scale=val> <temp=val>
+ <dtemp=val> <ic=init_condition>
@end example
@ -2328,15 +2330,191 @@ If both @option{temp} and @option{dtemp} are specified, the latter is ignored.
LSHUNT 23 51 10U IC=15.7MA
@end example
The inductor device implemented into ngspice has many enhancements over the
orginal one. @option{n+} and @option{n-} are the positive and negative element
nodes, respectively. @option{value} is the inductance in Henries.
N+ and N- are the positive and negative element nodes, respectively.
VALUE is the inductance in Henries.
Inductance can be specified in the instance line as in the examples above or
in a @command{.model} line, as in the example below:
@example
L1 15 5 indmod1
L2 2 7 indmod1
.model indmod1 L ind=3n
@end example
Both inductors have an inductance of 3nH.
The @option{m} parameter is the "multiplication factor", and can be used to
simulate "m" instances of the same kind in parallel. This parameter affects
all analyses.
The @option{scale} keyword let the designer choose a different scale for
elements. This option is not yet very useful, it will fully implemented in the
future to perform technology scaling. At present is here as a work in progress.
The operating temperature of instances can be set using the @option{temp}
option. Ngspice simulates the circuit with all components at the same single
temperature (the circuit temperature). To adjust the temperature of an
inductor instance you can define its temperature difference from the rest of
the circuit using @option{dtemp}.
If you want to simulate temperature dependence of an inductor, you need to
specify its temperature coefficients, using a @command{.model} line, like in
the example below:
@example
Lload 1 2 1u ind1 dtemp=5
.MODEL ind1 L tc1=0.001
@end example
The (optional) initial condition is the initial (timezero) value of
inductor current (in Amps) that flows from N+, through the inductor, to
N-. Note that the initial conditions (if any) apply only if the UIC
option is specified on the .TRAN analysis line.
inductor current (in Amps) that flows from @option{n+}, through the inductor,
to @option{n-}. Note that the initial conditions (if any) apply only if the
@option{UIC} option is specified on the @command{.tran} analysis line.
Ngspice calculates the nominal inductance as described below:
@tex
$$
L_{nom} = {{{\rm value} * {\rm scale}} \over m}
$$
@end tex
@ifnottex
@example
Lnom = value * scale / m
@end example
@end ifnottex
@node Inductor model, Coupled (Mutual) Inductors, Inductors, Elementary Devices
@subsection Inductor model
The inductor model contains physical and geometrical information that may be used to
compute the inductance in some special cases (solenoid, toroid) In the present
form is not very useful, but may be extended in the future to accomodate
silicon integrated inductors, an emerging technology.
@multitable @columnfractions .15 .4 .2 .1 .1
@item name @tab parameter @tab units @tab default @tab example
@item IND @tab model inductance
@tab H @tab 0.0 @tab 1e-3
@item CSECT @tab Cross section
@tab meters@math{^2} @tab 0.0 @tab 1e-3
@item LENGTH @tab Length
@tab meters @tab 0.0 @tab 1e-2
@item TC1 @tab first order temperature coeff.
@tab F/°C @tab 0.0 @tab 0.001
@item TC2 @tab second order temperature coeff.
@tab F/°C@math{^2} @tab 0.0 @tab 0.0001
@item TNOM @tab parameter measurement temperature
@tab °C @tab 27 @tab 50
@item N @tab number of turns
@tab - @tab 0.0 @tab 10
@item MU @tab relative magnetic permeability
@tab H/meters @tab 0.0 @tab -
@end multitable
The inductor has an indiuctance computed as:
If @option{value} is specified on the instance line then
@tex
$$
L_{nom} = {{{\rm value} * {\rm scale}} \over m}
$$
@end tex
@ifnottex
@example
Lnom = value * scale / m
@end example
@end ifnottex
If model inductance is specified then
@tex
$$
L_{nom} = {{{\rm IND} * {\rm scale}} \over m}
$$
@end tex
@ifnottex
@example
Lnom = IND * scale / m
@end example
@end ifnottex
If neither @option{value} nor @option{IND} are specified, then geometrical and
physical parameters are take into account:
If @option{LENGTH} is not zero:
@tex
if {\rm MU } is specified:
$$
L_{nom} = {{{\rm MU} * \mu_0 * {\rm N}^2 * {\rm CSECT}} \over {\rm LENGTH} }
$$
otherwise:
$$
L_{nom} = {{ \mu_0 * {\rm N}^2 * {\rm CSECT}} \over {\rm LENGTH} }
$$
with:
$$
\mu_{0} = 1.25663706143592e-6 {H \over m}
$$
@end tex
@ifnottex
@example
2
MU * mu * N * CSECT
0
Lnom = ------------------- if MU is specified
LENGTH
2
mu * N * CSECT
0
Lnom = -------------- if MU is not specified
LENGTH
with:
mu = 1.25663706143592e-6 H/m
0
@end example
@end ifnottex
After the nominal inducatnce is calculated, it is adjusted for temperature
by the formula:
@tex
$$
L(T) = L({\rm TNOM}) \Bigl( 1 + TC_1 (T - {\rm TNOM}) + TC_2 (T-{\rm TNOM})^2 \Bigr)
$$
where $L({\rm TNOM}) = L_{nom}$.
@end tex
@ifnottex
@example
2
L(T) = L(TNOM) [1 + TC (T - TNOM) + TC (T - TNOM) ]
1 2
where L(TNOM) = Lnom
@end example
@end ifnottex
In the above formula, "T" represents the instance temperature, which can be
explicitly using the @option{temp} keyword or os calculated using the
circuit temperature and @option{dtemp}, if present.
If both @option{temp} and @option{dtemp} are specified, the latter is ignored.
@ -2346,7 +2524,7 @@ option is specified on the .TRAN analysis line.
General form:
@example
KXXXXXXX LYYYYYYY LZZZZZZZ VALUE
KXXXXXXX LYYYYYYY LZZZZZZZ value
@end example
@ -2359,13 +2537,12 @@ option is specified on the .TRAN analysis line.
LYYYYYYY and LZZZZZZZ are the names of the two coupled inductors, and
VALUE is the coefficient of coupling, K, which must be greater than 0
@option{value} is the coefficient of coupling, K, which must be greater than 0
and less than or equal to 1. Using the 'dot' convention, place a 'dot'
on the first node of each inductor.
@node Switches, Switch Model (SW/CSW), Coupled (Mutual) Inductors, Elementary Devices
@subsection Switches

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