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2.4 Setting up and Solving Circuit Equations 81
a special storage mechanism for sparse matrices. Nevertheless, some commands (e.g. ACAnalysis)
rely on the fact that the equation system is formulated in matrix representation.
FrequencyVariable
The option FrequencyVariable −> symbol specifies the symbol which Analog Insydes uses to denote
the differential operator, i.e. the complex frequency, in the Laplace domain. By default, this is the
symbol s, but if you prefer to use another symbol for this purpose, for instance p, you can replace
s by p as follows:
In[16]:= CircuitEquations[rlcfilter,
FrequencyVariable −> p] // DisplayForm
Out[16]//DisplayForm=
1
RA
1
RA
0 1
1 1
RA
L1 p C1 p V$1 0
1
RA
1
L1 p
0 V$2 0
. ⩵⩵
0
1
1
L1 p
L1 p
C2 p
1
RB
0 V$3 0
I$V0 V0
1 0 0 0
ElementValues
With ElementValues −> Symbolic we can instruct CircuitEquations to use the symbolic values
from the value fields of netlist entries in which a Symbolic option is given. To demonstrate the effect
of this option let’s make some enhancements to the netlist of the RLC filter circuit from Section 2.4.2
(see Figure 4.1). Using the extended value-field format (see Section 3.1.4) we specify a numerical as
well as a symbolic value for the circuit elements.
In[17]:= rlcfilter2 =
Netlist[
{V0, {1, 0}, Value −> V0, Symbolic −> V0},
{RA, {1, 2}, Value −> 1000., Symbolic −> RA},
{C1, {2, 0}, Value −> 4.7*10^−6, Symbolic −> C1},
{L1, {2, 3}, Value −> 1.0*10^−3, Symbolic −> L1},
{C2, {3, 0}, Value −> 2.2*10^−5, Symbolic −> C2},
{RB, {3, 0}, Value −> 1000., Symbolic −> RB}
];
Note that the value of the Symbolic option needs not to coincide with the reference designator
as this is the case in the example above. You can use any Mathematica expression as value to the
Symbolic field.
A call to CircuitEquations without any additional options (i.e. the default value of the
ElementValues option is used, which is Value) will then cause the numerical values to be entered
into the matrix as these are given as arguments to the Value rules.