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124 2. Tutorial
Vic
1 2
L1
C1
R1
Iout
Figure 7.4: Oscillator circuit with initial condition
We start with writing a circuit netlist which includes the initial condition of the capacitor C1.
In[24]:= oscillator =
Netlist[
{L1, {0, 1}, Symbolic −> L1, Value −> 1.*10^−5},
{C1, {1, 2}, Symbolic −> C1, Value −> 3.*10^−7,
InitialCondition −> 0.002},
{R1, {2, 0}, Symbolic −> R1, Value −> 1.}
]
Out[24]= NetlistRaw, 3
Following, we distinguish two alternatives for considering initial conditions of dynamic circuit
elements.
Initial Conditions for some Dynamic Elements
With the option setting InitialConditions −> Automatic the function CircuitEquations can be
instructed to use initial conditions for those elements for which such a condition has been specified
in the netlist entry. All others are then computed consistently by NDAESolve. For our example, we
set up a system of modified nodal equations from the circuit configuration at the time t ⩵ .
In[25]:= oscillatorMNA1 = CircuitEquations[oscillator,
AnalysisMode −> Transient, ElementValues −> Symbolic,
InitialConditions −> Automatic];
DisplayForm[oscillatorMNA1]
Out[26]//DisplayForm=
I$L1t C1 V$1 ′ t V$2 ′ t ⩵⩵ 0,
V$2t
C1 V$1 ′ t V$2 ′ t ⩵⩵ 0, V$1t L1 I$L1 ′ t ⩵⩵ 0,
R1
V$10 V$20 ⩵⩵ 0.002, V$1t, V$2t, I$L1t,
DesignPoint L1 0.00001, C1 3. 10 7 , R1 1.