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72 2. Tutorial
2.4 Setting up and Solving Circuit Equations
2.4.1 Naming Conventions
Automatically Generated Voltage and Current Identifiers
From the small circuit analysis examples already presented in the previous chapters you will have
noticed that Analog Insydes automatically creates variables for voltages and currents when setting
up circuit equations from a netlist. In order to interpret the equations correctly you need to know
everything about the identifier naming scheme employed by Analog Insydes.
By default, identifiers for branch voltages and currents associated with two-terminal elements are
generated by attaching the prefixes V$ and I$ to the reference designator (Section 3.1.3) of the
corresponding circuit element, respectively. For instance, the branch voltage across and branch
current through a resistor R1 would be named V$R1 and I$R1.
Similarly, identifiers for node voltages are generated by prefixing the node names with the tag V$,
so the node voltage at node 1 would be named V$1. Although the prefix is used for branch voltages
you will not experience any name clashes among branch and node voltage identifiers, provided that
your netlists do not contain any symbolic node identifiers (Section 3.1.3) which are identical to some
reference designators. However, if you would rather like different prefixes to be used for branch
and node voltages then read the following sections to learn how to change the standard settings.
In the case of a controlled source we need to distinguish between the voltages and currents at the
controlling and at the controlled branch. While the latter quantities are given names according to the
same convention as applied to two-terminal elements, controlling voltages and currents are marked
with the prefixes VC$ and IC$. For example, the voltage across and current through the controlled
branch of a controlled source VC1 would be called V$VC1 and I$VC1 whereas the corresponding
quantities at the controlling branch would be called VC$VC1 and IC$VC1.
Changing the Default Identifier Prefixes
All identifier prefix settings can be customized by changing the corresponding option. The current
option settings can be displayed using the command Options[CircuitEquations] and can be
changed using the Mathematica command SetOptions. For instance, the command
SetOptions[CircuitEquations, BranchVoltagePrefix −> "E$"]
would change the prefix used for branch voltages from V$ to E$. The names of the prefix options
and their default settings are listed below.
NodeVoltagePrefix −> "V$"
BranchVoltagePrefix −> "V$"
BranchCurrentPrefix −> "I$"
ControllingVoltagePrefix −> "VC$"
ControllingCurrentPrefix −> "IC$"