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44 2. Tutorial
the Symbolic option is given. This allows for assigning both a numerical as well as a symbolic value
to a circuit element. You will be able to assess the value of this feature better once you have learned
more about the topics described in Chapter 2.3 and Chapter 2.8.
Type
The value field option Type (see Section 3.1.4) allows you to specify the type of an element explicitly,
thus overriding the automatic type detection from an element’s reference designator. The argument
to the Type option must be the full name of a circuit element type supported by Analog Insydes
(see Chapter 4.2). The available types are listed in the global variable ElementTypes. Using the
Type option we could write a netlist entry for a resistor in the following way even though the name
Shunt does not begin with the type tag R.
{Shunt, {1, 2}, Type −> Resistor, Value −> R1}
Moreover, as Analog Insydes generates voltage and current identifiers (see Section 2.4.1) by adding
the prefixes "V$" and "I$" to the reference designators, the Type option gives us some more influence
on the names of voltages and currents. In this example, the resistor current would be named
I$Shunt, whereas it would be named I$R1 for the netlist entries from the previous two subsections.
The example below shows a more convincing application of the Type option. Assume that you have
an amplifier circuit with an output load connected between nodes out and ground, and that you
wish to calculate the amplifier’s frequency responses for both resistive and capacitive loads. You
could, of course, write two separate netlists for this purpose. On the other hand, the Type option
offers you the alternative to set up only one single netlist but with a variable load type:
amplifier =
Netlist[
{Load, {out, 0}, Type −> loadtype, Value −> loadval},
]
Then, by replacing the type variable with a concrete type name, you can set up circuit equations for
a particular type of load, e.g. for a capacitor:
CircuitEquations[
amplifier /. {loadtype −> Capacitor, loadval −> CL}]
Note that in both cases the identifier for the load current will be I$Load, regardless of the load
element type eventually selected.
Finally, the Type option helps us to correct a frequently made mistake, which usually occurs
when a netlist contains a supply voltage source named VCC. If we relied on automatic type
detection from the reference designator VCC, Analog Insydes would give us the error message
"Netlist::numnode: Expected 4 nodes but received 2 for VCCSource VCC". The reason for this
error is that VC is the type tag for voltage-controlled current sources, so Analog Insydes interprets
VCC as (VC)C and not as a voltage source V(CC). This problem can be easily solved by means of the
Type directive: