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2.3 Circuits and Subcircuits 53
{subcircuit instance name, {port connections},
Model −> subcircuit class name, Selector −> selector}
To reference a subcircuit object (see Section 3.1.8) the subcircuit class name and the selector must
be the same identifiers as those given as arguments to the Name and Selector parameters in the
corresponding Model statement. The subcircuit instance name may be any symbol or string which can
serve as the unique identifier of this instance of the subcircuit object.
You can even use subcircuit instance names which begin with an element type tag known to Analog Insydes.
A subcircuit reference with an instance identifier such as RX will never be confused with a resistor because
the reference will have been expanded before circuit equations are set up.
A netlist entry which marks a reference to an instance of the NPN transistor model
NPNTransistor/ACsimple, using the instance identifier Q1, would be written as follows:
{Q1, {connectivity},
Model −> NPNTransistor, Selector −> ACsimple}
This line does not yet specify how the instance Q1 of NPNTransistor/ACsimple should be embedded
into the surrounding circuit structure, i.e. which nodes of the latter should be connected to the
subcircuit’s port nodes. Associating external nodes with subcircuit port nodes is done by means of
a special format of the connectivity field. All entries of this field must be written as rules of the form
external node −> subcircuit port node
In our common-emitter amplifier (see Figure 3.1 in Section 2.3.1), node 1 of the top-level netlist is
connected to the base node "B" of the transistor, node 3 to the collector node "C", and node 4 to the
emitter node "E", resulting in a node-to-port mapping such as this:
{Q1, {1 −> "B", 3 −> "C", 4 −> "E"},
Model −> NPNTransistor, Selector −> ACsimple}
Since the mapping is defined by names, the relative positions of the entries in the connectivity field
are not important. We could have written the connectivity field as
equally well.
{3 −> "C", 1 −> "B", 4 −> "E"}
A Hierarchical Netlist Description of the Amplifier
Having learned how to define and how to make references to subcircuits (see Section 3.1.8), we can
now write a hierarchically structured netlist for the common-emitter amplifier from Section 2.3.1 (see
Figure 3.1).
In[1]:=