Sub-Circuit Based Models
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These are models for more complex devices, such as operational amplifiers, timers, crystals, etc, that have been described using the hierarchical sub-circuit syntax.
A sub-circuit consists of SPICE elements that are defined and referenced in a fashion similar to device models. There is no limit on the size or complexity of sub-circuits and sub-circuits can call other sub-circuits. Each sub-circuit is defined in a sub-circuit file (*.ckt).
The following sub-circuit based device model examples are covered in this section: