Subcircuits in LTSPICE

SPICE & LTSPICE, Subcircuits

Your simulation is as good as quality of the models you are using!

At least it is no better than that. This is the reason why I would like to dig into LTSPICE Subcircuit topic and create a simple reference. I’m using it myself and hope it will save you some time also. Though, there is nothing new in this tutorial and most information is just recollection of different parts of LTSPICE and SPICE3 documentation.

What subcircuits are, why we use them?

• Subcircuits are commonly used building blocks of  SPICE circuits
• Subcircuits allow to enhance functionality of built-in SPICE models
• Component vendors provide models of their parts in the form of subcircuits
• Subcircuits allow reuse of portions of a schematic in different simulations
• Subcircuits improve readability of simulated circuit

Why it is important to understand how to interpret, create and use subcircuits?

• Models, supplied by component vendors should not be treated as “trusted black box”
• Designer should clearly understand the limitations of models used
• Without this understanding your simulation is useless, because you don’t know what you are simulating

LTSPICE Subcircuits-Table of Content

• Introduction
• Subcircuit structure
• Schematic Integration of Subcircuit into LTSPICE
• Hierarchical Blocks in LTSPICE
• Converting subcircuit netlist to schematic

Reference materials:

“Creating Subcircuits and Hierarchical Blocks in LTspice” by Mike Kelsch

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