SLiCAP Manual
Welcome to the version 5 manual of SLiCAP. This edition surpasses all previous versions and has been completely rewritten.
SLiCAP is a S ymbolic Li near C ircuit A nalysis P rogram, is designed to set up and solve equations for analog circuit design and automatically update design data in documentation.
SLiCAP is written in Python.
SLiCAP is distributed under the MIT license
SLiCAP statistics
SLiCAP training courses
What you can find in this manual
Below, you find short descriptions of the main sections of this manual, listed in the side menu.
SLiCAP Version 5
SLiCAP Version 5 includes:
An introduction to SLiCAP
Release Notes
A short guidance how to use SLiCAP in conjunction with Structured Electronic Design
A list of contributers to SLiCAP.
SLiCAP User Guide
The User Guide provides a comprehensive guide to using SLiCAP, covering everything from installation to executing fully documented design projects.
SLiCAP output displayed in this SLiCAP user guide, is generated with the script: manual.py.
#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Manual.py: SLiCAP scripts for the HTML help file
"""
from SLiCAP import initProject
initProject("Manual")
# Import scripts for HTML help
from circuit import *
from specifications import *
from parameters import *
from models import *
from subcircuits import *
from matrix import *
from laplace import *
from pz import *
from ttime import *
from noise import *
from dcvar import *
from feedback import *
from balanced import *
from math import *
from ngspice import *
from plots import *
Warning: running this script may take a while!
This is because:
feedback.pyCompares symbolic circuit analysis results obtained with the asymptotic-gain feedback model with the results obtained from Modified Nodal Analysis. The sole purpose of this is to illustrate the correctness of the feedback model for those unacquainted with it. As stated in How to Use SLiCAP, working with such complex multi-variable expressions is not encouraged.The script
plots.pyshows a plot of a periodic pulse response obtained from a single unit step response. Periodic pulses created in this way use the Heaviside function. The numeric evaluation of expressions with this function may take a while.
SLiCAP Examples and Tutorials
SLiCAP Examples and Tutorials gives descriptive links to github SLiCAPexamples.
SLiCAP Netlist syntax
The SLiCAP netlist syntax slightly deviates from standard SPICE. SLiCAP Netlist Syntax describes the netlist syntax, including all built-in devices and models.
SLiCAP Reference
SLiCAP Reference documents all SLiCAP user callable functions and objects.
Structured Electronic Design Environment
SLiCAP Version 5 adds a graphical environment on top of the analysis engine. It is documented in its own manual: Structured Electronic Design Environment.
The GUI for creating SLiCAP instructions
Everything SLiCAP can do is driven from Python instructions, and that is where the friction has always been: a designer who knows exactly which transfer to evaluate still has to get the syntax right - the analysis function, a circuit object, a transfer type with the source, detector and loop-gain reference it requires, parameter substitution, stepping.
The Structured Electronic Design Environment is the graphical front end that removes that burden. You draw the circuit and compose the instructions through dialogs which offer only what the circuit in front of you actually has - its sources, its detectors, its controlled sources, its parameters - so an instruction is correct by construction rather than by proofreading. It does not design your circuit: it removes the clerical work around it.
Its product is an ordinary instruction file: a Python script you can read, edit by hand, run from the command line, or import from a design script, which puts the full symbolic and numeric analysis of your circuit at your disposal for design automation, verification and generated documentation. The same drawing serves as the runnable netlist and as the publication figure, and both SLiCAP and NGspice analyses live in one project.
SLiCAP installs it: pip install slicap, or pip install slicap --upgrade
to update an existing installation (see
Installation). Start it with slicap for the
full environment, or with slicap-schematics to edit schematics only.
Design with SLiCAP, verify with NGspice
Design and verification use the same relation in opposite directions, and that is why they need different models.
Designing moves forward: from a specification, through budgets, to a circuit structure and the values of its components. What has to be inverted is not the design process but the analysis. Symbolic analysis expresses performance as a function of the structure and the component values; a designer has the required performance and needs the values. With the specification and its budgets, and with methods for generating candidate structures, those values are solved from the analysis result - which is possible only while the result is symbolic and the model is simple enough to be solved: a nullor, an ideal amplifier, a first-order transistor model. That is why SLiCAP is symbolic, why it works on the simplest model that still answers the design question under study, and why a design can be built up stepwise, each decision following from the one before it and documented as it is taken.
Verification uses the same relation in its natural direction: from a given structure with given component values to the performance that results - now with the extensive device models the manufacturer or the foundry supplies, with their non-linearities, their parasitics and their temperature behaviour. That is what NGspice is for, and it is why the environment carries both: the same editor draws SLiCAP and NGspice schematics, one instruction file holds the circuits and instructions of both, and both kinds of result arrive in the same form.
Because they arrive in the same form, they can be compared directly. The transfer of a concept, derived symbolically from a handful of ideal elements, and the transfer of the completed circuit, simulated with full device models, can be drawn on the same axes of the same figure - and NGspice’s operating point is annotated on the schematic itself, node by node, down into the subcircuits. So the closing question of any design - does the realisation still do what the concept promised, and where does it start to deviate? - is answered by reading one figure, not by reconciling two separate documents. This is what makes it an integrated design and verification environment rather than a drawing tool with a simulator attached.