SpiceSharpParser

A .NET library that parses SPICE netlists and simulates them using SpiceSharp. It supports a wide subset of PSpice and LTspice syntax including DC, AC, transient, noise, and operating-point analyses.

Targets: .NET Standard 2.0 / .NET 8.0

Installation

dotnet add package SpiceSharp-Parser

Or via the NuGet Package Manager:

Install-Package SpiceSharp-Parser

Quick Example

using System;
using System.Linq;
using SpiceSharpParser;

var netlist = string.Join(Environment.NewLine,
    "Low-pass RC filter",
    "V1 IN 0 AC 1",
    "R1 IN OUT 1k",
    "C1 OUT 0 1u",
    ".AC DEC 10 1 1MEG",
    ".SAVE V(OUT)",
    ".END");

// Parse
var parser = new SpiceNetlistParser();
var parseResult = parser.ParseNetlist(netlist);

// Translate to SpiceSharp objects
var reader = new SpiceSharpReader();
var spiceModel = reader.Read(parseResult.FinalModel);

// Run simulation
var sim = spiceModel.Simulations.Single();
var export = spiceModel.Exports.Find(e => e.Name == "V(OUT)");
sim.EventExportData += (sender, args) => Console.WriteLine(export.Extract());
sim.Execute(spiceModel.Circuit);

Workflow

Using SpiceSharpParser involves three steps:

1. Parse — convert a SPICE netlist string into a parse-tree model with SpiceNetlistParser.ParseNetlist().
2. Read — translate the parse-tree into SpiceSharp simulation objects with SpiceSharpReader.Read().
3. Simulate — run the SpiceSharp simulations and collect results via exports and events.

SpiceSharpModel

SpiceSharpReader.Read() returns a SpiceSharpModel containing:

Property	Description
Circuit	The SpiceSharp Circuit with all components
Simulations	List of simulation objects (DC, AC, Transient, etc.)
Exports	Signal exports created by .SAVE, .PRINT, .PLOT
XyPlots	Plot data from .PLOT statements
Prints	Tabular data from .PRINT statements
Measurements	Results from .MEAS / .MEASURE statements
Title	Netlist title (first line)
FourierAnalyses	Fourier analysis results from .FOUR statements

Supported Features

Analysis

.AC, .DC, .TRAN, .OP, .NOISE

Output

.SAVE, .PRINT, .PLOT, .MEAS / .MEASURE (TRIG/TARG, WHEN, FIND, MAX, MIN, AVG, RMS, PP, INTEG, DERIV, PARAM), and .FOUR transient Fourier post-processing with structured model.FourierAnalyses results.

Parameters & Functions

.PARAM, .FUNC, .LET, .SPARAM

Circuit Structure

.SUBCKT / .ENDS, X (subcircuit instances), .INCLUDE, .LIB, .GLOBAL, .APPENDMODEL

Simulation Control

.STEP, .MC (Monte Carlo), .TEMP, .OPTIONS, .IC, .NODESET, .ST, .IF, .DISTRIBUTION

Devices

Category	Devices
Passive	R (resistor), C (capacitor), L (inductor), K (mutual inductance), T (transmission line)
Semiconductor	D (diode), Q (BJT), M (MOSFET), J (JFET)
Sources	V (voltage), I (current) — DC, AC, PULSE, SIN / SINE, EXP, PWL, SFFM, AM, wave-file input
Controlled sources	E (VCVS), F (CCCS), G (VCCS), H (CCVS)
Behavioral	B (arbitrary behavioral source with V= or I= expressions)
Switches	S (voltage-controlled), W (current-controlled)

LTspice Compatibility

LTspice-specific behavior is opt-in so the default parser and reader behavior stays dialect-neutral:

var parser = new SpiceNetlistParser();
parser.Settings.Compatibility = CompatibilityOptions.LTspice;
var parseResult = parser.ParseNetlist(netlist);

var reader = new SpiceSharpReader();
reader.Settings.Compatibility = CompatibilityOptions.LTspice;
var model = reader.Read(parseResult.FinalModel);

LTspice mode covers syntax such as:

• .backanno and selected output/viewer options as warning no-ops
• one-argument .TRAN with a derived step policy
• scalar expression aliases and table(...) / tbl(...)
• source waveforms including EXP(...), finite-cycle PULSE(... Ncycles), finite-cycle SINE(... Ncycles), and local two-column PWL file=<path> data
• independent-source topology options: Rser, Cpar, load, and R=<value>
• model parameter aliases: resistor and capacitor models accept tc=<tc1>[,<tc2>]; voltage switches accept von / voff; current switches accept ion / ioff
• resistor instance parasitics Rser, Rpar, and Cpar
• capacitor instance parasitics Rser, Lser, Rpar, and Cpar

Topology-changing LTspice options that can be represented safely are synthesized as helper components in the parser. Behavior-changing constructs that are not represented by SpiceSharp are reported with targeted diagnostics instead of being silently ignored.

See the LTspice compatibility matrix and LTspice netlist compatibility plan for the current support classes, known gaps, and evidence policy. LTspice schematic and symbol import (.asc / .asy) is out of scope.

Custom Components

The optional SpiceSharpParser.CustomComponents package/project adds opt-in parser mappings for LTspice-style ideal diode models and nonlinear passive devices:

.model did D(Ron=0.1 Roff=1e9 Vfwd=0.7 Ilimit=10 Epsilon=10m)
D1 out 0 did

C1 out 0 Q=1u*x+100n*x*x
L1 in out Flux=1m*x+100u*x*x

Add using SpiceSharpParser.CustomComponents; and enable the mappings with reader.Settings.UseCustomComponents() before calling Read(). Ideal diode models support LTspice-style Ron, Roff, Vfwd, Vrev, Rrev, Ilimit, RevIlimit, Epsilon, RevEpsilon, M, and N behavior, while ordinary diode models still fall back to SpiceSharp's built-in semiconductor diode.

For nonlinear passives, Q= describes stored charge as a function of capacitor terminal voltage, and Flux= describes stored flux linkage as a function of inductor branch current. The local slopes dQ/dV and dFlux/dI are used for AC small-signal behavior and transient companion models. IC=, M=, and N= are supported for these custom passive forms.

See LTspice-Style Ideal Diode for syntax, scaling rules, current-law details, and the optional LTspice-backed golden tests for DC, AC, and transient parity.

See LTspice-Style Nonlinear Passives for Q= / Flux= syntax, transient behavior, scaling rules, and optional LTspice-backed golden tests for AC and transient parity.

Behavioral Modeling

VALUE={expr}, TABLE={expr}, POLY(n), B sources, source-level E / G / F / H LAPLACE transfer functions, function-style LAPLACE(input, transfer) in behavioral expressions, and a full set of built-in math functions. LAPLACE supports voltage-controlled and current-controlled forms with rational polynomials in s, including finite constant M=, TD=, and DELAY= options. Function-style calls also support call-local options, mixed-expression helper lowering, and arbitrary scalar input expressions.

Documentation

See the documentation articles for detailed guides on each statement and device type.

Building from Source

git clone https://github.com/SpiceSharp/SpiceSharpParser.git
cd SpiceSharpParser/src
dotnet build
dotnet test

License

This project is licensed under the MIT License — see the LICENSE file for details.