  Ngspice F.A.Q.Version 2.9 (ngspice-45 release)

  Maintained by Holger Vogt
  Last update: Aug 29 2025

  This document contains the Frequently Asked Questions (and Answers)
  for ngspice project.
  __________________________________________________________________________

  Table of Contents


  1. INTRODUCTION AND GENERAL INFORMATION
     1.1 What is ngspice?
     1.2 What is sharedspice?
     1.3 What is tclspice ?
     1.4 Why resurrecting Berkeley's Spice?
     1.5 What is the project's goal?
     1.6 What you are going to do?
     1.7 Legal issues
     1.8 Discussion groups
     1.9 What mailing lists exist for ngspice?
     1.10 Are the mailing lists archived anywhere?
     1.11 Where can I get a copy of ngspice?
     1.12 Where should I look on the World Wide Web for ngspice stuff?
     1.13 Where should I look on the World Wide Web for Spice documentation?
     1.14  Are there some (official) tutorials available?

  2. DEVELOPMENT
     2.1 What is the current version?
     2.2 What are the latest features in the current release?
     2.3 What does it look like?
     2.4 Who are the authors of ngspice?
     2.5 How can I report a bug/request for a feature?
     2.6 How can I join the development?

  3. SOLUTIONS TO COMMON MISCELLANEOUS PROBLEMS
     3.1 What systems are supported?
     3.2 I get errors when I try to compile the source code, why?
     3.3 This document didn't answer my question. Where else can I look for
         an answer?

  4. ADMINISTRATIVE INFORMATION AND ACKNOWLEDGEMENTS
     4.1 Feedback
     4.2 Formats in which this FAQ is available
     4.3 Authorship and acknowledgements
     4.4 Disclaimer and Copyright


  ______________________________________________________________________

  1.  INTRODUCTION AND GENERAL INFORMATION



 1.1 What is ngspice ?

  Ngspice is a mixed-level/mixed-signal circuit simulator, based on three
  open source software packages: Spice3f5, Cider1b1 and Xspice, and
  including many bug fixes and enhancements:

  - Spice3 is a widely used circuit simulator. It was developed by the
    University of California at Berkeley (UCB), by "a cast of thousand"
    (as they say) initially under the guide of Donald O. Peterson.

  - Cider is a mixed-level simulator that already includes Spice3f5 and
    adds a device simulator to it: DSIM. Cider couples the circuit level
    simulator to the device simulator to provide greater simulation
    accuracy (at the expense of greater simulation time). Critical
    devices can be described with technology parameters (numerical
    models) and non critical ones with the original spice's compact
    models.

  - Xspice is an extension to Spice3 that provides code modeling support
    and simulation of analogue components and especially of digital
    components through an embedded event driven algorithm.

  The NG prefix has lot of meanings: Next Generation, New (and) Good, etc.
  Choose or invent the one you prefer. The heart of the project is the
  ngspice program, with its tremendous advancements.


 1.2 What is sharedspice ?

  Sharedspice is an interface option to ngspice. It compiles the simulator
  into a shared object (or dynamic link library), providing full control
  over ngspice to any suitable controlling program (GUI, optimizer,
  development system, etc., to be provided by the user).


 1.3 What is tclspice ?

  Tclspice is a another interface option of ngspice, offering a tcl/tk
  interface to the user. Tclspice is both a batch and interactive simulator
  and a building block for simulator applications. Analyses can be run
  from a tcl script and vector plotted or post processed using tcl. A small
  GUI may be built by the user to analyze a circuit or a set of circuits.
  Tclspice is obtained by compiling ngspice after activating an additional
  option. This feature has not been used and tested for some time now.


 1.4 Why resurrecting Berkeley's Spice?

  Berkeley's Spice can be considered the father of most circuit
  simulators available today. It is an old but still good piece of
  software, it may not be the fastest or the most reliable but it's
  free, it's available in source code and most of the electrical
  simulators inherited it's syntax. Spice3 is based on proven numerical
  algorithms (most commercial implementations have only strengthened
  them), implements many of the models for MOSFET submicron design
  and has a powerful set of analyses. The readily availability of
  its source code in the past made this simulator the de-facto standard.


 1.5 What is the project's goal?

  Ngspice is both a maintenance and enhancement project. It is a maintenance
  project because it aims to provide the free EDA community the best spice3
  simulator available. This means fixing bugs, adding new features but always
  in the spice3 framework. Achieving compatibility with commercial spice based
  simulators and provide users the latest devices models are important goals
  of the project. Improvements in the postprocessing (data handling
  capabilities) and user interface are other goals.


 1.6 What are you going to do?

  An official roadmap for ngspice was never drawn. Contributions made by
  developers drive ngspice development and the roadmap is built day by
  day by developers writing on the lists. Ngspice development activity
  can be summarized in 3 points:

  + Compatibility: Ngspice should be compatible with commercial products,
    thus allowing people to use the netlist generated for such tools. As
    most of the commercial simulators available tracked each other in netlist
    language, this should not be an impossible task. The most important goal
    here is to provide a reliable support for model libraries coming from
    foundries. Some compatibility switches are available.

  + Compact models:  The interest in using ngspice is intimately connected
    to the available models. To provide the latest models available for
    active and passive devices is a fundamental goal of the project. In
    this direction we are integrating OSDI interface into ngspice for
    reading OpenVAF compiled Verilog-A compact models.

  + Documentation: Commercial simulators come with very good manuals
    containing tutorials, description of models equations, example of
    use, suggestions, etc. Spice came with little documentation. The
    Spice3f manual, available on the Internet has been used as the basis
    for the ngspice manual. It will be constantly improved during ngspice
    development. The ngspice manual today contains description of all
    features ngspice is offering. It is however not a tutorial of ngspice
    usage, but there are several good ones available on the internet
    (see https://ngspice.sourceforge.io/tutorials.html).


 1.7 Legal issues

  The ngspice base license is new BSD, as provided by UCB. For some parts
  of the code other compatible licences apply. All licenses are DFSG
  compatible. Please see file COPYING for details.


 1.8  Discussion groups

  Vivid discussion are going on in the ngspice discussion groups.
  They are found at https://sourceforge.net/p/ngspice/discussion/
  A special group 'ngspice tips and examples' will present interesting
  ngspice tips (your input is welcome!)


 1.9  What mailing lists exist for ngspice?

  Mailing lists have somewhat lost importance compared to the
  discussion groups described above.

  There are two general mailing lists dedicated to the ngspice project.

  Users mailing list: <ngspice-users@lists.sourceforge.net>
  This list is for ngspice users. Examples, problems, bug reports
  and general discussion on ngspice can be sent here.

  Developers mailing list: <ngspice-devel@lists.sourceforge.net>
  The list is dedicated to ngspice development. Developers should
  subscribe here, to follow the program development. May be used
  to send patches, and technical discussion on ngspice.

  Send an empty message with Subject "help" to the following addresses
  to get instructions.

  <ngspice-users-request@lists.sourceforge.net>
  <ngspice-devel-request@lists.sourceforge.net>

  Send an empty message to the following address to Subscribe.

  <ngspice-users-join@lists.sourceforge.net>
  <ngspice-devel-join@lists.sourceforge.net>

  Documentation about the user interface of
  these mailing lists can be found at:
     http://www.gnu.org/software/mailman/mailman-member


 1.10  Are the mailing lists archived anywhere ?

  Yes, the lists are archived. There are two places where to look for
  archives. The project started on the IEEE Central and South Italy
  web server and then moved to sourceforge. Sourceforge provides an
  archiving service that cam be accessed via the summary page:

  https://sourceforge.net/p/ngspice/mailman/


 1.11  Where can I get a copy of ngspice?

  You can download ngspice source code or MS Windows executables from:

  https://sourceforge.net/projects/ngspice/files/ng-spice-rework/
  
  Nearly all OS distributions for MINGW, Cygwin, Linux, macOS and
  others offer install-ready copies of ngspice. Please see
  https://repology.org/project/ngspice/packages for packages
  available.


 1.12  Where should I look on the World Wide Web for ngspice stuff?

  Have a look at the official Ngpice Web Page:

  https://ngspice.sourceforge.io


 1.13  Where should I look on the World Wide Web for Spice documentation?

  There is a detailed ngspice manual available at:
  https://ngspice.sourceforge.io/docs.html

  Others docs are assembled at:
  https://ngspice.sourceforge.io/literature.html
  https://ngspice.sourceforge.io/tutorials.html
  https://ngspice.sourceforge.io/books.html


 1.14  Are there some (official) tutorials available?
 
  Yes, they are, for ngspice, ngspice within KiCAD and on eletro-thermal
  simulation. You may find them at:
  https://ngspice.sourceforge.io/tutorials.html



  2.  DEVELOPMENT


 2.1.  What is the current version?

  The latest version released is:

  ngspice-45 (released on August 31, 2025)


 2.2.  What are the latest features in the current release?

  Please see file NEWS accompaniing this FAQ.


 2.3.  What does it look like?

  Ngspice, as the original Spice3 (and Xspice and Cider) is a command
  line simulator, but with a graphics output capability. Excellent
  open source third party tool for schematic capture (KiCad, XSCHEM, 
  Qucs-S and others) are available.


 2.4.  Who are the authors of ngspice?

  The development is open to anyone who wish to contribute. If the
  original Spice3 was made with the contribution of "a cast of
  thousand", ngspice can only increase that number. An incomplete
  list of contributor makes the "acknowledgements" page of the ngspice
  manual.


 2.5.  How can I report a bug/request for a feature?

  The ngspice summary page (hosted on Sourceforge) has bug-reporting,
  feature-request and bugs trackers. You can use them or subscribe to
  mailing lists and post there. The former is preferred since almost
  it allows to track all necessary actions upon a bug. The web site at
  https://ngspice.sourceforge.io/bugrep.html will give you more details.


 2.6.  How can I join the development?

  To join the development just code the feature you want to add and send
  your patch to the dev discussion group, open a ticket at the ngspice
  Patches page or post a merge request
  with Sourceforge.  Before you start coding check the
  latest development release of ngspice from our git repository.
  It might be that your feature has already been implemented.

  There is no bureaucracy here.



  3.  SOLUTIONS TO COMMON MISCELLANEOUS PROBLEMS


 3.1.  What systems are supported?

  Ngspice is written in C, C++, and uses some GNU extensions. You may use
  a GNU C/C++ compiler and a LINUX environment to compile it. Ngspice can
  be compiled under Windows using the mingw or cygwin environment as
  well as MS Visual Studio. It will readily compile on macOS, Intel CPUs or
  Apple M1 - M4. Wasm, FreeBSD or Solaris will do, but are not officially
  supported.


 3.2.  I get errors when I try to compile the source code, why?

  This is a one-million-euros question :).

  Write to the user's discussion group describing the problem and providing
  information on the type of hardware, the flavour of operating system.


 3.3.  This document didn't answer my question. Where else can I look
        for an answer?

  Read old messages from the mailing list archive, search the web site
  or read the docs.  Upgrade to the latest version of ngspice, many
  problems are fixed in the new versions.  If you still can't find an
  answer, post your question to the mailing lists.



  4.  ADMINISTRATIVE INFORMATION AND ACKNOWLEDGEMENTS


 4.1.  Feedback

  Send your comments about this F.A.Q. to:
  https://sourceforge.net/p/ngspice/discussion/127605/


 4.2.  Formats in which this FAQ is available

  This document is available only in ASCII format in the ngspice source
  package.


 4.3.  Authorship and acknowledgements

  Parts of the questions and answers originate from Paolo Nenzi
  and are updated by Holger Vogt.


 4.4.  Disclaimer and Copyright

  Copyright: Holger Vogt, 2025
  License: Creative Commons Attribution Share-Alike (CC-BY-SA) v4.0.
  This document is provided as is. The information in it is not
  warranted to be correct: you use it at your own risk.
