Ngspice

Ngspice is a mixed-level/mixed-signal circuit simulator. It is the Open Source successor of Spice3f5. A small group of maintainers and the community of motivated users contribute to the ngspice project by providing new features, enhancements and bug fixes.

Ngspice is based on three free software packages: Spice3f5, Xspice and Cider1b1:

• SPICE is the origin of all electronic circuit simulators, its successors are widely used in the electronics community.
• Xspice is an extension to Spice3 that provides additional C language code models to support analog behavioral modeling and co-simulation of digital components through a fast event driven algorithm.
• Cider adds a numerical device simulator to ngspice. It couples the circuit level simulator to the device simulator to provide enhanced simulation accuracy (at the expense of increased simulation time). Critical devices can be described with their technology parameters (numerical models), all others may use the original ngspice compact models.

Ngspice is, anyway, more than the simple sum of the packages above, as many people are contributing to the project with their experience, their bug fixes and their improvements giving ngspice additional features and improved robustness.

Status of Ngspice simulator

Ngspice implements three classes of analysis:

• Nonlinear DC analyses
• Nonlinear Transient analyses
• Linear AC analyses

Transient analysis includes transient noise simulation. AC analysis includes small signal noise simulation, pole-zero and transfer function analysis.

Ngspice implements various circuits elements, like resistors, capacitors, inductors (single or mutual), transmission lines and a growing number of semiconductor devices like diodes, bipolar transistors, mosfets (both bulk and SOI), mesfets, jfet and HFET.

New models can be added to the simulator using:

• Behavioral modeling: Internal B-, E-, and G-sources as well as R, C and L devices offer modeling by mathematical expressions, driven by node voltages, branch currents, parameters and constants.
• The Xspice codemodel interface: This is a C-code interface that helps the modeling process by simplifying the access to simulator's internal structure.
• ADMS verilog model compiler: The ADMS model compiler generates C-code from Verilog-A model descriptions for integration into ngspice.
• C language coded models with spice format: As an open source project Ngspice allows new models to be linked to the sources and compiled.

Ngspice supports parametric netlists (i.e. netlists can contain parameters and expressions). Parametric macromodels, often released by manufacturers, can be imported as-is into the simulator. The old Spice2 netlists containing polynomial sources are correctly parsed. Ngspice provides an internal scripting language to facilitate complex simulation and evaluation control flows.

Ngspice is licensed under the New BSD license.

External links

• Official website
• Download site
• ngspice manual