Wikipedia
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.