Ngspice

Ngspice is an open-source mixed-level/mixed-signal electronic circuit simulator. It is a successor of the latest stable release of Berkeley SPICE, version 3f.5, which was released in 1993. A small group of maintainers and the user community contribute to the ngspice project by providing new features, enhancements and bug fixes.

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

• SPICE is the origin of most modern 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. It is the successor to CODECS.