SPICE is probably one of the best known circuit simulators around. It supports non-linear DC and transient, and linear AC analyses. To quote from its documentation, your circuits may contain "resistors, capacitors, inductors, mutual inductors, independent voltage and current sources, four types of dependent sources, lossless and lossy transmission lines (two separate implementations), switches, uniform distributed RC lines, and the five most common semiconductor devices: diodes, BJTs, JFETs, MESFETs, and MOSFETs". The program is made up of two parts: the back-end simulator and a front-end user interface, called Nutmeg, that displays information for data analysis and plotting. Spice3 is released under the BSD licence ("license"). KSPICE, also available from the above page, is based on a version of SPICE3, has "improved transient analysis of lossy transmission lines". JSPICE is a simulator for superconductor and semiconductor circuits and incorporates the Josephson junction model. Note that all the programs are released in source code form. You will need a compiler to create the executables to run on your system. For Spice3, you will need a C compiler that can compile K&R C, not ANSI C. The GNU gcc apparently works. The program works on Unix-type systems and MSDOS.
Circuit Simulator
