DSpice
DSpice: Design and Simulation of Circuits using Spice
...Symbol Design: Designing and managing custom schematic symbols for these models.
. Schematic Capture: Drawing and designing circuits using an intuitive CAD-style schematic editor.
. Circuit Simulation: Executing simulations (OP/Tran) seamlessly using ngspice.
. Waveform Visualization: Analyzing and presenting simulation results through a dedicated waveform viewer and Prob.
. Licensed under: DSPICE is free to use "MIT";
. Open source;