When talking about open source tools, here are some:
KiCad may be used as a schematic entry tool for ngspice, especially for discrete or PCB-based electronics. You may watch several simulation examples (including oscillators) here: https://forum.kicad.info/t/simulation-examples-for-kicad-ees.... KiCad integrates ngspice internally, but may also provide external ngspice with netlists for simulation.
Another GUI to ngspice is XSCHEM, especially useful for IC design work (see https://xschem.sourceforge.io/stefan/index.html). Device models are available by the Open Source PDKs from Google/Skywater, Google/GF, or IHP. A growing community is supporting digital, analog or mixed-signal design flows.
Indeed device models have to be added manually to the devices in the circuit schematic, when invoking ngspice via KiCad or QUCS-S, except for some basic devices with integrated models. Models are provided by device makers, distributors or web sites like this one: https://ngspice.sourceforge.io/modelparams.html .
KiCad may be used as a schematic entry tool for ngspice, especially for discrete or PCB-based electronics. You may watch several simulation examples (including oscillators) here: https://forum.kicad.info/t/simulation-examples-for-kicad-ees.... KiCad integrates ngspice internally, but may also provide external ngspice with netlists for simulation.
Another GUI to ngspice is XSCHEM, especially useful for IC design work (see https://xschem.sourceforge.io/stefan/index.html). Device models are available by the Open Source PDKs from Google/Skywater, Google/GF, or IHP. A growing community is supporting digital, analog or mixed-signal design flows.
QUCS-S (https://ra3xdh.github.io/) is a GUI for ngspice or XyCE.
Indeed device models have to be added manually to the devices in the circuit schematic, when invoking ngspice via KiCad or QUCS-S, except for some basic devices with integrated models. Models are provided by device makers, distributors or web sites like this one: https://ngspice.sourceforge.io/modelparams.html .