KiCad is an open source software suite for electronic design automation (EDA) - designing schematics of electronic circuits and printed circuit boards (PCB). KiCad is developed by Jean-Pierre Charras. And features an integrated environment between schematic capture, bill of...
KiCad vs Altium Designer opinions
It's free and provide very good possibilities for circuit and PCB boards design
Ease of schematic and pcb creating. BOM creation is not very good as excel templates cannot be used so this becomes a largely manual process. Most of the add-on tools cannot be added regardless of what the instructions say. Following the instructions usually ends in some sort of crash. Import/translation tools never install regardless of the instructions. But, with all of that said KiCad is still the best free alternative to Altium Designer.
The Quite Universal Circuit Simulator (QUCS) is an integrated circuit simulator allowing the simulation and graphical presentation of results of large-signal, small-signal and noise behavior in circuits.This app doesn't have any features at the moment.
LibrePCB is a free EDA software to develop printed circuit boards. It’s currently under heavy development to bring out first stable releases as soon as possible.
LibrePCB vs Altium Designer opinions
The project is still fresh, but very promising. The developers have spent a lot of time thinking about proper a library file format that avoids problems of current open source EDA suites and will make creating and sharing comprehensive parts libraries easier. It is also much better regarding usability than current alternatives like KiCAD.
LTspice IV is a high performance Spice III simulator, schematic capture and waveform viewer with enhancements and models for easing the simulation of switching regulators.
EasyEDA - Web-based and desktop EDA suite; runs in browser, Windows, Mac, or Linux. Schematic capture, Ngspice based simulation, PCB layout, custom PCB manufacturing, for electronic engineers, educators, students and hobbyists.This app doesn't have any features at the moment.
Circuit Diagram is a free application for making electronic circuit diagrams and exporting them as images. Design circuits online in your browser or using the desktop application.This app doesn't have any features at the moment.
Ngspice is a mixed-level/mixed-signal circuit simulator. Its code is based on three open source software packages: Spice3f5, Cider1b1 and Xspice. Ngspice is part of gEDA project, a full GPL'd suite of Electronic Design Automation tools.This app doesn't have any features at the moment.