Design and simulation platforms typically cost a pretty penny, just look at the SolidWorks platform and you will quickly understand why. There are tools for everything from conceptual design parameters to projected materials cost and everything in between. For those that can’t afford those software suites can always turn to Maxim Integrated’s EE-SIM Design Generation and Simulation tool, which does what the name suggests. The platform allows users to input their design requirements, which automatically generates an interactive schematic where users can adjust the individual components to their specifications. Once they have selected their components, they can then simulate their designs, which result in easy to read waveforms (including Bode plots and voltage graphs). Users can even save their schematics and download them with included manufacturer part numbers. That’s quite impressive for a free design and simulation platform. It has done some heavy lifting for myself on jobs, well
More information: EE-SIM.