Proteus 91 is popular among electronics enthusiasts and professionals due to its ease of use, affordability, and feature-rich interface. Students and hobbyists can use Proteus 91 to learn electronics and design simple circuits, while professionals can use it for complex designs and simulations.

Length matching and differential pair routing for high-speed signals.

: A brand new framework providing significantly faster performance for complex simulations and large PCB designs. Managed Libraries

If you are looking for a legitimate free version, there are two main options offered by Labcenter Electronics: