For IC-level design (transistor-level), stick to SIMetrix . For system-level power supply design (converters, inverters), SIMPLIS is your primary tool. Learning Resources
Built specifically for switching power systems. Unlike SPICE, it models components as a series of linear segments, allowing it to find the "Periodic Steady State" of a switching power supply in seconds rather than hours. simetrix-simplis-elite-8-20l
The Elite tier often includes advanced digital interfaces, allowing you to simulate mixed-signal designs by linking the analog engines with Verilog-HDL or Verilog-A models. For IC-level design (transistor-level), stick to SIMetrix