LTspice - LTspice® is a high performance SPICE simulation software, schematic capture and waveform viewer with enhancements and models for easing the simulation of analog circuits.
MATLAB - A high-level language and interactive environment for numerical computation, visualization, and programming
TINACloud - Create Simulate and Design Circuits and their PCB layout with TINACloud
GNU Octave - GNU Octave is a programming language for scientific computing.
EasyEDA - EasyEDA - Web-based EDA suite; runs in browser.
Wolfram Mathematica - Mathematica has characterized the cutting edge in specialized processing—and gave the chief calculation environment to a large number of pioneers, instructors, understudies, and others around the globe.