For those of you who know what this is, Micro-Cap circuit simulation software is now free.
From their website: Numerous features contribute to Micro-Cap 12's power. Among them are:
Integrated schematic editor and simulator.
Dynamic analysis updates waveforms and curves as you edit
Native digital simulator
Worst Case analysis to find the statistical and extreme limits of performance
Smoke Analysis to assess how close the circuit is to violating maximum operating limits.
Integral circuit optimizer with multiple optimization methods.
Integrated active and passive filter design function
Device library with over 33,000 parts.
Analog and digital behavioral modeling
Schematic waveform probing.
On-schematic voltage/state, current, power, and condition display
During the run plotting
Smith charts / Polar plots.
Multidimensional parameter stepping.
Monte Carlo analysis.
Performance functions and plots
Measure functions to measure circuit behavior
Optimizing parts modeler
Gummel-Poon, Mextram and Modella bipolar models
Berkeley BSIM 1, BSIM 2, BSIM3, and BSIM4 MOSFET models
The latest Philips device models, including MOS 11, 20, 31, 40, and PSP 102
Hefner IGBT model
IBIS model translator
Animated LEDs, switches, bars, meters, relays, stoplights, and DC motors
Lossy transmission lines
Jiles-Atherton nonlinear magnetics model
PCB interface to popular packages
Transient analysis - for investigating time domain circuit behavior
AC analysis - for investigating small signal behavior
DC analysis - for plotting static DC variables
Transfer Function analysis - for calculating the DC transfer function
Stability analysis - to find the stability limits for linear circuits
Harmonic distortion analysis
Intermodulation distortion analysis
Extensive mathematical operators and variables.