LTspice Analog Circuit Simulator

LTspice (formerly SwitcherCAD III) is a high-performance SPICE (Simulation Program with Integrated Circuit Emphasis) analog circuit simulation software developed by Linear Technology Corporation (now part of Analog Devices Inc., headquartered in Norwood, Massachusetts, following the $14.8 billion acquisition in March 2017). Originally created by Mike Engelhardt in 1999, LTspice has become a general-purpose analog circuit simulator widely used in the electronics industry. Key features: SPICE simulation engine based on Berkeley SPICE3 with proprietary enhancements for speed and convergence, using modified nodal analysis, adaptive time-step integration (trapezoidal and Gear methods), and Newton-Raphson iteration. Transient analysis for time-domain simulation with nanosecond resolution. AC analysis for frequency-domain Bode plots. DC sweep for DC transfer characteristics. Noise analysis for output and input noise spectral density. Monte Carlo and worst-case analysis for tolerance estimation. Step parameter for parametric sweeps across component values, temperature, or model parameters. Built-in library: over 1,000 Linear Technology/Analog Devices switching regulator IC models (LTxxx series), op-amps, comparators, references, and general-purpose models (diodes, BJTs, MOSFETs, JFETs). Schematic capture: hierarchical editor with bus connections, sub-circuits, and symbol editor. Waveform viewer: interactive probe and display with math functions, Fourier transform (FFT), and waveform arithmetic. Model generation via .model and .subckt for custom semiconductor models. SPICE netlist import/export. Optimized for switching power supply simulation with fast transient simulation. Free download (proprietary freeware). Version XVII (17) current.