spice (simulation program with integrated circuit emphasis)

SPICE (Simulation Program with Integrated Circuit Emphasis) Overview SPICE is the standard circuit simulation engine used to verify analog, digital, and mixed-signal IC designs by numerically solving circuit equations. Developed at UC Berkeley in 1973, it remains the foundation of all circuit simulation. What SPICE Does - DC Analysis: Find the operating point (bias conditions) of the circuit. - AC Analysis: Frequency response (gain, phase, bandwidth) using linearized small-signal models. - Transient Analysis: Time-domain simulation of circuit response to input signals. Most computationally intensive. - Monte Carlo: Statistical variation analysis—run many simulations with randomly varied parameters to predict yield. - Corner Analysis: Simulate at fast/slow/typical process corners, voltage, and temperature (PVT) extremes. SPICE Models - BSIM (Berkeley Short-channel IGFET Model): Industry standard MOSFET model (BSIM3, BSIM4 for planar; BSIM-CMG for FinFET/GAA). - PSP: Compact MOSFET model used by some foundries. - Model Cards: Foundry-provided parameter files characterizing transistor behavior at each process corner. Contain hundreds of parameters. Modern SPICE Tools - Synopsys HSPICE: Gold-standard accuracy. Used for analog design signoff. - Synopsys PrimeSim: Next-generation SPICE with multi-threaded performance. - Cadence Spectre: Tightly integrated with Virtuoso analog design environment. - Cadence Spectre FX: Fast SPICE with parallelism for large digital blocks. - Siemens AFS: Analog FastSPICE for large mixed-signal verification. FastSPICE vs. SPICE - SPICE: Full accuracy, slow. Practical for circuits up to ~50K transistors. - FastSPICE: Approximations for 10-100× speedup. Handles millions of transistors. Used for full-chip power analysis, memory verification, and mixed-signal simulation.