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.