NEMESIS: NEtlist-Driven Modeling and Equation Synthesis with Inversion-Aware SPICE Anchoring

2026-07-06

AI Summary

This work addresses the longstanding challenge in operational transconductance amplifier (OTA) design of balancing rapid analytical modeling with the high accuracy of SPICE simulation. To this end, the authors propose NEMESIS, a novel framework that uniquely integrates multimodal large language models with closed-loop SPICE simulation. By leveraging circuit primitive recognition, structure-aware automatic generation of analytical equations, and an inversion-aware mechanism, NEMESIS achieves highly efficient and accurate modeling across five OTA topologies using a 65 nm PDK. The method incorporates a SPICE-anchored refinement loop, yielding an average relative error below 7% while accelerating post-convergence evaluation by approximately 4,622× compared to full SPICE simulation.

Abstract

This work presents NEMESIS, a multimodal framework for operational transconductance amplifier (OTA) design using large language models (LLMs). NEMESIS strikes a balance between fast, approximate analytical models vs. accurate, computationally expensive SPICE evaluations. Given an OTA netlist and schematic, NEMESIS first identifies circuit primitives and then generates progressively more accurate performance equations. The framework begins with equations retrieved from the prior invocations of NEMESIS to structurally similar OTAs, if available; otherwise, it uses the LLM to derive the initial equations directly from the circuit input. These equations are iteratively refined via a SPICE-based repair loop. In a commercial 65nm PDK, NEMESIS is demonstrated on five OTA topologies, producing SPICE-verified equations across biasing ranges with <7% average relative error and a post-convergence evaluation speedup of ~4622x over full SPICE-based evaluation.

Problem

• operational transconductance amplifier
• SPICE simulation
• analytical modeling
• performance equations
• circuit design

Innovation

• large language models
• SPICE anchoring
• equation synthesis
• netlist-driven modeling
• operational transconductance amplifier