An Op-Ed On Op-Amp Modeling

Op-amp circuits have long been a cornerstone of electronics, offering an elegant and versatile approach to feedback. For many, the ability to visualize circuit behavior through simulation is a powerful tool for exploring feedback concepts and refining op-amp circuit intuition. However, there's a frustrating irony in simulating op-amp circuits: while IC designers rely on SPICE for transistor-level design, using SPICE to simulate op-amps in larger application circuits often proves challenging. This article aims to address and solve this problem once and for all.

SPICE excels at simulating transistor-level details, yet lacks native circuit elements that emulate op-amp behavior accurately. This disconnect creates complications in modeling op-amps, leading to models that are either too simplified or overly complex. The IC manufacturers’ focus on showcasing product differentiation—such as lower offset voltages and higher power supply rejection ratios (PSRR)—further complicates the issue, often resulting in models that don't accurately reflect real-world performance. To bridge this gap, the new QSPICE native circuit element offers a streamlined solution for op-amp modeling, balancing simplicity with comprehensive functionality to enhance design accuracy and efficiency.