Physically-based statistical analysis of nonlinear circuits through X-parameters

The active device X-parameters extracted from physics-based TCAD simulations are imported into the Keysight ADS environment following the techniques outlined in [1], leading to an efficient, yet physically sound, circuit-level nonlinear model, retaining a direct link with the device fabrication technology. In this work, the X parameter model is used to demonstrate that a fully statistical analysis of a nonlinear circuit as a function of technological spread of the active device can be efficiently carried out within ADS, with extremely reduced simulation time and excellent agreement with the original TCAD analysis. As a test case, we address the statistical analysis of a deep class AB amplifier as a function of the variations of both the active device doping and the circuit layout. The statistical distribution of the output power significantly depends on the power backoff and exhibits a marked skew, which cannot be fully addressed by standard sensitivity or linearized approaches. The effect of correlated or uncorrelated active device or layout variations is also investigated in a combined stage.