An efficient transistor-level piecewise-linear macromodeling approach for model order reduction of nonlinear circuits

Trajectory piecewise-linear macromodeling (TPWL) technique has been widely employed to characterize strong nonlinear circuits, and makes the reduction of the strong nonlinear circuits possible. The trajectory piecewise-linear macromodeling technique linearizes nonlinear circuits around multiple expansion points which are extracted from state trajectories driven by training inputs. However, the accuracy of the trajectory piecewise-linear macromodeling technique heavily relies on the extracted expansion points and the training inputs. It will lead to large error in simulation if state vector reaches regions far away from the extracted expansion points. In this paper, we propose an efficient transistor-level piecewise linearization scheme for macromodeling of nonlinear circuits. Piecewise linear models are first built for each transistor. The macromodel of the whole nonlinear circuit is then constructed by combining all the piecewise-linear models of the transistors together with appropriate weight functions. The proposed approach can cover remarkably larger state space than the TPWL method. By using the complete piecewise-linear models of the transistors, the constructed piecewise-linear models of the nonlinear circuits are capable of covering the whole state space of the nonlinear circuits. More importantly, model order reduction of the proposed transistor-level piecewise linearization macromodel is also possible, which makes the proposed method a potentially good macromodeling approach for model order reduction of nonlinear circuits.