Diodes and transistors are nonlinear devices and the corresponding system of equations is more complicated. The conductance of a nonlinear device change with the change of the applied voltage (G*V=I). Given that any nonlinear function may be expressed as a series of linear approximations, the way around this problem is to break the nonlinear I-V relationships into several smaller linear approximations. The approximation precision increases with the increase of linear segments.

During the simulation the analog simulator transforms the nonlinear components into simple linear components, each one representing one linear approximation step. At each simulation step the linear equivalent circuit is used to represent the component as it is operating at that voltage bias.

The construction of a linear model of a diode in each operating point is known as linearization resulting in a linear diode model. Note that the model implies the use of current source.

During a simulation, the conductance Gd is stored in the conductance array, the equivalent Ieq is stored in current array. At each solution point these values are computed and stored in system matrix.