Implications
Device model equations must be continuous with continuous derivatives and derivative calculation must be accurate derivative of function (not all models do this - Poor diode models and breakdown models don’t - be sure models are decent - beware of user-supplied models)
Watch out for floating nodes (If a node becomes disconnected, then J(x) is singular)
Give good initial guess for x(0)
Most model computations produce errors in function values and derivatives. Want to have convergence criteria || x(k+1) - x(k) || < ? such that ? > than model errors.