Differential Algebraic Systems with Properly Stated Leading Term and MNA Equations

Differential algebraic equations with properly stated leading term are equations of the form A(x(t),t)(d(x(t),t))'+b(x(t),t)=0 with in some sense well-matched coefficients. Systems resulting from the modified nodal analysis (MNA) in circuit simulation promptly fit into this form. Recent results concerning solvability and numerical treatment of those equations are discussed. An index notion that works via linearization is given. This allows for index criteria just in terms of the coefficients A,d,b and their first partial derivatives, no further derivative arrays are used