  On the base of a 1D Shr\"{o}dinger equation the non-linear first-order
differential equation (Ricatti type) for a quantum wave impedance function was
derived. The advantages of this approach were discussed and demonstrated for a
case of a single rectangular barrier. Both the scattering and the bound states
problem were reformulated in terms of a quantum wave impedance and its
application for solving both these problems was considered. The expressions for
a reflection and a transmission coefficient were found on the base of a quantum
wave impedance approach.
