This paper presents the feedback linearization based control of DC/DC buck converter, the output voltage controlled. Also, the presence of parasitic elements are not studied in detail in a previous article, therefore the applied state space model are taking into account of those. The high slew rate of the controller cause inrush current during start-up, which have been examined and reduced. The linearized system has been investigated with linear quadratic regulator (LQR) through an example and simulated via Matlab.