In this paper we consider linear and nonlinear dynamic systems which are stabilizable via output feedback. In general, e.g. when the output feedback control law is carried out by zero insertion, such feedback is not physically realizable. It is shown that the insertion of some high frequency poles, which play the role of reduced order observer for the estimation of the output time derivatives, guarantees: (i) the physical realizability of the control law, and (ii) the fulfilment of the required stability properties.