A synthesis procedure for dynamic compensators based on a differential operator representation is developed. The compensators satisfy the algebraic separation, principle and may qualify as 'control observers'. As such they show the same properties as a state observer in a control loop. However, this compensator approach is more general, in that it immediately allows zero placement to be taken into account. For single-input, multi-output systems, a simple and unified procedure, for the construction of minimal order compensators with and without arbitrary pole placement is established. This procedure then is generalized in a straightforward way to the construction of low order compensators for multi-input systems. The approach is particularly advantageous if a higher order (dynamic) state feedback control law is given. In this case, a total compensator of minimal order can be constructed.