Some general properties and limits of regulator technology are examined independent of circuit topology or device physics. As foundation, the work of Moore and Wilson on DC-DC conversion circuits is used. Their work showed the need for some intermediate DC-AC inversion in the converter. These findings are extended and applied to a dc-dc regulator, defined as a special network deriving all its power from a bulk source and supplying regulated DC to a load. It is subject to changes in environment bulk voltage fluctuations, load changes, etc. A dc-dc regulation can be performed with maximum efficiency and without circuit redundancy by two classes of regulators. They are the modulated source and modulated transmission regulators. The operating frequency of the modulated source regulator is established via sampled-data theory. A similar constraint on the modulated transmission regulator is governed indirectly, by the Manley-Rowe type power gain relationship.