Linear regulators are easy to implement and have better noise and drift characteristics than switching approaches. Their largest disadvantage is inefficiency: excess energy dissipated as heat. Several well-known techniques are available to minimize the input-to-output voltage across a linear regulator. I had been looking for an inexpensive, easy-to-implement, and efficient preregulator to reduce the dropout voltage of a linear regulator. Closed-loop, self-oscillating preregulators built around a switching transistor, a comparator, and a filter are difficult to predict in terms of frequency.