Cascode MOSFET increases boost regulator's input- and output-voltage ranges.

This paper addresses the limitations of integrated circuit boost regulators. One can extend a boost regulator's output-voltage range by adding an external transistor that has been a higher breakdown voltage than the regulator. However, the internal design of a typical boost regulator's control circuitry often prevents direct drive of an external transistor's base or gate. As an alternative, one can add an external higher voltage transistor by connecting it in a cascode configuration. Most boost regulators feature a peak-current-control method that reduces the number of external components and thus shrinks the overall printed circuit-board area of the converter circuit. One can add a higher voltage metal oxide field-effect transistor (MOSFET) for applications that require an output voltage higher than the internal transistor's breakdown voltage. The cascode circuit also can produce any output voltage that is within the drain-to-source breakdown-voltage rating of MOSFET.