An introduction to Depletion-mode MOSFETs

Since the mid-nineteen seventies the “enhancement-mode” MOSFET has been the subject of almost continuous global research, development, and refinement by both the semiconductor industry and academia. As a result it has become the predominant MOSFET topology that encompasses discrete MOS power switches and CMOS. By contrast, the depletion-mode MOSFET has not received the same attention or popularity over this time, despite being the oldest member of the MOSFET family. It does have some rather unique characteristics though, which cannot be easily replicated by other means. This article will look at depletion mode MOSFET device structure, operation and applications to help designers further exploit some of the unique characteristics of these devices.