Editing MOSFET (section)

=== Power MOSFET ===
[[file:Power mos cell layout.svg|thumb|upright=1.2|Cross section of a power MOSFET, with square cells. A typical transistor is constituted of several thousand cells.]]
{{Main|Power MOSFET}}

[[Power MOSFET]]s have a different structure.<ref>{{cite book|title=Power Semiconductor Devices|first=B. Jayant|last=Baliga|publisher=PWS publishing Company|location=Boston|isbn=978-0-534-94098-0|year=1996}}</ref> As with most power devices, the structure is vertical and not planar. Using a vertical structure, it is possible for the transistor to sustain both high blocking voltage and high current. The voltage rating of the transistor is a function of the doping and thickness of the N-[[epitaxial]] layer (see cross section), while the current rating is a function of the channel width (the wider the channel, the higher the current). In a planar structure, the current and breakdown voltage ratings are both a function of the channel dimensions (respectively width and length of the channel), resulting in inefficient use of the "silicon estate". With the vertical structure, the component area is roughly proportional to the current it can sustain, and the component thickness (actually the N-epitaxial layer thickness) is proportional to the breakdown voltage.<ref>{{cite web|url=http://www.element-14.com/community/docs/DOC-18273/l/power-mosfet-basics-understanding-mosfet-characteristics-associated-with-the-figure-of-merit|title=Power MOSFET Basics: Understanding MOSFET Characteristics Associated With The Figure of Merit|website=element14|accessdate=27 November 2010|archive-url=https://web.archive.org/web/20150405142659/http://www.element-14.com/community/docs/DOC-18273/l/power-mosfet-basics-understanding-mosfet-characteristics-associated-with-the-figure-of-merit |archive-date=5 April 2015 }}</ref>

Power MOSFETs with lateral structure are mainly used in high-end audio amplifiers and high-power PA systems. Their advantage is a better behaviour in the saturated region (corresponding to the linear region of a bipolar transistor) than the vertical MOSFETs. Vertical MOSFETs are designed for switching applications.<ref>{{cite web|url=http://www.element-14.com/community/docs/DOC-18275/l/power-mosfet-basics-understanding-gate-charge-and-using-it-to-assess-switching-performance|title=Power MOSFET Basics: Understanding Gate Charge and Using It To Assess Switching Performance|website=element14|accessdate=27 November 2010|archive-url=https://web.archive.org/web/20140630044120/http://www.element-14.com/community/docs/DOC-18275/l/power-mosfet-basics-understanding-gate-charge-and-using-it-to-assess-switching-performance |archive-date=30 June 2014 }}</ref>