Metal Oxide Semiconductor Field Effect Transistor: Difference between revisions

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imported>John R. Brews
(bulk → body, the common terminology)
imported>John R. Brews
(Redirect to Metal-oxide-semiconductor field-effect transistor)
 
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#REDIRECT [[Metal-oxide-semiconductor field-effect transistor]]
 
The '''Metal Oxide Semi-conductor Field Effect Transistor''' (MOSFET) is a type of [[Field Effect Transistor|FET]] that consists of three layers: [[semi-conductor]] (called ''body''), oxide (working as insulator) and metal top electrode (conductor, called ''gate'').
 
There are four contacts altogether: in addition to the gate and body contacts already descirbed, there are two contacts atop the body at opposite sides of the gate called ''source'' and ''drain''. Because the transistor is symmetrical, they can swap their functions. They do not permit current flow to the body in normal operation, as they form reverse biased diodes with the body. They do allow current between source and drain upon formation (by the gate) of a surface ''channel'' at the top surface of the body, next to the insulator.  The channel conductivity depends upon the voltage difference between the gate and body (''V<sub>gb</sub>''). The amount of current drawn in the channel depends upon the voltage drop across it, the drain to source voltage (''V<sub>ds</sub>''). The channel strength also is affected by so-called "back gate bias", that is, by the body to source voltage (''V<sub>bs</sub>'').
 
The control of the channel by the gate is similar to the formation of an ''inversion layer'' in the [[Metal Oxide Semi-conductor Capacitor|MOS Capacitor]], which is only a two-terminal device (gate and body contacts).

Latest revision as of 11:06, 16 January 2011

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