Power mosfet - power semiconductor devices , Electrical Engineering


MOSFET stands  for metal oxide semiconductor fields  effect transistor.  A power  MOSFET has  three  terminal  drain source  and  gate,. It  is unipolar device  means its operations  depends upon   the flow  of one  carriers  only. The power MOSFET is designed  to handle large amounts of power. Compared to the other power semiconductor  device s its  main advantages are high  commutation speed  and good efficiency at low voltages. Power MOSFET is a voltage controlled  device and it requires only small  input  current. It has extremely high input impedance  and is widely used in switching  devices. The  power MOSFET  is the most widely used low voltage  switch and  used in low power high frequency converters power suppliers DC to DC converters and low voltage motor controllers. MOSFET have a very thin silicon dioxide layer  is kept  very thin to ensure that the gate has  good control  over the  gate  current. This layer  could be  destroyed if a voltage  higher  than rated value is applied to the gate.

2055_Power MOSFET.PNG

                                                                         figure N - Channel V- MOSFET

Power MOSFET  are usually constructed in v shape as shown in  because  of its v shapes  sometimes it is called  the  v MOSFET  or V EFT. V shaped  cut penetrates from the  device  surface  almost  to the N  substrate through  N  P and N layers  as shown  in  the N  layers  are made  heavily doped low resistive material and the N layers is made  lightly doped  high resistance region.

1304_power MOSFET N channel P channel.PNG

                                                             Figure symbol of power MOSFET N channel P channel

The silicon dioxide dielectric  layer  covers both the  horizontal surface and v cut  surface. The  insulated gate is made by depositing a metal film on the silicon dioxide (Sio2) layer in the v cut. Source terminals are made by  making a contact to the upper N+ and P layers  through the layer. The  drain terminal is made  by N+ substrate of the device. The  power MOSFET is an enhancement  type MOSFET  and in this type of MOSFET  there is no channel exists  between drain  and source until the  gate is  positive with respect to the source. The  symbol of power MOSFET is shown  in this type of MOSFET  there is an enhancement type and source  until  the gate is positive  with respect to the source. The symbol of power  MOSFET.


Posted Date: 4/2/2013 3:59:15 AM | Location : United States

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