electricalandelectronics.org » Enhancement type MOSFET

Characteristics of Enhancement Type MOSFET

arjun — Thu, 16 Oct 2008 19:13:18 +0000

The drain characteristics of enhancement type MOSFET is given below.This depicts the variation of drain current(ID)with drain to source voltage(VDS)for different values of gate to source voltage(VGS). The lower most curve is for VGS(Th).When VGS < VGS(Th)drain current is almost zero.When VGS >VGS(Th) the device is ON.As in the case of other FET,the device can operate in the ohmic,active or cutoff(break down)region.The rising part of curve (fromVDS=0 to VDS=few volts)is the ohmic region.The device behaves as a resistor,when operated in this region.The drain current is almost constant when the device operates in the active region.when VDS exceeds the rated value,avalanche breakdown occurs and the device is in the breakdown region. Transconductance curve of enhancement MOSFET is read more

Enhancement Type Power MOSFET

arjun — Tue, 30 Sep 2008 17:55:42 +0000

This type of power MOSFET is widely used in digital computers. The construction of enhancement type power MOSFET is shown in figure above .This is an n-channel device.However as seen in the figure,the p-substrate extends right up to the silicon dioxide layer.Thus there is no n-channel between drain and source. The above figure shows the connections.When the gate voltage is zero,drain battery tries to push free electrons from the source to the drain.However the p-substrate has only a few thermally produced free electrons and some electrons due to surface leakage.Therefore the drain current is almost zero.When gate is positive(VGS>0)the gate attracts free electrons into the p-substrate region these free electrons recombine with holes near silicon dioxide layer.When VGS is large read more