Types of MOSFETs
ECE 2204
Types of MOSFETS
n-channel
Enhancement Mode
(nMOSFET)
p-channel
Enhancement Mode
(pMOSFET)
n-channel
Depletion Mode
(nMOSFET)
p-channel
Depletion Mode
(pMOSFET)
MOSFETs
Enhancement mode
Depletion mode
• Also known as Normally Off
transistors.
▫ A voltage must be applied to
the gate of the transistor, at
least equal to the threshold
voltage, to create a
conduction path between
the source and the drain of
the transistor before current
can flow between the source
and drain.
• Also known as Normally On
transistors.
▫ A voltage must be applied to
the gate of the transistor, at
least equal to the threshold
voltage, to destroy a
conduction path between
the source and the drain of
the transistor to prevent
current from flowing
between the source and
drain.
Cross-Sectional View of n channel
Enhancement Mode Transistor
oxide
Before electron
inversion layer is
formed
After electron
inversion layer is
formed
p channel Enhancement Mode
Transistor
n channel Depletion Mode Transistor
p channel Depletion Mode Transistor
Symbols for n channel Enhancement
Mode MOSFET
VGS ≥ 0V, VDS ≥ 0V
VTN is positive
Symbols for p channel Enhancement
Mode MOSFET
VGS ≤ 0V, VDS ≤ 0V
VTP is negative
Symbols for n channel
Depletion Mode MOSFET
Symbols for p channel
Depletion Mode MOSFET
PSpice MOSFET Symbols
• The IRF150 is an nMOS and the IRF9140 is a pMOS.
Both are enhancement mode transistors.
▫ The body terminal is connected to the source terminal on
the FET.
▫ “M” is used to denote that the device is a MOSFET.
Family of iD Versus vDS Curves:
Enhancement-Mode nMOSFET
Triode/
Nonsaturation
VDS ≤ VGS – VTN
VDS ≥ VGS – VTN
Pinch-off/Saturation
Family of iD Versus vDS Curves:
Depletion-Mode nMOSFET
Assuming that VTN < -1V
For this course
• I am going to emphasize the operation and
applications of Enhancement Mode FETs