About MOSFET
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Transcript of About MOSFET
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MOSFET
• A field effect transistor (FET) that can be operated in the enhancement-mode is called a MOSFET.
• There are 4 terminals : source (S), gate (G) and drain (D), Substrate (SS).
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Types of Field Effect Transistors (The Classification)
JFET
MOSFET
n-Channel JFETp-Channel JFET
n-Channel EMOSFET
p-Channel EMOSFET
Enhancement MOSFET
Depletion MOSFET
n-Channel DMOSFET
p-Channel DMOSFET
FET
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Depletion Type•Channel region is
already diffused between the Drain and Source•Deplete, or
“pinch-off” the Channe
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Enhancement MOSFET• Primary difference
between depletion-type and enhancement-type is the absence of channel between Source and Drain terminals.
N-channel enhancement-type MOSFET
Schematic symbol
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Enhancement Type
•No channel region exists between the Drain and Source• “Invert” the region
between the Drain and Source to induce a channel
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• p-Channel MOSFET• Construction is reverse of n-channel DMOSFET.
Enhancement MOSFETSchematic symbol
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E-MOSFET Voltage-Divider Biasing
• VGS=VG-IDRS
• Where VG=R2xVDD/(R1+R2)
• VDS=VDD-ID(RS+RD) 2)(
)(
TonGS
onD
VVI
k
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E-MOSFET Feedback Biasing
IG=0 V, VD=VG, VDS=VGS, VDS=VDD-IDRD, VGS=VDD-IDRD
When ID=0 A:VGS=VDD
When VGS=0 V:ID=VDD/RD
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Applications of MOSFET
• Digital integrated circuits such as microprocessors and memory devices contain thousands to millions of integrated MOSFET
• logic gates and data storage• Switch mode power supplies, • Variable frequency drives • Radio systems use MOSFETs as oscillators, or mixers to
convert frequencies. • Sound reinforcement and • Automobile sound systems
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JEFT vs MOSFET JEFT MOSFET
1. High input impedance 1. Very high input impedance
2. It can be operated only in depletion mode.
2. It can be operated both depletion and enhancement mode.
3. High gate current 3. Low gate current
4. High drain resistance 4. Low drain resistance
5. Conductivity is controlled by the reverse biasing of the gate
5. Conductivity is controlled by the carriers induced in the channel
6. Schematic symbol 6. Schematic symbol
7.Transconductance curve 7.Transconductance curve