About MOSFET

1. WELCOME TO MY PRESENTATION
1

2. 2

3. Metal Oxide Semiconductor
FET(MOSFET)
3

4. 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).
4

5. MOSFET Structure
p-Si
n+
L
Source Gate Drain
Field Oxide
Gate Oxide
Bulk (Substrate)
5

6. Types of Field Effect Transistors
(The Classification)
JFET
MOSFET
n-Channel JFET
p-Channel JFET
n-Channel
EMOSFET
p-Channel
EMOSFET
Enhancement
MOSFET
Depletion
MOSFET
n-Channel
DMOSFET
p-Channel
DMOSFET
FET
6

7. 7

8. Depletion Type
•Channel region
is already
diffused
between the
Drain and Source
• Deplete, or
“pinch-off” the
Channe
8

9. Depletion MOSFET
9

10. Basic Operation
Before After
10

11. 11

12. 12

13. 13

14. • n-Channel MOSFET
Schematic symbol
Depletion MOSFET
14

15. • p-Channel MOSFET Schematic symbol
Depletion MOSFET
15

16. Depletion MOSFET Bias
• Gate bias
• Self bias
• voltage-divider bias
• Zero bias
16

17. Self Bias
Some formula :
Self-biased configuration results in VGS=-IDRS 17

18. Voltage-divider bias
Some formula :
 2
)(
)(
TonGS
onD
VV
I
k

VGS>VT, ID=k(VGS-VT)2
18

19. 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
19

20. Enhancement Type
• No channel region
exists between the
Drain and Source
• “Invert” the region
between the Drain
and Source to
induce a channel
20

21. Enhancement MOSFET
21

22. • p-Channel MOSFET
• Construction is reverse of n-channel DMOSFET.
Enhancement MOSFET
Schematic symbol
22

23. Enhancement MOSFET Bias
• Gate bias
• Voltage-divider bias
• Drain-feedback bias
23

24. E-MOSFET Voltage-Divider Biasing
• VGS=VG-IDRS
• Where VG=R2xVDD/(R1+R2)
• VDS=VDD-ID(RS+RD)  2
)(
)(
TonGS
onD
VV
I
k


24

25. 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 25

26. 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
26

27. Applications of MOSFET
27

28. 28

29. 29

30. 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
30

31. THANKS TO ALL!!!
???
31