The document discusses MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors). It describes MOSFETs as four-terminal devices made of metal, oxide, and semiconductor materials. The document outlines the two main types of MOSFETs - depletion-enhancement MOSFETs (DE-MOSFETs) and enhancement-only MOSFETs (E-Only MOSFETs) - and explains their constructions, working principles, and characteristics like transfer and drain curves. Applications of MOSFETs include use in switching circuits, amplifiers, inverters, and power supplies.

2. Topic:-
MOSFET
Nimra
Shahbaz
Akram
M. Abdullah
Presented
by:- Asif ali
Hasnat
Afraz Abbasi

3. FET:-
Definition:-
FET stands for Field Effect Transistor
It is a three-terminal unipolar solid-state
device
It is an electronic device in which current is
controlled by an electric field

4. Types of FET:-
There are two types of FETs:-
1.Junction Field Effect Transistor
(JFET)
2.Metal-Oxide Semiconductor Field
Effect Transistor (MOSFET)

5. MOSFET:-
Abbreviation:-
MOSFET stands for Metal Oxide Semiconductor Field Effect Transistor.
Definition:-
The MOSFET is core of integrated circuit.
 It is designed and fabricated in a single chip because of very small
size.
2nd Name:-
It is also known as Insulated-Gate FET (IGFET).

7. Types of
MOSFET:-There are two types of MOSFET:-
1.Depletion-Enhancement MOSFFET (DE-
MOSFET).
2.Enhancement-only MOSFET (E-Only
MOSFET).
Both of these can be either P-Channel or N-

8. Construction of
MOSFET:-
The MOSFET is a four terminal device with Source(S), Gate(G),
Drain(D), and Body(B) terminals.
The body of the MOSFET is connected to the source terminal so
making it a three terminal device.
There is one layer of Silicon dioxide (SiO2) .
There are two highly doped regions and one lightly doped region
depending upon the Channel.

10. Working of
MOSFET:-
It works by electronically varying the width of a channel
along which charge carriers (electrons or holes) flow.
The wider the channel, the better the device conducts.
The charge carriers enter the channel at source and
exit via drain.
The width of the channel is controlled by the voltage on
an electrode called Gate which is located between
Source and Drain.

11. DE-MOSFET:-
Abbreviation:-
DE-MOSFET stands for Depletion-Enhancement Metal
Oxide Semiconductor Field Effect Transistor.
It operates in two modes:-
Depletion mode
Enhancement mode

12. Modes of DE-
MOSFET:-
Depletion mode:-
When negative gate to source voltage is applied, the DE-
MOSFET operates in depletion mode.
Enhancement mode:-
When positive gate to source voltage is applied, the DE-
MOSFET operates in enhancement mode.

13. construction of
DE-MOSFET:-
It has Source, Drain, Gate and a Substrate.
It’s Gate is insulated from it’s conducting channel
by an ultra thin metal oxide insulating film (usually
Silicon Dioxide SiO2).
Gate voltage controls Drain voltage.
DE-MOSFET has only one P-region or N-region
called substrate.

14. Types of DE-
MOSFET:-
There are two types of DE-MOSFET:-
1.N-channel DE-MOSFET.
2.P-channel DE-MOSFET.
Both P-channel and N-channel operate in two
modes i.e; Depletion and Enhancement
mode.

15. Construction Diagrams of
P and N-Channel DE-
MOSFET:-

16. Working of N-
Channel DE-
MOSFET:-Depletion mode of N-Channel DE-
MOSFET:-
When VGS=0, electrons can flow freely from source to drain
through the conducting channel which exists between them.
When gate is given negative voltage, it depletes the N-channel
of it’s electrons by inducing positive charge in it.
Greater the negative voltage on the gate, greater the reduction

17. Working of N-
Channel DE-
MOSFET:-Depletion mode of N-Channel DE-MOSFET:-
In fact, too much negative voltage called VGS(off) can
cut off the channel.
Hence, with negative gate voltage, a DE-MOSFET
behaves like JFET.
Negative-gate operation of DE-MOSFET is called
it’s depletion mode operation.

19. Working of N-
Channel DE-
MOSFET:-Enhancement mode of N-Channel DE-MOSFET:-
 When positive voltage is applied to the Gate, the input Gate Capacitor is
able to create free electrons in the channel which increases ID.
Increased number of electrons increases or enhances the conductivity of
the channel.
Hence, conductivity of source to drain channel is increased that increases
the amount of current flows between terminals.
That’s why positive Gate operation of DE-MOSFET is known as
Enhancement mode operation.

21. Schematic symbols
of DE-MOSFET:-
When SS is connected
to an external load, we
have a 4 terminal
device.
When SS is internally
shorted to Source S, we
get a 3 terminal device.

22. Static characteristics
of N-Channel DE-
MOSFET:-VGS represents the Gate to Source voltage.
For a given VDS, ID flows even when VGS=0.
Keeping VDS constant, as VGS is made more negative, ID
keep decreasing till it becomes zero at VGS=VGS(off).
When used in Enhancement mode, ID increases as VDS
increased positively.

23. Drain Characteristics
of N-Channel DE-
MOSFET:-The upper curve for positive VGS, the lower curve for
negative VGS, and the bottom drain curve is for
VGS=VGS(OFF).
Depletion mode MOSFET is also known as Normally-ON
device.
When VGS becomes positive, IDS will increase following the
square law:-

25. Regions of Drain
Characteristics of N-Channel
DE-MOSFET:-
The drain curves display three regions i.e; Ohmic region, cut-off region and saturation region.
Cut-off region:-
VGS<VTH
ID=0, VGS=VGS(OFF)
Ohmic region:-
VGS>VTH
VDS<VGS-VTH
Saturation region:-
VGS>VTH
VDS>VGS-VTH
Threshold Voltage:-
Threshold voltage is
the voltage applied between
Gate and Source of a MOSFET
that is needed to turn the device
on for linear and saturation
regions of operation.

27. Transfer Characteristics
of N-Channel DE-
MOSFET:-
It is the graph plot between output current ID and
input voltage VGS for fixed VDS.
When VGS is negative, ID keep decreasing
(depletion mode).
When VGS is positive, ID increases rapidly
(enhancement mode).

29. E-Only MOSFET:-
Abbreviation:-
E-Only MOSFET stands for Enhancement-Only Metal Oxide
Semiconductor Field Effect Transistor.
Main Points:-
Enhancement mode MOSFET are the common switching element in
MOS. These devices are off at zero Gate-Source Voltage.
When there is no voltage on the Gate, the device does not conduct.
More is the voltage on Gate, the better the device will conduct.

30. Construction of E-
Only MOSFET:-
It differs in construction from the DE-
MOSFET because there is no channel
between Drain and Source.
It has three terminals Source, Drain and
Gate.
Gate voltage controls the Drain current.

31. Types of E-Only
MOSFET:-
There are two types of E-Only
MOSFET:-
1.N-Channel E-Only MOSFET.
2.P-Channel E-Only MOSFET.

32. Construction Diagrams of P
and N-Channel E-Only
MOSFET:-•

33. Symbols of P and N-
Channel E-Only
MOSFET:-

34. Working of N-
Channel E-Only
MOSFET:-When the Gate Voltage is zero, the current between Source and
Drain is zero.
The only way to get current is Positive Gate-Source voltages.
When Gate voltages are enough positive then the holes that are
touching the Silicon dioxide are filled and free electrons began to flow
from Source to Drain.
It creates thin layer of N-Type material next to Silicon Dioxide (SiO2)
called N-Type inversion layer.
Due to inversion layer, free electrons can flow easily from Source to
Drain.

35. Working of N-
Channel E-Only
MOSFET:-The minimum Vgs that creates the N-Type
inversion layer is called the Threshold Voltages,
symbolically VGS(th).
When VGS<VGS(th), the Drain current is zero.
When VGS>VGS(th), due to N-Type inversion layer,
the electrons will flow from S to D and current will
flow from D.

37. Drain curves of N-
Channel E-Only
MOSFET:-Vertical part of graph is ohmic region.
Horizontal part is active region.
When biased in ohmic region, it is equivalent to a
transistor.
When biased in active region, it is equivalent to
current source.
All above which we have discussed is active region.

39. Ohmic region:-
Although the E-MOSFET can be biased in the active region. This is
seldom done because it is primarily a switching device. The input
voltage is either low or high. Low voltage is 0 and Vgs(on) is high
voltage.
When it is biased in ohmic region, it is equivalent to a resistance of
Rds(on).
There is test point in the ohmic region for equation Vgs=Vgs(on).
Id(on) and Vds(on) are measured at Q test point.
By this we can evaluate the value of Rds(on) using the formula:-

40. Working of P-
Channel E-Only
MOSFET:-It is also known as P-MOS.
It is same as N-MOS but by changing polarities.
It is opposite to N-Channel E-Only MOSFET.
P-Channel E-Only MOSFETs are designed for negative
supply and outflowing negative Drain current.
The P-Channel MOSFET has a P-Channel region between
source and drain.

41. Working of P-
Channel E-Only
MOSFET:-It is 4 terminal device such as Gate, Drain, Source and
Body.
The Drain and Source are heavily doped.
Body of the substrate is N-Type.
The flow of current is due to the positively charged holes as
holes are majority carriers in P-Type.
When we apply negative Gate voltage, the electrons
present under the oxide layer are pushed downward into the

42. Working of P-
Channel E-Only
MOSFET:-The depletion region populated by the bound positive charges which
are associated with donor atom.
The negative Gate voltages also attract holes from positive source
and drain region into the channel region.
Also inversion region is formed.
When VGS=0, the current will not flow from Source to Drain.
When VGS>0, the current will not flow.
The current will only flow when VGS<0.

44. Drain curves of P-
Channel E-Only
MOSFET:-The drain curve graph for P-Channel is below:-
So this plot is just rotated 180 degree of N-Channel plot.

45. Table of E-Only
MOSFET:-
MOSFET
TYPE
VGS=+ve VGS=0 VGS=-ve
N-channel E-
MOSFET
ON OFF OFF
P-channel E-
MOSFET
OFF OFF ON

46. Advantages of
MOSFETThey can be operated in either enhancement mode or depletion
mode.
They have much higher input impedance as compared to JFET.
They have high drain resistance due to lower resistance of
channel.
They are easy to manufacture.
They support high speed of operation as compared to JFET’S.
MOSFET provide greater efficiency while operating at lower

47. Disadvantages of
MOSFET
In MOSFET , the layer between Gate and Channel is very Fragile
which is vulnerable to Electrostatic damage during Installation. It
requires well designed circuit to avoid the Issue.
MOSFET is very susceptible to overload voltages, hence special is
required during Installation.
 Its handling is not easy.

48. Applications of
MOSFETs:-
MOSFET is used for switching and amplifying
electronic signals in electronic devices.
It is used as an inverter.
It can be used in digital circuits.
MOSFET can be used as a high frequency
amplifier.

49. Applications of
MOSFETs:-
It can be used as a passive element e.g;
resistor, capacitor and inductor.
It can be used in brushless DC motor drive.
It can be used in electronic DC relay.
It is used in Switch Mode Power Supply
(SMPS).