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ORIENTAL INSTITUTE OF
SCIENCE & TECHNOLOGY
Submitted To:-
Abhilasha Mam
Submitted By :-
1.Pawan Jha
2.Rishabh Tripathi
3.S...
ACKNOWLEDGEMENT
 
It is with great reverence that we
express out gratitude to our guide ,Hon’ble “Miss Abhilasha
Verma “ D...
FET ( Field Effect Transistor)
INTRODUCTION:--
The field-effect transistor (FET) is a transistor that uses an
electric fie...
SOME BASIC INFORMATION
ABOUT FET
• FETs can be majority-charge-carrier devices, in
which the current is carried predominan...
• The conductivity of the channel is a function of the potential
applied across the gate and source terminals.
The FET's t...
ABOUT THE TERMINALS OF
FET
• All FETs have source, drain, and gate terminals that correspond
roughly to the emitter, colle...
Types of Field Effect Transistors
(The Classification)
» JFET
MOSFET (IGFET)
n-Channel JFET
p-Channel JFET
n-Channel
EMOSF...
Gate
Drain
Source
SYMBOLS
n-channel JFET
Gate
Drain
Source
n-channel JFET
Offset-gate symbol
Gate
Drain
Source
p-channel J...
P P +
-
DC Voltage Source
+
-
+
-
N
N
Operation of a JFET
Gate
Drain
Source
Operation of Junction Field Effect Transistor (JFET)
• When neither any bias is applied to the gate (i.e. when VGS =
0) no...
• The gate is more “negative” with respect to those points in the
channel which are nearer to D than to S. Hence, depletio...
MOSFET
• The metal–oxide–semiconductor field-effect transistor
(MOSFET, MOS-FET, or MOS FET) is a transistor used for
ampl...
• the body (or substrate) of the MOSFET often is connected to
the source terminal, making it a three-terminal device like ...
Figure p-Channel FET circuit symbols. These are the same as the circuit symbols for n-channel devices,
except for the dire...
Few important advantages of FET over
conventional Transistor
● Unipolar device i.e. operation depends on
only one type of ...
ADVANTAGES CONTD…
● Low Voltage Low Current Operation is possible
(Low-power consumption)
● Less Noisy as Compared to BJT
...
Disadvantages of FET
• It has a relatively low gain-bandwidth product compared to a
BJT. The MOSFET has a drawback of bein...
Uses of FET
• The most commonly used FET is the MOSFET. The CMOS
(complementary metal oxide semiconductor) process technol...
• A common use of the FET is as an amplifier. For
example, due to its large input resistance and low
output resistance, it...
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Ppt presentation on  FET
Ppt presentation on  FET
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Ppt presentation on FET

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Ppt presentation on FET

  1. 1. ORIENTAL INSTITUTE OF SCIENCE & TECHNOLOGY Submitted To:- Abhilasha Mam Submitted By :- 1.Pawan Jha 2.Rishabh Tripathi 3.Sanjeev Mandal 4.Saurabh Singh 5.Shubham kumar
  2. 2. ACKNOWLEDGEMENT   It is with great reverence that we express out gratitude to our guide ,Hon’ble “Miss Abhilasha Verma “ Department of Electronics & communication , Oriental institute of science & technology Bhopal(M.P.) for her precious guidance and help in this project work . The credit for a successful completion of this project goes to our keen interest, timing, guidance and valuable suggestion otherwise our endeavwould have been futile .
  3. 3. FET ( Field Effect Transistor) INTRODUCTION:-- The field-effect transistor (FET) is a transistor that uses an electric field to control the shape and hence the conductivity of a channel of one type of charge carrier in a semiconductor material. FETs are unipolar transistors as they involve single-carrier-type operation. The concept of the FET predates the bipolar junction transistor (BJT), though it was not physically implemented until after BJTs due to the limitations of semiconductor materials and the relative ease of manufacturing BJTs compared to FETs at the time.
  4. 4. SOME BASIC INFORMATION ABOUT FET • FETs can be majority-charge-carrier devices, in which the current is carried predominantly by majority carriers, or minority-charge-carrier devices, in which the current is mainly due to a flow of minority carriers. • The device consists of an active channel through which charge carriers, electrons or holes, flow from the source to the drain. Source and drain terminal conductors are connected to the semiconductor through ohmic contacts.
  5. 5. • The conductivity of the channel is a function of the potential applied across the gate and source terminals. The FET's three terminals are: • Source (S), through which the carriers enter the channel. Conventionally, current entering the channel at S is designated by IS. • Drain (D), through which the carriers leave the channel. Conventionally, current entering the channel at D is designated by ID. Drain-to-source voltage is VDS. • Gate (G), the terminal that modulates the channel conductivity. By applying voltage to G, one can control ID.
  6. 6. ABOUT THE TERMINALS OF FET • All FETs have source, drain, and gate terminals that correspond roughly to the emitter, collector, and base of BJTs. Most FETs have a fourth terminal called the body, base, bulk, or substrate. • This fourth terminal serves to bias the transistor into operation; it is rare to make non-trivial use of the body terminal in circuit designs, but its presence is important when setting up the physical layout of an integrated circuit. • The size of the gate, length L in the diagram, is the distance between source and drain. The width is the extension of the transistor, in the direction perpendicular to the cross section in the diagram. • Typically the width is much larger than the length of the gate. A gate length of 1 µm limits the upper frequency to about 5 GHz, 0.2 µm to about 30 GHz.
  7. 7. Types of Field Effect Transistors (The Classification) » JFET MOSFET (IGFET) n-Channel JFET p-Channel JFET n-Channel EMOSFET p-Channel EMOSFET Enhancement MOSFET Depletion MOSFET n-Channel DMOSFET p-Channel DMOSFET FET
  8. 8. Gate Drain Source SYMBOLS n-channel JFET Gate Drain Source n-channel JFET Offset-gate symbol Gate Drain Source p-channel JFET
  9. 9. P P + - DC Voltage Source + - + - N N Operation of a JFET Gate Drain Source
  10. 10. Operation of Junction Field Effect Transistor (JFET) • When neither any bias is applied to the gate (i.e. when VGS = 0) nor any voltage to the drain w.r.t. source (i.e. when VDS = 0), the depletion regions around the P-N junctions , are of equal thickness and symmetrical. • 2. When positive voltage is applied to the drain terminal D w.r.t. source terminal S without connecting gate terminal G to supply, as illustrated in fig. 9.4, the electrons (which are the majority carriers) flow from terminal S to terminal D whereas conventional drain current ID flows through the channel from D to S. Due to flow of this current, there is uniform voltage drop across the channel resistance as we move from terminal D to terminal S. This voltage drop reverse biases the diode.
  11. 11. • The gate is more “negative” with respect to those points in the channel which are nearer to D than to S. Hence, depletion layers penetrate more deeply into the channel at points lying closer to D than to S. Thus wedge-shaped depletion regions are formed, as shown in figure. when Vds is applied. The size of the depletion layer formed determines- the width of the channel and hence the magnitude of current ID flowing through the channel.
  12. 12. MOSFET • The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a transistor used for amplifying or switching electronic signals. Although the MOSFET is a four-terminal device with source (S), gate (G), drain (D), and body (B) terminals.
  13. 13. • the body (or substrate) of the MOSFET often is connected to the source terminal, making it a three-terminal device like other field-effect transistors. • Because these two terminals are normally connected to each other (short-circuited) internally, only three terminals appear in electrical diagrams. The MOSFET is by far the most common transistor in both digital and analog circuits, though the bipolar junction transistor was at one time much more common.
  14. 14. Figure p-Channel FET circuit symbols. These are the same as the circuit symbols for n-channel devices, except for the directions of the arrowheads.
  15. 15. Few important advantages of FET over conventional Transistor ● Unipolar device i.e. operation depends on only one type of charge carriers (h or e) ● Voltage controlled Device (gate voltage controls drain current) ● Very high input impedance (≈109 -1012 Ω) ● Source and drain are interchangeable in most ● Low-frequency applications
  16. 16. ADVANTAGES CONTD… ● Low Voltage Low Current Operation is possible (Low-power consumption) ● Less Noisy as Compared to BJT ● No minority carrier storage (Turn off is faster) ● Self limiting device ● Very small in size, occupies very small space in Ics ● Low voltage low current operation is possible in MOSFETS ● Zero temperature drift of out put is possible
  17. 17. Disadvantages of FET • It has a relatively low gain-bandwidth product compared to a BJT. The MOSFET has a drawback of being very susceptible to overload voltages, thus requiring special handling during installation. • The fragile insulating layer of the MOSFET between the gate and channel makes it vulnerable to electrostatic damage during handling. This is not usually a problem after the device has been installed in a properly designed circuit.
  18. 18. Uses of FET • The most commonly used FET is the MOSFET. The CMOS (complementary metal oxide semiconductor) process technology is the basis for modern digital integrated circuits. This processtechnology uses an arrangement where the (usually "enhancement-mode") p-channel MOSFET and n-channel MOSFET are connected in series such that when one is on, the other is off. • In FETs, electrons can flow in either direction through the channel when operated in the linear mode. The naming convention of drain terminal and source terminal is somewhat arbitrary, as the devices are typically (but not always) built symmetrically from source to drain. This makes FETs suitable for switching analog signals between paths (multiplexing). With this concept, one can construct a solid-state mixing board, for example.
  19. 19. • A common use of the FET is as an amplifier. For example, due to its large input resistance and low output resistance, it is effective as a buffer in common- drain (source follower) configuration

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