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=Field Effect Transistor=
==Basic information==
[[File:FET99.jpg|thumb|FET]]
<<ref>>http://commons.wikimedia.org/wiki/File:FET99.jpg<</ref>>
FETs are majority-charge-carrier devices. The device consists of an active channel through which majority charge carriers, electrons or holes, flow from the source to the drain. Source and drain terminal conductors are connected to semiconductor through ohmic contacts. The conductivity of the channel is a function of potential applied to the gate.
The FET's three terminals are:
* Source (S), through which the majority carriers enter the channel. Conventional current entering the channel at S is designated by IS.
* Drain (D), through which the majority carriers leave the channel. Conventional 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.
ID=IDSS(1-VGS/VP)^2
<ref name=millman>
{{cite book
|author=Millman
|title=Electronic devices and circuits
|year=1985
|pages=384–385
|publisher=McGraw-Hill international book company
|___location=Singapore
|isbn=0-07-Y85505-6}}
</ref>
==Advantages of FET==
The main advantage of the FET is its high input resistance, on the order of 100M ohms or more. Thus, it is a voltage-controlled device, and shows a high degree of isolation between input and output. It is a unipolar device, depending only upon majority current flow. It is less noisy and is thus found in FM tuners for quiet reception. It is relatively immune to radiation. It exhibits no offset voltage at zero drain current and hence makes an excellent signal chopper. It typically has better thermal stability than a BJT.
<ref name=millman>
{{cite book
|author=Millman
|title=Electronic devices and circuits
|year=1985
|pages=384–385
|publisher=McGraw-Hill international book company
|___location=Singapore
|isbn=0-07-Y85505-6}}
</ref>
==Disadvantages of FET==
It has 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.<ref name=Prathamesh>
{{cite book
|author=Allen Mottershead
|title=Electronic devices and circuits
|year= 2004
|publisher=Prentice-Hall of India
|___location=New Delhi
|ISBN-81-203-0124-2}}
</ref>
==MOSFET==
===Depletion type MOSFET===
There are two n-type island on p-type substrate. Between these two n regions there is a n-channel.
The two n-regions form Source and Drain terminals. Gate terminal is to insulated layer of SiO2.
There is conduction without any Gate voltage.
[[File:MOSFET2.jpg|thumb|D MOSFET]]
<<ref>>{http://commons.wikimedia.org/wiki/File:MOSFET2.jpg}<</ref>>
===Enhancement type MOSFET===
Similar to Depletion type , but without n-channel. Hence for conduction there is requirement of some positive Gate voltage which attracts electrons from p-region which conducts from Source to Drain.
[[File:MOSFET4.jpg|thumb|E MOSFET]]
<<ref>>{http://commons.wikimedia.org/wiki/File:MOSFET4.jpg}<</ref>>
<ref name=Prathamesh>
{{cite book
|author=Robert Boylestad
|title=Electronic devices and circuit theory
|year=2004
|publisher=Prentice Hall India
|___location=New Delhi
|ISBN-81-203-2064-6}}
</ref>
==Applications==
* Phase-Shift Oscillator
* Voltage variable resistor (in ohmic region)
* High input resistance solid-state DC voltmeter
<ref name=Prathamesh>
{{cite book
|author=Allen Mottershead
|title=Electronic devices and circuits
|year= 2004
|page=387
|publisher=Prentice-Hall of India
|___location=New Delhi
|ISBN-81-203-0124-2}}
</ref>
=FET amplifier=
==INTRODUCTION==
The main advantage of FET is used for amplification is that it has very high input impedance.
Line 41 ⟶ 131:
==Types of FET amplifiers==
1. Common Gate Amplifier
In this the gate terminal is common to both input and output.
See also : [[Common
2. Common Source Amplifier
In this the source terminal is common to both input and output.
See also : [[Common source]]
3. Common Drain Amplifier
In this the drain terminal is common to both input and output. It is also known as 'Source Follower'.
See Also : [[Common drain]]
<ref>
Line 60 ⟶ 159:
|ISBN-81-203-0124-2}}
</ref>
==References==
{{Reflist}}
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