PPT: Field Effect Transistors | Analog and Digital Electronics - Electrical Engineering (EE) PDF Download

 Page 1


Field-effect transistors
(FETs)
Page 2


Field-effect transistors
(FETs)
The Field Effect Transistor (FET) The Field Effect Transistor (FET)
l In 1945, Shockley had an idea for making a solid state
device out of semiconductors.
l He reasoned that a strong electrical field could cause the
flow of electricity within a nearby semiconductor.
l He tried to build one, but it didn't work.
l Three years later, Brattain & Bardeen built the first
working transistor, the germanium point-contact
transistor, which was designed as the junction (sandwich)
transistor.
l In 1960 Bell scientist John Atalla developed a new
design based on Shockley's original field-effect theories.
l By the late 1960s, manufacturers converted from
junction type integrated circuits to field effect devices.
Page 3


Field-effect transistors
(FETs)
The Field Effect Transistor (FET) The Field Effect Transistor (FET)
l In 1945, Shockley had an idea for making a solid state
device out of semiconductors.
l He reasoned that a strong electrical field could cause the
flow of electricity within a nearby semiconductor.
l He tried to build one, but it didn't work.
l Three years later, Brattain & Bardeen built the first
working transistor, the germanium point-contact
transistor, which was designed as the junction (sandwich)
transistor.
l In 1960 Bell scientist John Atalla developed a new
design based on Shockley's original field-effect theories.
l By the late 1960s, manufacturers converted from
junction type integrated circuits to field effect devices.
l Field effect devices are those in which current is
controlled by the action of an electron field, rather
than carrier injection.
l Field-effect transistors are so named because a
weak electrical signal coming in through one
electrode creates an electrical field through the rest
of the transistor.
l The FET was known as a “unipolar” transistor.
l The term refers to the fact that current is transported
by carriers of one polarity (majority), whereas in the
conventional bipolar transistor carriers of both
polarities (majority and minority) are involved.
The Field Effect Transistor (FET) The Field Effect Transistor (FET)
Page 4


Field-effect transistors
(FETs)
The Field Effect Transistor (FET) The Field Effect Transistor (FET)
l In 1945, Shockley had an idea for making a solid state
device out of semiconductors.
l He reasoned that a strong electrical field could cause the
flow of electricity within a nearby semiconductor.
l He tried to build one, but it didn't work.
l Three years later, Brattain & Bardeen built the first
working transistor, the germanium point-contact
transistor, which was designed as the junction (sandwich)
transistor.
l In 1960 Bell scientist John Atalla developed a new
design based on Shockley's original field-effect theories.
l By the late 1960s, manufacturers converted from
junction type integrated circuits to field effect devices.
l Field effect devices are those in which current is
controlled by the action of an electron field, rather
than carrier injection.
l Field-effect transistors are so named because a
weak electrical signal coming in through one
electrode creates an electrical field through the rest
of the transistor.
l The FET was known as a “unipolar” transistor.
l The term refers to the fact that current is transported
by carriers of one polarity (majority), whereas in the
conventional bipolar transistor carriers of both
polarities (majority and minority) are involved.
The Field Effect Transistor (FET) The Field Effect Transistor (FET)
The Field Effect Transistor (FET) The Field Effect Transistor (FET)
The family of FET devices may be divided into :
l Junction FET
l Depletion Mode MOSFET
l Enhancement Mode MOSFET
Page 5


Field-effect transistors
(FETs)
The Field Effect Transistor (FET) The Field Effect Transistor (FET)
l In 1945, Shockley had an idea for making a solid state
device out of semiconductors.
l He reasoned that a strong electrical field could cause the
flow of electricity within a nearby semiconductor.
l He tried to build one, but it didn't work.
l Three years later, Brattain & Bardeen built the first
working transistor, the germanium point-contact
transistor, which was designed as the junction (sandwich)
transistor.
l In 1960 Bell scientist John Atalla developed a new
design based on Shockley's original field-effect theories.
l By the late 1960s, manufacturers converted from
junction type integrated circuits to field effect devices.
l Field effect devices are those in which current is
controlled by the action of an electron field, rather
than carrier injection.
l Field-effect transistors are so named because a
weak electrical signal coming in through one
electrode creates an electrical field through the rest
of the transistor.
l The FET was known as a “unipolar” transistor.
l The term refers to the fact that current is transported
by carriers of one polarity (majority), whereas in the
conventional bipolar transistor carriers of both
polarities (majority and minority) are involved.
The Field Effect Transistor (FET) The Field Effect Transistor (FET)
The Field Effect Transistor (FET) The Field Effect Transistor (FET)
The family of FET devices may be divided into :
l Junction FET
l Depletion Mode MOSFET
l Enhancement Mode MOSFET
Junction FETs (JFETs) Junction FETs (JFETs)
l JFETs consists of a piece of high-resistivity
semiconductor material (usually Si) which
constitutes a channel for the majority carrier
flow.
l Conducting semiconductor channel between two
ohmic contacts – source & drain