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27 Ağustos 2010 Cuma
The Triac
anode-cathode voltage it can be switched on (conducting
mode). For a negative anode-cathode voltage, the thyristor
is always off (blocking mode). A device which can be
switched on for both a positive and a negative anodecathode
voltage is the triac.
The triac is simply the anti-parallel connection of two
thyristors.
mode). For a negative anode-cathode voltage, the thyristor
is always off (blocking mode). A device which can be
switched on for both a positive and a negative anodecathode
voltage is the triac.
The triac is simply the anti-parallel connection of two
thyristors.
The Thyristor
The Thyristor
The thyristor is a semiconductor controlled rectifier (SCR)
used in power electronics. It consists of FOUR
semiconductor layers, i.e. there are THREE pn-junctions.
The three terminals are called
Anode (greek: Anodoz = upwards)
Cathode (greek: Kaqodoz = downwards)
Gate (sometimes called “base”)
The figure below depicts the thyristor's layers, whereas the
inner two layers are weakly doped.
The thyristor is a semiconductor controlled rectifier (SCR)
used in power electronics. It consists of FOUR
semiconductor layers, i.e. there are THREE pn-junctions.
The three terminals are called
Anode (greek: Anodoz = upwards)
Cathode (greek: Kaqodoz = downwards)
Gate (sometimes called “base”)
The figure below depicts the thyristor's layers, whereas the
inner two layers are weakly doped.
The Field Effect Transistor
The Field Effect Transistor
With the field effect transistor, the current through a socalled
channel is controlled by means of an electric field.
Hence, field effect transistor. This principle is similar to the
operation of the nowadays rarely used vacuum tube. With
respect to the vacuum tube, the three terminals of the field
effect transistor are called:
Source, which emits the electrons
Drain, which collects the electrons
Gate, which controls the electron flow
The electric field is generated by a voltage. Furthermore,
since only one kind of carrier, e.g. electrons, is involved in
the operation, the field effect transistor is also called
unipolar transistor.
With the field effect transistor, the current through a socalled
channel is controlled by means of an electric field.
Hence, field effect transistor. This principle is similar to the
operation of the nowadays rarely used vacuum tube. With
respect to the vacuum tube, the three terminals of the field
effect transistor are called:
Source, which emits the electrons
Drain, which collects the electrons
Gate, which controls the electron flow
The electric field is generated by a voltage. Furthermore,
since only one kind of carrier, e.g. electrons, is involved in
the operation, the field effect transistor is also called
unipolar transistor.
Why bipolar transistor
Why bipolar transistor?
With the bipolar transistor two kind of carriers are
involved: electrons and holes. Hence, bipolar transistor.
In an n-material, the electrons are the majority carriers.
In a p-material, the holes are the majority carriers.
Since the bipolar transistor consists of two pn-junctions,
there are two possible constellations:
pnp and npn, whereas the npn constellation is most
common.
With the bipolar transistor two kind of carriers are
involved: electrons and holes. Hence, bipolar transistor.
In an n-material, the electrons are the majority carriers.
In a p-material, the holes are the majority carriers.
Since the bipolar transistor consists of two pn-junctions,
there are two possible constellations:
pnp and npn, whereas the npn constellation is most
common.
The Bipolar Transistor, What is a transistor?
The Bipolar Transistor
What is a transistor?
The word transistor is an acronym meaning trans resistor!
That is, a resistor is controlled through a resistance.
Hence a transistor has an input and an output, whereas
in- and output have a common terminal. The transistor
has therefore three terminals!
The three terminals are called
Emitter, which emits electrons
Collector, which collects the electrons
Base, which controls the electron flow
A transistor is made of semiconductors.
What is a transistor?
The word transistor is an acronym meaning trans resistor!
That is, a resistor is controlled through a resistance.
Hence a transistor has an input and an output, whereas
in- and output have a common terminal. The transistor
has therefore three terminals!
The three terminals are called
Emitter, which emits electrons
Collector, which collects the electrons
Base, which controls the electron flow
A transistor is made of semiconductors.
The Solar Cell – some figures of merit
The Solar Cell – some figures of merit
At maximum sunshine, the sun delivers about
1000 W/m2 on the earth's surface.
The efficiency of a solar cell is 10% ... 15%.
Hence, a solar panel of 1 m2 delivers an electrical
peak power of 150 W.
The ouput voltage of a solar cell made of silicon
is about 0.6 V, i.e. several solar cells have to be
connected in series to obtain higher output
voltages.
At maximum sunshine, the sun delivers about
1000 W/m2 on the earth's surface.
The efficiency of a solar cell is 10% ... 15%.
Hence, a solar panel of 1 m2 delivers an electrical
peak power of 150 W.
The ouput voltage of a solar cell made of silicon
is about 0.6 V, i.e. several solar cells have to be
connected in series to obtain higher output
voltages.
The Solar Cell
With the solar cell the effect of electron-hole generation is exploited.
It has been shown that a semiconductor shows better conductivity
at higher temperatures. That is, with increasing energy more bonds
are broken, and the free electrons contribute to electrical current.
Now, with the solar cell, light (commonly sun light) instead of
temperature is the energy source to generate electron-hole pairs.
The solar cell, conceptually a pn-junction, serves as a current
source, i.e. it is an active device!
It has been shown that a semiconductor shows better conductivity
at higher temperatures. That is, with increasing energy more bonds
are broken, and the free electrons contribute to electrical current.
Now, with the solar cell, light (commonly sun light) instead of
temperature is the energy source to generate electron-hole pairs.
The solar cell, conceptually a pn-junction, serves as a current
source, i.e. it is an active device!
Modification of Semiconductors
Modification of Semiconductors
With respect to electronics devices to be designed,
semiconductors must be modified to get a wanted
electrical behaviour:
Selecting the semiconducting material, for
instance: Si, Ge, Se, ...
Forming of compounds, i.e. mixing elements of
the IIIrd group with elements of the Vth group.
Examples: GaAs, InP, ...
Doping of semiconductor, i.e. injecting different
materials (in low quantity) into the
semiconductor in order to increase the number
of free electrons (n-material) or the number of
free holes‡ (p-material).
With respect to electronics devices to be designed,
semiconductors must be modified to get a wanted
electrical behaviour:
Selecting the semiconducting material, for
instance: Si, Ge, Se, ...
Forming of compounds, i.e. mixing elements of
the IIIrd group with elements of the Vth group.
Examples: GaAs, InP, ...
Doping of semiconductor, i.e. injecting different
materials (in low quantity) into the
semiconductor in order to increase the number
of free electrons (n-material) or the number of
free holes‡ (p-material).
Purity
“Pure” means that a material consists to 100% of this
material. In reality there are always “foreign” atoms
(impurities) inside this material. For instance, the purity
level is given as the ratio silicon atoms to one foreign
atom. A typical value is 1028. In words: Among 1028
silicon atoms there is one impurity.
material. In reality there are always “foreign” atoms
(impurities) inside this material. For instance, the purity
level is given as the ratio silicon atoms to one foreign
atom. A typical value is 1028. In words: Among 1028
silicon atoms there is one impurity.
Historical Classification due to conductivity:
Historical Classification due to conductivity:
Nonconductor (Insulator):
Very few free electrons, or no free electrons at all, which
contribute to electrical current. Hence, very low conductivity,
or no conductivity at all.
Dr. Thomas F. BECHTELER Izmir University Electronics and Communication Engineering Dept.
Semiconductor:
A few free electrons which contribute to electrical current.
Hence, conductivity, which is between the conductivity of
conductors and that of insulators.
Conductor:
Huge amount of free electrons which contribute to electrical
current. Hence, conductivity is very high.
Superconductor (see more in “Modern Physics”):
New state of the material below a so-called critical temperature
Tc. Two electrons form a new particle called Cooper-Pair
which does not interact with the atom bodies. Hence, no
losses and therefore zero resistance!
Nonconductor (Insulator):
Very few free electrons, or no free electrons at all, which
contribute to electrical current. Hence, very low conductivity,
or no conductivity at all.
Dr. Thomas F. BECHTELER Izmir University Electronics and Communication Engineering Dept.
Semiconductor:
A few free electrons which contribute to electrical current.
Hence, conductivity, which is between the conductivity of
conductors and that of insulators.
Conductor:
Huge amount of free electrons which contribute to electrical
current. Hence, conductivity is very high.
Superconductor (see more in “Modern Physics”):
New state of the material below a so-called critical temperature
Tc. Two electrons form a new particle called Cooper-Pair
which does not interact with the atom bodies. Hence, no
losses and therefore zero resistance!
What are Semiconductors?
Commonly, when an engineer speaks about
“semiconductors”, he means electrical
elements respectively devices made of a
semiconducting material.
Actually, a semiconductor is just a material.
“semiconductors”, he means electrical
elements respectively devices made of a
semiconducting material.
Actually, a semiconductor is just a material.
System
System
A system is an assembly of interconnected (wired)
circuits packaged in a proper housing to realise a
certain function useful for a customer respectively
user.
computer
television set
mobile phone
RADAR, SONAR
. . .
To describe a system a so-called manual is prepared. It
also informs the user how to use it: What happens
when a certain button is pressed? Its function is often
illustrated by a block diagram.
A system is an assembly of interconnected (wired)
circuits packaged in a proper housing to realise a
certain function useful for a customer respectively
user.
computer
television set
mobile phone
RADAR, SONAR
. . .
To describe a system a so-called manual is prepared. It
also informs the user how to use it: What happens
when a certain button is pressed? Its function is often
illustrated by a block diagram.
Circuit
A circuit is an assembly of interconnected (wired)
elements to realise a certain electrical function.
amplifier
multiplexer
bridge rectifier
To describe an electrical circuit a so-called schematic
is the most convenient mean. By reading the
schematic, the engineer understands the function of
the circuit. To physically implement the circuit, there
are several techniques:
elements to realise a certain electrical function.
amplifier
multiplexer
bridge rectifier
To describe an electrical circuit a so-called schematic
is the most convenient mean. By reading the
schematic, the engineer understands the function of
the circuit. To physically implement the circuit, there
are several techniques:
Datasheets
A datasheet is a paper of documentation in which an
element is described, characterised and, eventually, its
applications are presented.
Most important information is
maximum ratings
DC behaviour
AC behaviour
element is described, characterised and, eventually, its
applications are presented.
Most important information is
maximum ratings
DC behaviour
AC behaviour
Element
An elementary device to create a circuit or a system is
called element. Elements are, for instance,
a wire
resistor
capacitor
inductor
diode
transistor
transforming elements:
microphone, loudspeaker,
Hall element, Peltier element, ...
Elements are considered to be discrete, but no means
lumped, i.e. a transmission line or a single antenna are
considered to be elements.
called element. Elements are, for instance,
a wire
resistor
capacitor
inductor
diode
transistor
transforming elements:
microphone, loudspeaker,
Hall element, Peltier element, ...
Elements are considered to be discrete, but no means
lumped, i.e. a transmission line or a single antenna are
considered to be elements.
Methods for designing electronic circuits:
Methods for designing electronic circuits:
Analytical methods of circuit analysis and
synthesis: Node voltage analysis, mesh current
analysis, ...
Numerical methods: SPICE, Multisim, OrCAD,
Advanced Design System (ADS), QUCS*, …
Physical electronic design: Eagle, Altium, OrCAD,
PCB*, …
Physical mechanic design: AutoCAD, ...
Analytical methods of circuit analysis and
synthesis: Node voltage analysis, mesh current
analysis, ...
Numerical methods: SPICE, Multisim, OrCAD,
Advanced Design System (ADS), QUCS*, …
Physical electronic design: Eagle, Altium, OrCAD,
PCB*, …
Physical mechanic design: AutoCAD, ...
Circuit Design
The process of circuit design can cover systems ranging
from complex electronic systems all the way down to the
individual transistors within an integrated circuit.
Formal circuit design usually involves the following stages:
sometimes, writing the requirement specification after
liaising with the customer
writing a technical proposal to meet the requirements of
the customer specification
synthesising on paper a schematic circuit diagram, an
abstract of electrical or electronic circuits that will meet
the specifications
calculating the component values to meet the operating
specifications under specified conditions
from complex electronic systems all the way down to the
individual transistors within an integrated circuit.
Formal circuit design usually involves the following stages:
sometimes, writing the requirement specification after
liaising with the customer
writing a technical proposal to meet the requirements of
the customer specification
synthesising on paper a schematic circuit diagram, an
abstract of electrical or electronic circuits that will meet
the specifications
calculating the component values to meet the operating
specifications under specified conditions
Subsystems
A subsystem is a part of a larger system. For
instance, a television set may consist of
screen, the visualisation subsystem
audio, the sound subsystem
RF, the receiver subsystem
microcomputer, the control subsystem
Each subsystem is assigned to an engineer/group of
engineers. The interface/boundary of each subsystem
must be well defined to guarantee seamless
interaction and function when assembled.
instance, a television set may consist of
screen, the visualisation subsystem
audio, the sound subsystem
RF, the receiver subsystem
microcomputer, the control subsystem
Each subsystem is assigned to an engineer/group of
engineers. The interface/boundary of each subsystem
must be well defined to guarantee seamless
interaction and function when assembled.
Concept
Systems Engineering is to simply formalise the
approach and in doing so, identify new methods and
research opportunities similar to the way it occurs in
other fields of engineering. Systems Engineering is
interdisciplinary in flavour.
Systems Engineering focuses on defining customer
needs and required functionality early in the
development cycle, documenting requirements, then
proceeding with design synthesis and system
validation while considering the complete problem, the
system life cycle. Systems engineering process can be
decomposed into
a Systems Engineering Technical Process, and
a Systems Engineering Management Process.
approach and in doing so, identify new methods and
research opportunities similar to the way it occurs in
other fields of engineering. Systems Engineering is
interdisciplinary in flavour.
Systems Engineering focuses on defining customer
needs and required functionality early in the
development cycle, documenting requirements, then
proceeding with design synthesis and system
validation while considering the complete problem, the
system life cycle. Systems engineering process can be
decomposed into
a Systems Engineering Technical Process, and
a Systems Engineering Management Process.
Organisation of a Project and its Management
Organisation of a Project and its Management
In order to make a project a success a good planning
for the project itself and the planning of the project
management is essential.
Planning of the project itself: Writing down
inputs, outputs, activities, budget, time
schedule, …
Project management: Assignment of
activities, control, feedback and corrections if
necessary. Software is available!
In order to make a project a success a good planning
for the project itself and the planning of the project
management is essential.
Planning of the project itself: Writing down
inputs, outputs, activities, budget, time
schedule, …
Project management: Assignment of
activities, control, feedback and corrections if
necessary. Software is available!
Project Success and Failure
“Project Success.” – Project is completed on time
and budget, with all features and functions as
specified.
“Project Challenged.” – These were completed, but
were over cost, over time, and/or lacking all of the
features and functions that were originally specified.
“Project Impaired/Failed.” – These projects were
abandoned or cancelled at some point and thus
became total losses.
and budget, with all features and functions as
specified.
“Project Challenged.” – These were completed, but
were over cost, over time, and/or lacking all of the
features and functions that were originally specified.
“Project Impaired/Failed.” – These projects were
abandoned or cancelled at some point and thus
became total losses.
Constraints of a Project
A project must meet the following constraints:
Scope: Tasks which must be accomplished
Time: Time within the tasks must be
accomplished
Budget: Money with which the project must
be managed
Scope: Tasks which must be accomplished
Time: Time within the tasks must be
accomplished
Budget: Money with which the project must
be managed
What is Project Management?
lat. Projektum : “something thrown ahead”
lat. Magnum Agere : “to handle”
PMI (Project Management Institute) – “Project
management is the application of knowledge, skills,
tools and techniques to project activities to meet
project requirements.”
lat. Magnum Agere : “to handle”
PMI (Project Management Institute) – “Project
management is the application of knowledge, skills,
tools and techniques to project activities to meet
project requirements.”
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