هندسة الأزهر
السلام عليكم ..اهلا وسهلا بك عزيزى الزائر نورت المنتدى بزيارتك لنا ..انت غير مسجل فى منتدى كليه هندسه الازهر ..سوف تتمتع بالعديد من المميزات اذا قمت بالتسجيل وذلك بالضغط على الزر اسفله(زر التسجيل) اما اذا كنت مسجل بالفعل ..فلتسجل دخولك عن طريق الضغط على الزر اسفله(زر الدخول) اما اذا كنت تريد اخفاء هذه الرساله فاضغط على الزر اسفله (زر الاخفاء)

هندسة الأزهر

معا لنتواصل.... من أجل حياة جامعية أفضل.
 
الرئيسيةدخولالتسجيلمكتبة الصوردخول الاعضاء

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 الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......

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thebest-engineer
مشرف قسم الهندسة الكهربية
مشرف قسم الهندسة الكهربية


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العمل/الترفيه : طالب(ولا حول ولاقوة الا بالله)
الـكـلـيـــة : : جعلتني مهندسا

مُساهمةموضوع: الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......   الثلاثاء سبتمبر 15, 2009 7:41 am


السلام عليكم يابشمهندسين ويابشمهندسات
الموضوع دوة للشباب اللي طلعو من اعدادي بسلام
وقررو يدخلو قسم الهندسة الكهربية
اي حاجه تحب تعرفها عن القسم والدكاترة والمواد..........
انا تحت امرك
بس اتفضل أسأل؟؟؟؟؟؟
الرجوع الى أعلى الصفحة اذهب الى الأسفل
smsm
مهندس فعال
مهندس فعال


عدد الرسائل : 491
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العمل/الترفيه : مهندسة ان شاء الله
الـكـلـيـــة : : هندسة

مُساهمةموضوع: رد: الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......   الثلاثاء سبتمبر 15, 2009 5:53 pm

الف شكر يا بشمهندس علي روح التعاون الجميله دي
وان شاء الله تقدر تفيدنا
الرجوع الى أعلى الصفحة اذهب الى الأسفل
شيماء الحو
مهندس جديد
مهندس جديد


عدد الرسائل : 1
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العمل/الترفيه : الاستفادةوالافادة
الـكـلـيـــة : : الهندسة

مُساهمةموضوع: رد: الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......   الأحد أبريل 04, 2010 4:47 am

من فضلك ياباشمهندس ممكن حضرتك تفيدنى فى مادة الالكترونيات لان الدكتور طالب مننا معلومات عن الباب الرابع
وهو بعنوان SPECIAL PURPOUS OF DIODE
الرجوع الى أعلى الصفحة اذهب الى الأسفل
thebest-engineer
مشرف قسم الهندسة الكهربية
مشرف قسم الهندسة الكهربية


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الـكـلـيـــة : : جعلتني مهندسا

مُساهمةموضوع: رد: الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......   الإثنين أبريل 05, 2010 3:49 am

ازيك يابشمهندسة شيماء
ياريت تحددي بالظبط ايه المطلوب عن الباب
يعني الدكتور طالب تقرير عن الموضوع ولا ايه بالظبط
ولا معلومات عن العملي

_________________

الكلام الحلو ما يطلع الا ليها
مصر بلد الامان والرب حاميها
وحارس شبابها وكل مبانيها
مصر بلدنا هتفضل قويه
بيكم يا شبابها هتفضل عفيه
مايفرح فيها عدو ولا بيها
ويموت ونفسو يدوس اراضيها
ويمشى على ترابها يتمنى يرضيها
مصر عمرها اطول من كل ظالم
واللى راح قبلها كان قدامها بيتظاهر
انو عليها قدر وكان كله مظاهر


الرجوع الى أعلى الصفحة اذهب الى الأسفل
thebest-engineer
مشرف قسم الهندسة الكهربية
مشرف قسم الهندسة الكهربية


عدد الرسائل : 916
العمر : 27
العمل/الترفيه : طالب(ولا حول ولاقوة الا بالله)
الـكـلـيـــة : : جعلتني مهندسا

مُساهمةموضوع: رد: الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......   الإثنين أبريل 05, 2010 3:55 am

عموما يابشمهندسة دي معلومات عن الموضوع بالانجليش وفيها زيادة عن الكتاب
دا لو هو عاوز انجليش
Schottky diodes








Schottky diodes are constructed of a
metal-to-N junction rather than a P-N semiconductor junction.
Also known as hot-carrier diodes, Schottky diodes are
characterized by fast switching times (low reverse-recovery time), low
forward voltage drop (typically 0.25 to 0.4 volts for a metal-silicon
junction), and low junction capacitance.


The schematic symbol for a schottky diode
is shown in Figure
below.





Schottky diode schematic symbol.



The forward voltage drop (VF), reverse-recovery time (trr),
and junction capacitance (CJ) of
Schottky diodes are closer to ideal than the average “rectifying” diode. This makes them well suited for
high-frequency applications. Unfortunately, though, Schottky diodes
typically have lower forward current (IF) and reverse voltage
(VRRM and VDC) ratings than rectifying diodes and
are thus unsuitable for applications involving substantial amounts of power. Though they are used in low voltage
switching regulator power supplies.


Schottky diode technology finds broad
application in high-speed computer circuits, where the fast switching
time equates to high speed capability, and the low forward voltage drop
equates to less power dissipation when conducting.


Switching regulator power supplies operating at 100's of kHz cannot use conventional silicon diodes as
rectifiers because of their slow switching
speed . When the signal applied to a diode
changes from forward to reverse bias, conduction continues for a short
time, while carriers are being swept out of
the depletion region. Conduction only ceases after this tr
reverse recovery time
has expired. Schottky diodes have a shorter
reverse recovery time.


Regardless of switching speed, the 0.7 V
forward voltage drop of silicon diodes
causes poor efficiency in low voltage supplies. This is not a problem
in, say, a 10 V supply. In a 1 V supply the 0.7 V drop is a substantial
portion of the output. One solution is to
use a schottky power diode which has a
lower forward drop.










Tunnel diodes






Tunnel diodes exploit a strange quantum phenomenon called resonant
tunneling
to provide a negative resistance forward-bias
characteristics. When a small forward-bias voltage is applied across a
tunnel diode, it begins to conduct current.
(Figure
below(b)) As the voltage is increased, the current increases and
reaches a peak value called the peak current (IP). If
the voltage is increased a little more, the current actually begins to decrease
until it reaches a low point called the valley current (IV).
If the voltage is increased further yet, the current begins to
increase again, this time without decreasing into another “valley.”

The schematic symbol for the tunnel diode
shown in Figure
below(a).





Tunnel diode (a) Schematic symbol.
(b) Current vs voltage plot (c) Oscillator.






The forward voltages necessary to drive a tunnel diode
to its peak and valley currents are known as peak voltage (VP)
and valley voltage (VV), respectively. The region on the
graph where current is decreasing while applied voltage is increasing
(between VP and VV on the horizontal scale) is
known as the region of negative
resistance
.





Tunnel diodes, also known as Esaki diodes in honor of their Japanese inventor Leo Esaki, are able to
transition between peak and valley current levels very quickly,
“switching” between high and low states of
conduction much faster than even Schottky diodes. Tunnel diode characteristics are also relatively
unaffected by changes in temperature.





Reverse breakdown voltage versus doping level. After Sze [SGG]



Tunnel diodes are heavily doped in both the P and N regions, 1000 times
the level in a rectifier. This can be seen in Figure
above. Standard diodes are to the far left, zener diodes near to the
left, and tunnel diodes to the right of
the dashed line. The heavy doping produces an unusually thin depletion
region. This produces an unusually low reverse breakdown voltage with
high leakage. The thin depletion region causes high capacitance. To
overcome this, the tunnel diode junction
area must be tiny. The forward diode
characteristic consists of two regions: a
normal forward diode characteristic with
current rising exponentially beyond VF, 0.3 V for Ge, 0.7 V
for Si. Between 0 V and VF is an additional “negative
resistance” characteristic peak. This is due to quantum mechanical
tunneling involving the dual particle-wave nature of
electrons. The depletion region is thin enough compared with the
equivalent wavelength of the electron that
they can tunnel through. They do not have to overcome the normal forward
diode voltage VF. The energy
level of the conduction band of the N-type material overlaps the level of the valence band in the P-type region. With
increasing voltage, tunneling begins; the levels overlap; current
increases, up to a point. As current increases further, the energy
levels overlap less; current decreases with increasing voltage. This is
the “negative resistance” portion of the
curve.


Tunnel diodes are not good rectifiers, as they have relatively high
“leakage” current when reverse-biased. Consequently, they find
application only in special circuits where
their unique tunnel effect has value. To exploit the tunnel effect,
these diodes are maintained at a bias voltage somewhere between the peak
and valley voltage levels, always in a forward-biased polarity (anode
positive, and cathode negative).


Perhaps the most common application of a
tunnel diode is in simple high-frequency
oscillator circuits as in Figure
above(c), where it allows a DC voltage source to contribute power to
an LC “tank” circuit, the diode conducting
when the voltage across it reaches the peak (tunnel) level and
effectively insulating at all other voltages. The resistors bias the
tunnel diode at a few tenths of a volt centered on the negative resistance
portion of the characteristic curve. The
L-C resonant circuit may be a section of
waveguide for microwave operation. Oscillation to 5 GHz is possible.


At one time the tunnel diode was the only
solid-state microwave amplifier available. Tunnel diodes were popular
starting in the 1960's. They were longer lived than traveling wave tube
amplifiers, an important consideration in satellite transmitters.
Tunnel diodes are also resistant to radiation because of the heavy doping. Today various transistors
operate at microwave frequencies. Even small signal tunnel diodes are
expensive and difficult to find today. There is one remaining
manufacturer of germanium tunnel diodes,
and none for silicon devices. They are sometimes used in military
equipment because they are insensitive to radiation and large
temperature changes.

There has been some research involving possible integration of silicon tunnel diodes into CMOS integrated
circuits. They are thought to be capable of
switching at 100 GHz in digital circuits. The sole manufacturer of germanium devices produces them one at a
time. A batch process for silicon tunnel diodes must be developed, then
integrated with conventional CMOS processes. [SZL]


The Esaki tunnel diode should not be
confused with the resonant tunneling diode
CH
2, of more complex construction from
compound semiconductors. The RTD is a more recent development capable of higher speed.










Light-emitting diodes



Diodes, like all semiconductor devices, are governed by the principles
described in quantum physics. One of these
principles is the emission of
specific-frequency radiant energy whenever electrons fall from a higher
energy level to a lower energy level. This is the same principle at
work in a neon lamp, the characteristic pink-orange glow of ionized neon due to the specific energy
transitions of its electrons in the midst of an electric current. The unique color of a neon lamp's glow is due to the fact that its
neon gas inside the tube, and not due to the particular amount of current through the tube or voltage between
the two electrodes. Neon gas glows pinkish-orange over a wide range of ionizing voltages and currents. Each
chemical element has its own “signature” emission of
radiant energy when its electrons “jump” between different, quantized
energy levels. Hydrogen gas, for example, glows red when ionized;
mercury vapor glows blue. This is what makes spectrographic
identification of elements possible.






Electrons flowing through a PN junction experience similar transitions
in energy level, and emit radiant energy as they do so. The frequency of this radiant energy is determined by the
crystal structure of the semiconductor
material, and the elements comprising it. Some semiconductor junctions,
composed of special
chemical combinations, emit radiant energy within the spectrum of visible light as the electrons change energy
levels. Simply put, these junctions glow when forward biased. A
diode intentionally designed to glow like a
lamp is called a light-emitting diode,
or LED.


Forward biased silicon diodes give off heat as electron and holes from
the N-type and P-type regions, respectively, recombine at the junction.
In a forward biased LED, the recombination of
electrons and holes in the active region in Figure
below (c) yields photons. This process is known as electroluminescence.
To give off photons, the potential barrier through which the electrons
fall must be higher than for a silicon diode.
The forward diode drop can range to a few
volts for some color LEDs.




Diodes made from a combination of the
elements gallium, arsenic, and phosphorus (called gallium-arsenide-phosphide)
glow bright red, and are some of the most
common LEDs manufactured. By altering the chemical constituency of the PN junction, different colors may be
obtained. Early generations of LEDs were
red, green, yellow, orange, and infra-red, later generations included
blue and ultraviolet, with violet being the latest color added to the
selection. Other colors may be obtained by combining two or more
primary-color (red, green, and blue) LEDs together in the same package,
sharing the same optical lens. This allowed for multicolor LEDs, such
as tricolor LEDs (commercially available in the 1980's) using red and
green (which can create yellow) and later RGB LEDs (red, green, and
blue), which cover the entire color spectrum.




The schematic symbol for an LED is a regular diode
shape inside of a circle, with two small
arrows pointing away (indicating emitted light), shown in Figure
below.





LED, Light Emitting Diode: (a)
schematic symbol. (b) Flat side and short lead of
device correspond to cathode. (c) Cross section of
Led die.



This notation of having two small arrows
pointing away from the device is common to the schematic symbols of all light-emitting semiconductor devices.
Conversely, if a device is light-activated (meaning that incoming
light stimulates it), then the symbol will have two small arrows
pointing toward it. LEDs can sense light. They generate a
small voltage when exposed to light, much like a solar cell on a small
scale. This property can be gainfully applied in a variety of light-sensing circuits.



Because LEDs are made of different chemical
substances than silicon diodes, their forward voltage drops will be
different. Typically, LEDs have much larger forward voltage drops than
rectifying diodes, anywhere from about 1.6 volts to over 3 volts,
depending on the color. Typical operating current for a standard-sized
LED is around 20 mA. When operating an LED from a DC voltage source
greater than the LED's forward voltage, a series-connected “dropping”
resistor must be included to prevent full source voltage from damaging
the LED. Consider the example circuit in Figure
below (a) using a 6 V source.





Setting LED current at 20 ma. (a) for a 6 V source, (b) for a 24 V
source.



With the LED dropping 1.6 volts, there will be 4.4 volts dropped across
the resistor. Sizing the resistor for an LED current of 20 mA is as simple as taking its voltage drop
(4.4 volts) and dividing by circuit current (20 mA), in accordance with
Ohm's Law (R=E/I). This gives us a figure of
220 Ω. Calculating power dissipation for this resistor, we take its
voltage drop and multiply by its current (P=IE), and end up with 88 mW,
well within the rating of a 1/8 watt
resistor. Higher battery voltages will require larger-value dropping
resistors, and possibly higher-power rating resistors as well. Consider
the example in Figure
above (b) for a supply voltage of 24
volts:



Here, the dropping resistor must be increased to a size of 1.12 kΩ to drop 22.4 volts at 20 mA so that
the LED still receives only 1.6 volts. This also makes for a higher
resistor power dissipation: 448 mW, nearly one-half a watt of power! Obviously, a resistor rated for 1/8
watt power dissipation or even 1/4 watt dissipation will overheat if
used here.


Dropping resistor values need not be precise for LED circuits. Suppose
we were to use a 1 kΩ resistor instead of a
1.12 kΩ resistor in the circuit shown above. The result would be a
slightly greater circuit current and LED voltage drop, resulting in a
brighter light from the LED and slightly reduced service life. A
dropping resistor with too much resistance (say, 1.5 kΩ instead of 1.12 kΩ) will result in less circuit current,
less LED voltage, and a dimmer light. LEDs are quite tolerant of variation in applied power, so you need not
strive for perfection in sizing the dropping resistor.


Multiple LEDs are sometimes required, say in lighting. If LEDs are
operated in parallel, each must have its own current limiting resistor
as in Figure
below (a) to ensure currents dividing more equally.

However, it is more efficient to operate LEDs in series (Figure
below (b)) with a single dropping resistor. As the number of series LEDs increases the series resistor
value must decrease to maintain current, to a point. The number of LEDs in series (Vf) cannot exceed
the capability of the power supply.

Multiple series strings may be employed as in Figure
below (c).


In spite of equalizing the currents in
multiple LEDs, the brightness of the
devices may not match due to variations in the individual parts. Parts
can be selected for brightness matching for critical applications.





Multiple LEDs: (a) In parallel, (b) in series, (c) series-parallel



Also because of their unique chemical
makeup, LEDs have much, much lower peak-inverse voltage (PIV) ratings
than ordinary rectifying diodes. A typical LED might only be rated at 5
volts in reverse-bias mode. Therefore, when using alternating current
to power an LED, connect a protective rectifying diode
anti-parallel with the LED to prevent reverse breakdown every other
half-cycle as in Figure
below (a).





Safely driving an LED with AC: (a) from 24 VAC, (b) from 240 VAC.



If the LED is driven from a 240 VAC source, the Figure
above (a) voltage source is increased from 24 VAC to 240 VAC, the
resistor from 1.12 kΩ to 12 kΩ. The power dissipated in the 12 kΩ
resistor is an unattractive 4.8 watts.




P = VI = (240 V)(20 mA) = 4.8 watt




A potential solution is to replace the 12 kΩ resistor with a
non-dissipative 12 kΩ capacitive reactance. This would be Figure
above (b) with the resistor shorted. That circuit at (b), missing
the resistor, was published in an electrical engineering journal. This
author constructed the circuit. It worked the first time it was powered
“on,” but not thereafter upon “power on”. Each time it was powered “on,”
it got dimmer until it failed completely. Why? If “power on” occurs
near a zero crossing of the AC sinewave,
the circuit works. However, if powered “on” at, say, the peak of the sinewave, the voltage rises abruptly from
zero to the peak. Since the current through the capacitor is i =
C(dv/dt), the current spikes to a very large value exceeding the “surge
current” rating of the LED, destroying it.


The solution is to design a capacitor for the continuous current of the LED, and a series resistor to limit
current during “power on” to the surge current rating of the LED. Often the surge current rating of an LED is ten times higher than the
continuous current rating. (Though, this is not true of high current illumination grade LED's.) We
calculate a capacitor to supply 20 mA continuous current, then select a
resistor having resistance of 1/10 th the
capacitive reactance.



I = 20 mA
Xc = (240 V) / (20 mA) = 12 kΩ
Xc = 1/2πfc
C = 1/2πXc = 1/2π60(12 kΩ = 0.22 µF
R = (0.10)Xc= (0.10)(12kΩ) = 1.2 kΩ
P = I2R = (20 mA)2(1.2 kΩ) = 0.48 watt


The resistor limits the LED current to 200 mA during the “power on”
surge. Thereafter it passes 20 mA as limited by the capacitor. The 1.2 kresistor
dissipates 0.48 watts compared with 4.8 watts for the 12 kΩ resistor
circuit.


What component values would be required to operate the circuit on 120
VAC? One solution is to use the 240 VAC circuit on 120 VAC with no
change in component values, halving the LED continuous current to 10 mA.
If operation at 20 mA is required, double the capacitor value and halve
the resistor value.


The anti-parallel diodes in Figure
above can be replaced with an anti-parallel LED. The resulting pair of anti-parallel LED's illuminate on alternating
half-cycles of the AC sinewave. This
configuration draws 20 ma, splitting it equally between the LED's on
alternating AC half cycles. Each LED only receives 10 mA due to this
sharing. The same is true of the LED
anti-parallel combination with a rectifier. The LED only receives 10 ma.
If 20 mA was required for the LED(s), The capacitor value in µF could
be doubled and the resistor halved.



The forward voltage drop of LED's is
inversely proportional to the wavelength (λ). As wavelength decreases
going from infrared to visible colors to ultraviolet, Vf
increases. While this trend is most obvious in the various devices from a
single manufacturer, The voltage range for a particular color LED from
various manufacturers varies. This range of
voltages is shown in Table
below.



Optical and electrical properties of LED's

LEDλ nm (= 10 -9m)Vf(from)Vf (to)
infrared9401.21.7
red6601.52.4
orange602-6202.12.2
yellow, green560-5951.72.8
white, blue, violet-34
ultraviolet3704.24.8


As lamps, LEDs are superior to incandescent bulbs in many ways. First
and foremost is efficiency: LEDs output far more light power per watt of electrical input than an incandescent lamp.
This is a significant advantage if the circuit in question is
battery-powered, efficiency translating to longer battery life. Second
is the fact that LEDs are far more reliable, having a much greater
service life than incandescent lamps. This is because LEDs are “cold”
devices: they operate at much cooler temperatures than an incandescent
lamp with a white-hot metal filament, susceptible to breakage from
mechanical and thermal shock. Third is the high speed at which LEDs may
be turned on and off. This advantage is also due to the “cold”
operation of LEDs: they don't have to
overcome thermal inertia in transitioning from off to on or vice versa.
For this reason, LEDs are used to transmit digital (on/off) information
as pulses of light, conducted in empty
space or through fiber-optic cable, at very high rates of speed (millions of
pulses per second).



LEDs excel in monochromatic lighting applications like traffic signals
and automotive tail lights. Incandescents are abysmal in this
application since they require filtering, decreasing efficiency. LEDs do
not require filtering.


One major disadvantage of using LEDs as
sources of illumination is their
monochromatic (single-color) emission. No one wants to read a book
under the light of a red, green, or blue
LED. However, if used in combination, LED colors may be mixed for a
more broad-spectrum glow. A new broad spectrum light source is the
white LED. While small white panel indicators have been available for
many years, illumination grade devices are still in development.





Efficiency of
lighting


Lamp typeEfficiency lumen/wattLife hrsnotes
White LED35100,000costly
White LED, future100100,000R&D target
Incandescent121000inexpensive
Halogen15-172000high quality light
Compact fluorescent50-10010,000cost
effective
Sodium vapor, lp70-20020,000outdoor
Mercury vapor13-4818,000outdoor


A white LED is a blue LED exciting a phosphor which emits yellow light.
The blue plus yellow approximates white light. The nature of the phosphor determines the characteristics of the light. A red phosphor may be added to
improve the quality of the yellow plus blue
mixture at the expense of efficiency.
Table
above compares white illumination LEDs to expected future devices
and other conventional lamps. Efficiency is measured in lumens of light output per watt of
input power. If the 50 lumens/watt device can be improved to 100
lumens/watt, white LEDs will be comparable to compact fluorescent lamps
in efficiency.



LEDs in general have been a major subject of
R&D since the 1960's. Because of this
it is impractical to cover all geometries, chemistries, and
characteristics that have been created over the decades. The early
devices were relatively dim and took moderate currents. The efficiencies
have been improved in later generations to the point it is hazardous to
look closely and directly into an illuminated LED. This can result in
eye damage, and the LEDs only required a minor increase in dropping
voltage (Vf) and current. Modern high intensity devices have reached 180
lumens using 0.7 Amps (82 lumens/watt, Luxeon Rebel series cool white),
and even higher intensity models can use even higher currents with a
corresponding increase in brightness. Other developments, such as
quantum dots, are the subject of current
research, so expect to see new things for these devices in the future







Laser diodes






The laser diode is a further
development upon the regular light-emitting diode,
or LED. The term “laser” itself is actually an acronym, despite the
fact its often written in lower-case letters. “Laser” stands for Light
Amplification by Stimulated Emission of Radiation, and refers to another
strange quantum process whereby characteristic light emitted by
electrons falling from high-level to low-level energy states in a
material stimulate other electrons in a substance to make similar
“jumps,” the result being a synchronized output of
light from the material. This synchronization extends to the actual phase
of the emitted light, so that all light
waves emitted from a “lasing” material are not just the same frequency
(color), but also the same phase as each other, so that they reinforce
one another and are able to travel in a very tightly-confined,
nondispersing beam. This is why laser light stays so remarkably focused
over long distances: each and every light wave coming from the laser is
in step with each other.





(a) White light of many wavelengths.
(b) Mono-chromatic LED light, a single wavelength. (c) Phase coherent
laser light.







Incandescent lamps produce “white” (mixed-frequency, or mixed-color)
light as in Figure
above (a).

Regular LEDs produce monochromatic light: same frequency (color), but
different phases, resulting in similar beam dispersion in Figure
above (b).

Laser LEDs produce coherent light: light that is both
monochromatic (single-color) and monophasic (single-phase), resulting in
precise beam confinement as in Figure
above (c).


Laser light finds wide application in the modern world: everything from
surveying, where a straight and nondispersing light beam is very useful
for precise sighting of measurement
markers, to the reading and writing of
optical disks, where only the narrowness of
a focused laser beam is able to resolve the microscopic “pits” in the
disk's surface comprising the binary 1's and 0's of
digital information.


Some laser diodes require special
high-power “pulsing” circuits to deliver large quantities of voltage and current in short bursts. Other
laser diodes may be operated continuously at lower power. In the
continuous laser, laser action occurs only within a certain range of diode current,
necessitating some form of
current-regulator circuit. As laser diodes age, their power
requirements may change (more current required for less output power),
but it should be remembered that low-power laser diodes, like LEDs, are
fairly long-lived devices, with typical service lives in the tens of thousands of
hours.










Photodiodes






A photodiode is a diode optimized to
produce an electron current flow in response to irradiation by
ultraviolet, visible, or infrared light. Silicon is most often used to
fabricate photodiodes; though, germanium and gallium arsenide can be
used. The junction through which light enters the semiconductor must be
thin enough to pass most of the light on
to the active region (depletion region) where light is converted to
electron hole pairs.



In Figure
below a shallow P-type diffusion into an N-type wafer produces a PN
junction near the surface of the wafer. The
P-type layer needs to be thin to pass as much light as possible. A
heavy N+ diffusion on the back of the wafer
makes contact with metalization. The top metalization may be a fine
grid of metallic fingers on the top of the wafer for large cells. In small
photodiodes, the top contact might be a sole bond wire contacting the
bare P-type silicon top.






Photodiode: Schematic symbol and cross section.


Light entering the top of the photodiode
stack fall off exponentially in with depth of
the silicon. A thin top P-type layer allows most photons to pass into
the depletion region where electron-hole pairs are formed. The electric
field across the depletion region due to the built in diode potential causes electrons to be swept into
the N-layer, holes into the P-layer. Actually electron-hole pairs may
be formed in any of the semiconductor
regions. However, those formed in the depletion region are most likely
to be separated into the respective N and P-regions. Many of the electron-hole pairs formed in the P and
N-regions recombine. Only a few do so in the depletion region. Thus, a
few electron-hole pairs in the N and P-regions, and most in the
depletion region contribute to photocurrent, that current
resulting from light falling on the photodiode.


The voltage out of a photodiode may be
observed. Operation in this photovoltaic (PV) mode is not linear
over a large dynamic range, though it is sensitive and has low noise at
frequencies less than 100 kHz. The preferred mode of operation is often photocurrent (PC)
mode because the current is linearly proportional to light flux over
several decades of intensity, and higher
frequency response can be achieved. PC mode is achieved with reverse
bias or zero bias on the photodiode. A current amplifier (transimpedance
amplifier) should be used with a photodiode in PC mode. Linearity and
PC mode are achieved as long as the diode
does not become forward biased.


High speed operation is often required of
photodiodes, as opposed to solar cells. Speed is a function of diode
capacitance, which can be minimized by decreasing cell area. Thus, a
sensor for a high speed fiber optic link will use an area no larger than
necessary, say 1 mm2. Capacitance may also be decreased by
increasing the thickness of the depletion
region, in the manufacturing process or by increasing the reverse bias
on the diode.








PIN diode The p-i-n diode or PIN diode
is a photodiode with an intrinsic layer between the P and N-regions as
in Figure
below. The P-Intrinsic-N structure increases
the distance between the P and N conductive layers, decreasing
capacitance, increasing speed. The volume of
the photo sensitive region also increases, enhancing conversion
efficiency. The bandwidth can extend to 10's of
gHz. PIN photodiodes are the preferred for high sensitivity, and high
speed at moderate cost.






PIN photodiode: The intrinsic region increases the thickness of the depletion region.






Avalanche photo diode:An avalanche
photodiode (APD)
designed to operate at high reverse bias exhibits
an electron multiplier effect analogous to a photomultiplier tube. The
reverse bias can run from 10's of volts to
nearly 2000 V. The high level of reverse
bias accelerates photon created electron-hole pairs in the intrinsic
region to a high enough velocity to free additional carriers from
collisions with the crystal lattice. Thus, many electrons per photon
result. The motivation for the APD is to achieve amplification within
the photodiode to overcome noise in external amplifiers. This works to
some extent. However, the APD creates noise of
its own. At high speed the APD is superior to a PIN diode amplifier combination, though not for low
speed applications. APD's are expensive, roughly the price of a photomultiplier tube. So, they are only
competitive with PIN photodiodes for niche applications. One such
application is single photon counting as applied to nuclear physics.






Solar cells




A photodiode optimized for efficiently delivering power to a load is the
solar cell. It operates in photovoltaic mode (PV) because it is
forward biased by the voltage developed across the load resistance.


Monocrystalline solar cells are manufactured in a process similar to
semiconductor processing. This involves growing a single crystal boule
from molten high purity silicon (P-type), though, not as high purity as
for semiconductors. The boule is diamond sawed or wire sawed into
wafers. The ends of the boule must be
discarded or recycled, and silicon is lost in the saw kerf. Since modern
cells are nearly square, silicon is lost in squaring the boule. Cells
may be etched to texture (roughen) the surface to help trap light
within the cell. Considerable silicon is lost in producing the 10 or 15
cm square wafers. These days (2007) it is common for solar cell
manufacturer to purchase the wafers at this stage from a supplier to
the semiconductor industry.


P-type Wafers are loaded back-to-back into fused silica boats exposing
only the outer surface to the N-type dopant in the diffusion furnace.
The diffusion process forms a thin n-type layer on the top of the cell. The diffusion also shorts the edges of the cell front to back. The periphery must be
removed by plasma etching to unshort the cell. Silver and or aluminum
paste is screened on the back of the cell,
and a silver grid on the front. These are sintered in a furnace for
good electrical contact. (Figure
below)


The cells are wired in series with metal ribbons. For charging 12 V
batteries, 36 cells at approximately 0.5 V are vacuum laminated between
glass, and a polymer metal back. The glass may have a textured surface
to help trap light.






Silicon Solar cell


The ultimate commercial high efficiency (21.5%) single crystal silicon
solar cells have all contacts on the back of
the cell. The active area of the cell is
increased by moving the top (-) contact conductors to the back of the cell. The top (-) contacts are normally
made to the N-type silicon on top of the
cell. In Figure
below the (-) contacts are made to N+ diffusions on the
bottom interleaved with (+) contacts. The top surface is textured to aid
in trapping light within the cell.. [VSW]






High efficiency solar cell with all contacts on the back. Adapted
from Figure 1 [VSW]






Multicyrstalline silicon cells start out as molten silicon cast
into a rectangular mold. As the silicon cools, it crystallizes into a
few large (mm to cm sized) randomly oriented crystals instead of a single one. The remainder of the process is the same as for single crystal
cells. The finished cells show lines dividing the individual crystals,
as if the cells were cracked. The high efficiency is not quite as high
as single crystal cells due to losses at crystal grain boundaries. The
cell surface cannot be roughened by etching due to the random
orientation of the crystals. However, an
antireflectrive coating improves efficiency. These cells are competitive
for all but space applications.



Three layer cell: The highest efficiency solar cell is a stack of three cells tuned to absorb different
portions of the solar spectrum. Though
three cells can be stacked atop one another, a monolithic single crystal
structure of 20 semiconductor layers is
more compact. At 32 % efficiency, it is now (2007) favored over silicon
for space application. The high cost prevents it from finding many earth
bound applications other than concentrators based on lenses or mirrors.



Intensive research has recently produced a version enhanced for
terrestrial concentrators at 400 - 1000 suns and 40.7% efficiency. This
requires either a big inexpensive Fresnel lens or reflector and a small
area of the expensive semiconductor. This
combination is thought to be competitive with inexpensive silicon cells
for solar power plants. [RRK]


[LZy]



Metal organic chemical vapor deposition (MOCVD) deposits the
layers atop a P-type germanium substrate. The top layers of N and P-type gallium indium phosphide (GaInP)
having a band gap of 1.85 eV, absorbs
ultraviolet and visible light. These wavelengths have enough energy to
exceed the band gap. Longer wavelengths (lower energy) do not have
enough energy to create electron-hole pairs, and pass on through to the
next layer. A gallium arsenide layers having a band gap of 1.42 eV, absorbs near infrared light. Finally
the germanium layer and substrate absorb far infrared. The series of three cells produce a voltage which is the sum
of the voltages of
the three cells. The voltage developed by each material is 0.4 V less
than the band gap energy listed in Table
below. For example, for GaInP: 1.8 eV/e - 0.4 V = 1.4 V. For all
three the voltage is 1.4 V + 1.0 V + 0.3 V = 2.7 V. [BRB]








High efficiency triple layer solar cell.

LayerBand gapLight absorbed
Gallium indium phosphide1.8 eVUV, visible
Gallium arsenide1.4 eVnear infrared
Germanium0.7 eVfar infrared






Crystalline solar cell arrays have a long useable life. Many arrays are
guaranteed for 25 years, and believed to be good for 40 years. They do
not suffer initial degradation compared with amorphous silicon.


Both single and multicrystalline solar cells are based on silicon
wafers. The silicon is both the substrate and the active device layers.
Much silicon is consumed. This kind of
cell has been around for decades, and takes approximately 86% of the solar electric market. For further
information about crystalline solar cells see Honsberg. [CHS]


Amorphous silicon thin film solar cells use tiny amounts of the active raw material, silicon.
Approximately half the cost of conventional
crystalline solar cells is the solar cell grade silicon. The thin film
deposition process reduces this cost. The downside is that efficiency is
about half that of conventional
crystalline cells. Moreover, efficiency degrades by 15-35% upon exposure
to sunlight. A 7% efficient cell soon ages to 5% efficiency. Thin film
amorphous silicon cells work better than crystalline cells in dim light.
They are put to good use in solar powered calculators.




Non-silicon based solar cells make up about 7% of
the market. These are thin-film polycrystalline products. Various
compound semiconductors are the subject of
research and development. Some non-silicon products are in production.
Generally, the efficiency is better than amorphous silicon, but not
nearly as good as crystalline silicon.


Cadmium telluride as a polycrystalline thin film on metal or
glass can have a higher efficiency than amorphous silicon thin films. If
deposited on metal, that layer is the negative contact to the cadmium
telluride thin film. The transparent P-type cadmium sulfide atop the
cadmium telluride serves as a buffer layer. The positive top contact is
transparent, electrically conductive fluorine doped tin oxide. These
layers may be laid down on a sacrificial foil in place of the glass in the process in the following
pargraph. The sacrificial foil is removed after the cell is mounted to a
permanent substrate.





Cadmium telluride solar cell on glass or metal.


A process for depositing cadmium telluride on glass begins with the
deposition of N-type transparent,
electrically conducive, tin oxide on a glass substrate. The next layer
is P-type cadmium telluride; though, N-type or intrinsic may be used.
These two layers constitute the NP junction. A P+ (heavy
P-type) layer of lead telluride aids in
establishing a low resistance contact. A metal layer makes the final
contact to the lead telluride. These layers may be laid down by vacuum
deposition, chemical vapor deposition (CVD), screen printing,
electrodeposition, or atmospheric pressure chemical vapor deposition
(APCVD) in helium. [KWM]




A variation of cadmium telluride is mercury
cadmium telluride. Having lower bulk resistance and lower contact
resistance improves efficiency over cadmium telluride.







Cadmium Indium Gallium diSelenide solar cell (CIGS)



Cadmium Indium Gallium diSelenide: A most promising thin film
solar cell at this time (2007) is manufactured on a ten inch wide roll of flexible polyimide– Cadmium Indium Gallium
diSelenide (CIGS). It has a spectacular efficiency of
10%. Though, commercial grade crystalline silicon cells surpassed this
decades ago, CIGS should be cost competitive. The deposition processes
are at a low enough temperature to use a polyimide polymer as a
substrate instead of metal or glass.
(Figure
above) The CIGS is manufactured in a roll to roll process, which
should drive down costs. GIGS cells may also be produced by an
inherently low cost electrochemical process. [EET]




  • REVIEW:
  • Most solar cells are silicon single crystal or multicrystal because
    of their good efficiency and moderate
    cost.
  • Less efficient thin films of various
    amorphous or polycrystalline materials comprise the rest of the market.
  • Table
    below compares selected solar cells.





Solar cell properties

Solar cell typeMaximum efficiencyPractical efficiencyNotes
Selenium, polycrystalline0.7%-1883,
Charles Fritts
Silicon, single crystal-4%1950's, first
silicon solar cell
Silicon, single crystal PERL, terrestrial, space25%-solar
cars, cost=100x commercial
Silicon, single crystal, commercial terrestrial24%14-17%$5-$10/peak
watt
Cypress Semiconductor, Sunpower, silicon single crystal21.5%19%all
contacts on cell back
Gallium Indium Phosphide/ Gallium Arsenide/ Germanium, single
crystal, multilayer
-32%Preferred for space.
Advanced terrestrial version of above.-40.7%Uses
optical concentrator.
Silicon, multicrystalline18.5%15.5%-
Thin films, ---
Silicon, amorphous13%5-7%Degrades in sun
light. Good indoors for calculators or cloudy outdoors.
Cadmium telluride, polycrystalline16%-glass
or metal substrate
Copper indium arsenide diselenide, polycrystalline18%10%10
inch flexible polymer web. [NTH]
Organic polymer, 100% plastic4.5%-R&D
project











Varicap or varactor diodes










A variable capacitance diode is known as a varicap
diode
or as a varactor. If a diode is reverse biased, an insulating depletion
region forms between the two semiconductive layers. In many diodes the
width of the depletion region may be
changed by varying the reverse bias. This varies the capacitance. This
effect is accentuated in varicap diodes. The schematic symbols is shown
in Figure
below, one of which is packaged as
common cathode dual diode.





Varicap diode: Capacitance varies
with reverse bias. This varies the frequency of
a resonant network.



If a varicap diode is part of a resonant circuit as in Figure
above, the frequency my be varied with a control voltage, Vcontrol.
A large capacitance, low Xc, in series with the varicap
prevents Vcontrol from being shorted out by inductor L. As
long as the series capacitor is large, it has minimal effect on the
frequency of resonant circuit. Coptional
may be used to set the center resonant frequency. Vcontrol
can then vary the frequency about this point. Note that the required
active circuitry to make the resonant network oscillate is not shown.
For an example of a varicap diode tuned AM radio receiver see “electronic
varicap diode tuning,” Ch
9




Some varicap diodes may be referred to as abrupt, hyperabrupt, or super
hyper abrupt. These refer to the change in junction capacitance with
changing reverse bias as being abrupt or hyper-abrupt, or super
hyperabrupt. These diodes offer a relatively large change in
capacitance. This is useful when oscillators or filters are swept over a
large frequency range. Varying the bias of
abrupt varicaps over the rated limits, changes capacitance by a 4:1
ratio, hyperabrupt by 10:1, super hyperabrupt by 20:1.


Varactor diodes may be used in frequency multiplier circuits. See
“Practical analog semiconductor circuits,” Varactor
multiplier




Snap diode







The snap diode, also known as the step
recovery diode
is designed for use in
high ratio frequency multipliers up to 20 gHz. When the diode is forward biased, charge is stored in the
PN junction. This charge is drawn out as the diode
is reverse biased. The diode looks like a
low impedance current source during forward bias. When reverse bias is
applied it still looks like a low impedance source until all the charge
is withdrawn. It then “snaps” to a high impedance state causing a
voltage impulse, rich in harmonics. An applications is a comb generator,
a generator of many harmonics. Moderate
power 2x and 4x multipliers are another application.










PIN diodes






A PIN diode is a fast low
capacitance switching diode. Do not confuse
a PIN switching diode with a PIN photo diode here.
A PIN diode is manufactured like a silicon
switching diode with an intrinsic region
added between the PN junction layers. This yields a thicker depletion
region, the insulating layer at the junction of
a reverse biased diode. This results in
lower capacitance than a reverse biased switching diode.





Pin diode: Cross section aligned with
schematic symbol.



PIN diodes are used in place of switching
diodes in radio frequency (RF) applications, for example, a T/R switch here.
The 1n4007 1000 V, 1 A general purpose
power diode is reported to be useable as a
PIN switching diode. The high voltage
rating of this diode
is achieved by the inclusion of an
intrinsic layer dividing the PN junction.

This intrinsic layer makes the 1n4007 a PIN diode.
Another PIN diode application is a the
antenna switch here
for a direction finder receiver.


PIN diodes serve as variable resistors when the forward bias is varied.
One such application is the voltage variable attenuator here.
The low capacitance characteristic of PIN
diodes, extends the frequency flat response of
the attenuator to microwave frequencies.










IMPATT diode






IMPact Avalanche Transit Time diode
is a high power radio frequency (RF) generator operating from 3 to 100
gHz. IMPATT diodes are fabricated from silicon, gallium arsenide, or
silicon carbide.



An IMPATT diode is reverse biased above
the breakdown voltage. The high doping levels produce a thin depletion
region. The resulting high electric field rapidly accelerates carriers
which free other carriers in collisions with the crystal lattice. Holes
are swept into the P+ region. Electrons drift toward the N
regions. The cascading effect creates an avalanche current which
increases even as voltage across the junction decreases. The pulses of current lag the voltage peak across the
junction. A “negative resistance” effect in conjunction with a resonant
circuit produces oscillations at high power levels (high for
semiconductors).





IMPATT diode: Oscillator circuit and
heavily doped P and N layers.



The resonant circuit in the schematic diagram of
Figure
above is the lumped circuit equivalent of
a waveguide section, where the IMPATT diode
is mounted. DC reverse bias is applied through a choke which keeps RF
from being lost in the bias supply. This may be a section of waveguide known as a bias Tee. Low power RADAR
transmitters may use an IMPATT diode as a
power source. They are too noisy for use in the receiver. [YMCW]





Gunn diode


Diode, gunn
Gunn diode


A gunn diode is solely composed of N-type semiconductor. As such, it is not a
true diode. Figure
below shows a lightly doped N- layer surrounded by
heavily doped N+ layers. A voltage applied across the N-type
gallium arsenide gunn diode creates a
strong electric field across the lightly doped N- layer.





Gunn diode: Oscillator circuit and
cross section of only N-type semiconductor diode.



As voltage is increased, conduction increases due to electrons in a low
energy conduction band. As voltage is increased beyond the threshold of approximately 1 V, electrons move from the
lower conduction band to the higher energy conduction band where they no
longer contribute to conduction. In other words, as voltage increases,
current decreases, a negative resistance condition. The oscillation
frequency is determined by the transit time of
the conduction electrons, which is inversely related to the thickness of the N- layer.



The frequency may be controlled to some extent by embedding the gunn diode into a resonant circuit. The lumped
circuit equivalent shown in Figure
above is actually a coaxial transmission line or waveguide. Gallium
arsenide gunn diodes are available for operation from 10 to 200 gHz at 5
to 65 mw power. Gunn diodes may also serve as amplifiers. [CHW]

[IAP]








Shockley diode




The Shockley diodeis a 4-layer
thyristor used to trigger larger thyristors. It only conducts in one
direction when triggered by a voltage exceeding the breakover voltage,
about 20 V. See “Thyristors,” The
Shockley Diode.

The bidirectional version is called a diac. See “Thyristors,” The
DIAC.







Constant-current diodes








A constant-current diode, also known
as a current-limiting diode, or current-regulating
diode
, does exactly what its name
implies: it regulates current through it to some maximum level. The
constant current diode is a two terminal
version of a JFET. If we try to force more
current through a constant-current diode
than its current-regulation point, it simply “fights back” by dropping
more voltage. If we were to build the circuit in Figure
below(a)

and plot diode current against diode voltage, we'd get a graph that rises at
first and then levels off at the current regulation point as in Figure
below(b).





Constant current diode: (a) Test
circuit, (b) current vs voltage characteristic.



One application for a constant-current diode
is to automatically limit current through an LED or laser diode over a wide range of
power supply voltages as in Figure
below.


Of course, the constant-current diode's regulation point should be chosen to
match the LED or laser diode's optimum
forward current. This is especially important for the laser diode, not so much for the LED, as regular LEDs
tend to be more tolerant of forward current
variations.


Another application is in the charging of
small secondary-cell batteries, where a constant charging current leads
to predictable charging times. Of course,
large secondary-cell battery banks might also benefit from
constant-current charging, but constant-current diodes tend to be very
small devices, limited to regulating currents in the milliamp range.

_________________

الكلام الحلو ما يطلع الا ليها
مصر بلد الامان والرب حاميها
وحارس شبابها وكل مبانيها
مصر بلدنا هتفضل قويه
بيكم يا شبابها هتفضل عفيه
مايفرح فيها عدو ولا بيها
ويموت ونفسو يدوس اراضيها
ويمشى على ترابها يتمنى يرضيها
مصر عمرها اطول من كل ظالم
واللى راح قبلها كان قدامها بيتظاهر
انو عليها قدر وكان كله مظاهر


الرجوع الى أعلى الصفحة اذهب الى الأسفل
شيمو الحو
مهندس جديد
مهندس جديد


عدد الرسائل : 11
العمر : 26
العمل/الترفيه : READING
الـكـلـيـــة : : الهندسة

مُساهمةموضوع: رد: الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......   الإثنين أبريل 05, 2010 6:48 am

الباشمهندسة شيماء شكرا ياباشمهندس على مجهودك العظيم دة وجزاكم الله خيرا والله فى عون العبد مادام العبد فى عون اخيه
الرجوع الى أعلى الصفحة اذهب الى الأسفل
سلمي سالم
مهندس جديد
مهندس جديد


عدد الرسائل : 1
العمر : 26
العمل/الترفيه : غغفغفف
الـكـلـيـــة : : الاولي

مُساهمةموضوع: رد: الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......   الإثنين أبريل 05, 2010 11:40 pm

الف شكر ياهندسه ..... جعله الله في ميزان حسناتك
الرجوع الى أعلى الصفحة اذهب الى الأسفل
tamer ali
مهندس جديد
مهندس جديد


عدد الرسائل : 13
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الـكـلـيـــة : : الهندسة بقنا

مُساهمةموضوع: طلب كتاب فى مادة الpower system   الثلاثاء أبريل 06, 2010 8:28 pm

ممكن طلب صغير اوى من المهندسين المحترمين اوى مهندسين هندسة الازهر
كتاب فى مادة الpower system
اسمه princible of power system
للمؤلف rohit mehata
انا دورت كتير بس موصلتش بس هو اكيد موجود ع النت
tamer ali
الرجوع الى أعلى الصفحة اذهب الى الأسفل
thebest-engineer
مشرف قسم الهندسة الكهربية
مشرف قسم الهندسة الكهربية


عدد الرسائل : 916
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الـكـلـيـــة : : جعلتني مهندسا

مُساهمةموضوع: رد: الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......   الجمعة أبريل 09, 2010 6:28 am

وجزاكي الله خيرا يابشمهندسة شيمو ويابشمهندسة سلمي
مش عارف الباشمهندسة شيمو و شيماء شخص واحد ولا ايه بالظبط
حاسس ان فيه كومينت علي حاجه معينه
عموما
اتمني انها تكون المعلومات المطلوبة
وبالتوفيق للجميع

_________________

الكلام الحلو ما يطلع الا ليها
مصر بلد الامان والرب حاميها
وحارس شبابها وكل مبانيها
مصر بلدنا هتفضل قويه
بيكم يا شبابها هتفضل عفيه
مايفرح فيها عدو ولا بيها
ويموت ونفسو يدوس اراضيها
ويمشى على ترابها يتمنى يرضيها
مصر عمرها اطول من كل ظالم
واللى راح قبلها كان قدامها بيتظاهر
انو عليها قدر وكان كله مظاهر


الرجوع الى أعلى الصفحة اذهب الى الأسفل
thebest-engineer
مشرف قسم الهندسة الكهربية
مشرف قسم الهندسة الكهربية


عدد الرسائل : 916
العمر : 27
العمل/الترفيه : طالب(ولا حول ولاقوة الا بالله)
الـكـلـيـــة : : جعلتني مهندسا

مُساهمةموضوع: رد: الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......   الجمعة أبريل 09, 2010 6:46 am

بشمهندس تامر ان شاء الله الاقي الكتاب لحضرتك وانزلهولك
انت تامر ياهندسة

_________________

الكلام الحلو ما يطلع الا ليها
مصر بلد الامان والرب حاميها
وحارس شبابها وكل مبانيها
مصر بلدنا هتفضل قويه
بيكم يا شبابها هتفضل عفيه
مايفرح فيها عدو ولا بيها
ويموت ونفسو يدوس اراضيها
ويمشى على ترابها يتمنى يرضيها
مصر عمرها اطول من كل ظالم
واللى راح قبلها كان قدامها بيتظاهر
انو عليها قدر وكان كله مظاهر


الرجوع الى أعلى الصفحة اذهب الى الأسفل
thebest-engineer
مشرف قسم الهندسة الكهربية
مشرف قسم الهندسة الكهربية


عدد الرسائل : 916
العمر : 27
العمل/الترفيه : طالب(ولا حول ولاقوة الا بالله)
الـكـلـيـــة : : جعلتني مهندسا

مُساهمةموضوع: رد: الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......   الجمعة أبريل 09, 2010 8:44 am

اتفضل يابشمهندس تامر
دا الكتاب
بس منه 6 فصول بس
ان شاء الله انزلك الباقي قريب
تكون انت ذاكرت دول
هههههههههههه
بالنجاح ياهندسة

ودا رابط التحميل
http://www.mediafire.com/?aktmwtmdj2y

_________________

الكلام الحلو ما يطلع الا ليها
مصر بلد الامان والرب حاميها
وحارس شبابها وكل مبانيها
مصر بلدنا هتفضل قويه
بيكم يا شبابها هتفضل عفيه
مايفرح فيها عدو ولا بيها
ويموت ونفسو يدوس اراضيها
ويمشى على ترابها يتمنى يرضيها
مصر عمرها اطول من كل ظالم
واللى راح قبلها كان قدامها بيتظاهر
انو عليها قدر وكان كله مظاهر


الرجوع الى أعلى الصفحة اذهب الى الأسفل
tamer ali
مهندس جديد
مهندس جديد


عدد الرسائل : 13
العمر : 27
العمل/الترفيه : مهندس كهربا باور ان شاء الله بالسد العالى
الـكـلـيـــة : : الهندسة بقنا

مُساهمةموضوع: رد: الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......   الجمعة أبريل 09, 2010 8:07 pm

الف شكر يا باش مهندس والله مش عارف اقلك ايه بس للاسف احنا ابتدينا فى الكتاب من ال
chapter 7
فانا عاوز ال7و8و9و10و11و12
ده لو فيها تعب يعنى
على فكرة chapter 7
بيتكلم عن supply systems
الرجوع الى أعلى الصفحة اذهب الى الأسفل
tamer ali
مهندس جديد
مهندس جديد


عدد الرسائل : 13
العمر : 27
العمل/الترفيه : مهندس كهربا باور ان شاء الله بالسد العالى
الـكـلـيـــة : : الهندسة بقنا

مُساهمةموضوع: رد: الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......   الجمعة أبريل 09, 2010 8:10 pm

وانتو بتوع تانية بور القاهرة بتاخدوا الماده دى من اى مرجع ومين فى الدكترة بيدهلكم
الرجوع الى أعلى الصفحة اذهب الى الأسفل
thebest-engineer
مشرف قسم الهندسة الكهربية
مشرف قسم الهندسة الكهربية


عدد الرسائل : 916
العمر : 27
العمل/الترفيه : طالب(ولا حول ولاقوة الا بالله)
الـكـلـيـــة : : جعلتني مهندسا

مُساهمةموضوع: رد: الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......   الجمعة أبريل 09, 2010 9:32 pm

ماشي ياهندسة بالليل ان شاء الله انزلك باقي الكتاب
احنا بناخد من مرجع اسمه
power system analysis
دا لواحد اسمه ستيفنسون
هو كتاب كويس برده
وبيدينا المادة دكتورين
الدكتور الجزار والدكتور سيد ناجي

_________________

الكلام الحلو ما يطلع الا ليها
مصر بلد الامان والرب حاميها
وحارس شبابها وكل مبانيها
مصر بلدنا هتفضل قويه
بيكم يا شبابها هتفضل عفيه
مايفرح فيها عدو ولا بيها
ويموت ونفسو يدوس اراضيها
ويمشى على ترابها يتمنى يرضيها
مصر عمرها اطول من كل ظالم
واللى راح قبلها كان قدامها بيتظاهر
انو عليها قدر وكان كله مظاهر


الرجوع الى أعلى الصفحة اذهب الى الأسفل
thebest-engineer
مشرف قسم الهندسة الكهربية
مشرف قسم الهندسة الكهربية


عدد الرسائل : 916
العمر : 27
العمل/الترفيه : طالب(ولا حول ولاقوة الا بالله)
الـكـلـيـــة : : جعلتني مهندسا

مُساهمةموضوع: رد: الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......   السبت أبريل 10, 2010 6:07 am

ودا ياهندسة رابط للكتاب كله
من فصل 1 لفصل 11
ربنا معاك ياكبير


http://www.mediafire.com/?wdzaolonmgh

_________________

الكلام الحلو ما يطلع الا ليها
مصر بلد الامان والرب حاميها
وحارس شبابها وكل مبانيها
مصر بلدنا هتفضل قويه
بيكم يا شبابها هتفضل عفيه
مايفرح فيها عدو ولا بيها
ويموت ونفسو يدوس اراضيها
ويمشى على ترابها يتمنى يرضيها
مصر عمرها اطول من كل ظالم
واللى راح قبلها كان قدامها بيتظاهر
انو عليها قدر وكان كله مظاهر


الرجوع الى أعلى الصفحة اذهب الى الأسفل
شيمو الحو
مهندس جديد
مهندس جديد


عدد الرسائل : 11
العمر : 26
العمل/الترفيه : READING
الـكـلـيـــة : : الهندسة

مُساهمةموضوع: رد: الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......   السبت أبريل 10, 2010 4:51 pm

ايو ياهندسة شيمو وشيماء واحد لكنى فى التسجيل الاول نسيت كلمة السر فسجلت مرة تانية بشيمو المهم من فضلك ممكن حضرتك تنزلى شبتر1&2 فى مادة نظرية الماكينات من كتاب اسمه material of macheins
الرجوع الى أعلى الصفحة اذهب الى الأسفل
thebest-engineer
مشرف قسم الهندسة الكهربية
مشرف قسم الهندسة الكهربية


عدد الرسائل : 916
العمر : 27
العمل/الترفيه : طالب(ولا حول ولاقوة الا بالله)
الـكـلـيـــة : : جعلتني مهندسا

مُساهمةموضوع: رد: الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......   السبت أبريل 10, 2010 7:30 pm

اوك يابشمهندسة
ممكن بس حضرتك تتاكدي من اسم الكتاب والمؤلف
وان شاء الله الاقيه
احنا اخدنا منه السنه اللي فاتت
بس مش فاكر اسم المؤلف

_________________

الكلام الحلو ما يطلع الا ليها
مصر بلد الامان والرب حاميها
وحارس شبابها وكل مبانيها
مصر بلدنا هتفضل قويه
بيكم يا شبابها هتفضل عفيه
مايفرح فيها عدو ولا بيها
ويموت ونفسو يدوس اراضيها
ويمشى على ترابها يتمنى يرضيها
مصر عمرها اطول من كل ظالم
واللى راح قبلها كان قدامها بيتظاهر
انو عليها قدر وكان كله مظاهر


الرجوع الى أعلى الصفحة اذهب الى الأسفل
tamer ali
مهندس جديد
مهندس جديد


عدد الرسائل : 13
العمر : 27
العمل/الترفيه : مهندس كهربا باور ان شاء الله بالسد العالى
الـكـلـيـــة : : الهندسة بقنا

مُساهمةموضوع: رد: الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......   الخميس أبريل 15, 2010 5:25 pm

الف شكر يا باش مهندس
بصراحه الف قليل وانا بصراحه نفسى اتعرف على حضرتك
الرجوع الى أعلى الصفحة اذهب الى الأسفل
thebest-engineer
مشرف قسم الهندسة الكهربية
مشرف قسم الهندسة الكهربية


عدد الرسائل : 916
العمر : 27
العمل/الترفيه : طالب(ولا حول ولاقوة الا بالله)
الـكـلـيـــة : : جعلتني مهندسا

مُساهمةموضوع: رد: الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......   الخميس أبريل 15, 2010 11:02 pm

شكر ايه بس ياهندسة
احنا اخوات
وانا ليا الشرف اني اتعرف علي حضرتك
بس الادارة مانعين الرسايل الخاصة
ان شاء الله هنتواصل بطريقة او باخري
عموما فيه بعض مواضيع انا منزلها هتلاقي في الملفات المرفقه الميل بتاعي

_________________

الكلام الحلو ما يطلع الا ليها
مصر بلد الامان والرب حاميها
وحارس شبابها وكل مبانيها
مصر بلدنا هتفضل قويه
بيكم يا شبابها هتفضل عفيه
مايفرح فيها عدو ولا بيها
ويموت ونفسو يدوس اراضيها
ويمشى على ترابها يتمنى يرضيها
مصر عمرها اطول من كل ظالم
واللى راح قبلها كان قدامها بيتظاهر
انو عليها قدر وكان كله مظاهر


الرجوع الى أعلى الصفحة اذهب الى الأسفل
الهواري
مراقب عام على اقسام المنتدى
مراقب عام على اقسام المنتدى


عدد الرسائل : 1357
العمر : 27
العمل/الترفيه : طالب
الـكـلـيـــة : : الهندسة

مُساهمةموضوع: رد: الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......   الجمعة أبريل 16, 2010 5:24 am

مجهوداتك ياباشمهندس احمد جامده بجد من غير اي مجامله
ربنا يتقبل منك النية الصادقة ويجعل عملك في ميزان حسناتك
علي فكره ياباشمهندسين الرسايل الخاصة مقفوله فعلا بس اي حد ممكن يطلب ايميل اي حد من الادارة للتعارف والافاده وده عن طريق ايميل المنتدي الرسمي مش ف المنتدي حفاظا علي خصوصية بيانات وايميلات الاعضاء
الرجوع الى أعلى الصفحة اذهب الى الأسفل
شيمو الحو
مهندس جديد
مهندس جديد


عدد الرسائل : 11
العمر : 26
العمل/الترفيه : READING
الـكـلـيـــة : : الهندسة

مُساهمةموضوع: رد: الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......   السبت أبريل 24, 2010 1:41 am

ممكن ياباشمهندسين ممكن تفيدونى فى مادة نظرية الماكينات
الرجوع الى أعلى الصفحة اذهب الى الأسفل
thebest-engineer
مشرف قسم الهندسة الكهربية
مشرف قسم الهندسة الكهربية


عدد الرسائل : 916
العمر : 27
العمل/الترفيه : طالب(ولا حول ولاقوة الا بالله)
الـكـلـيـــة : : جعلتني مهندسا

مُساهمةموضوع: رد: الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......   السبت أبريل 24, 2010 4:12 am

مين بيديكي المادة دي يابشمهندسة
هما كانو دكتورين بيدو البنين
واحد تقريبا اسمه تامر تخين كده واسمراني ومربي دقنه خفيف
وواحد تاني صوته عالي ومزعج
مع احترامي لكل الناس اللي في ميكانيكا
شوفي يابشمهندسة مش تخافي من المادة دي خالص
لو هما نفس الدكاترة
يبقي الراجل بتاع الصوت العالي هيديكو شيت مش هيخرج منه الامتحان وكمان هيحله ليكم
اما التاني الاسمراني ده فهيجيب من الامثله اللي هو حلها في المحاضرات ومش هيخرج عنها
وكمان امتحان اعمال السنه كله هيكون في امتحان الفاينال
يعني تحلي اعمال السنه
تذاكري 20 او 25 مساله اللي هما هيشرحوهم ويحلوهم
كده ضمنتي تقدير في الماده
ونصيحة مني
ركزي علي المواد اللي من 200 درجه زي المعمل والالكترونكس عشان هي دي اللي هترفعلك التقدير
مش معني كده انك تهملي المواد التانية
لا طبعا انتي عندك مثلا الانجليش والهندسة المدنية دول استحالة تضيعي منهم الامتياز
يعني لو حد في مدني شرحلك الهندسة المدنية يبقي ضمنتي الامتياز
اللي هيكون امتحانه صعب الدكتور محمد مهنا انا عرفت ان هو اللي بيديكو سيركت
هو رخم بس مش بيسقط حد حاولي تكتبيله كل اللي انتي عارفاه ومش تبخلي باي معلومه مهما كانت صغيرة ليه هو بالذات وفي كل المواد
وربنا معاكي ويوفقك انتي والمسلمين

_________________

الكلام الحلو ما يطلع الا ليها
مصر بلد الامان والرب حاميها
وحارس شبابها وكل مبانيها
مصر بلدنا هتفضل قويه
بيكم يا شبابها هتفضل عفيه
مايفرح فيها عدو ولا بيها
ويموت ونفسو يدوس اراضيها
ويمشى على ترابها يتمنى يرضيها
مصر عمرها اطول من كل ظالم
واللى راح قبلها كان قدامها بيتظاهر
انو عليها قدر وكان كله مظاهر


الرجوع الى أعلى الصفحة اذهب الى الأسفل
شيمو الحو
مهندس جديد
مهندس جديد


عدد الرسائل : 11
العمر : 26
العمل/الترفيه : READING
الـكـلـيـــة : : الهندسة

مُساهمةموضوع: رد: الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......   السبت أبريل 24, 2010 4:34 am

جزاكم الله خيرا ياهندسة بس انا خايفه جدا لان هندسة بصراحة مثل السهل الممتنع الواحد شايفها سهلة بس يجى يحل الله المستعان فى الامتحانات وشكرا على ردك ياهندسة
الرجوع الى أعلى الصفحة اذهب الى الأسفل
thebest-engineer
مشرف قسم الهندسة الكهربية
مشرف قسم الهندسة الكهربية


عدد الرسائل : 916
العمر : 27
العمل/الترفيه : طالب(ولا حول ولاقوة الا بالله)
الـكـلـيـــة : : جعلتني مهندسا

مُساهمةموضوع: رد: الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......   السبت أبريل 24, 2010 4:49 am

ان شاء الله خير ياهندسة
كله كده في الكلية
ربنا يسترها معانا جميعا
انا والله لسة مش عارف اذاكر حاجه
حاسس ان المواد متلخبطه مع بعضها
بس دا احساس كل سنه وفي الاخر ربنا بيسترها من عنده والله
لو علي اعمالنا يبقي مش هننجح
فربنا يسترها السنه دي كمان

_________________

الكلام الحلو ما يطلع الا ليها
مصر بلد الامان والرب حاميها
وحارس شبابها وكل مبانيها
مصر بلدنا هتفضل قويه
بيكم يا شبابها هتفضل عفيه
مايفرح فيها عدو ولا بيها
ويموت ونفسو يدوس اراضيها
ويمشى على ترابها يتمنى يرضيها
مصر عمرها اطول من كل ظالم
واللى راح قبلها كان قدامها بيتظاهر
انو عليها قدر وكان كله مظاهر


الرجوع الى أعلى الصفحة اذهب الى الأسفل
شيمو الحو
مهندس جديد
مهندس جديد


عدد الرسائل : 11
العمر : 26
العمل/الترفيه : READING
الـكـلـيـــة : : الهندسة

مُساهمةموضوع: رد: الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......   السبت أبريل 24, 2010 5:24 am

شكرا على ردك ياهندسة
الرجوع الى أعلى الصفحة اذهب الى الأسفل
 
الي من قرر دخول قسم الهندسة الكهربية ؟.....ادخل واسأل؟......
استعرض الموضوع السابق استعرض الموضوع التالي الرجوع الى أعلى الصفحة 
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