Showing posts with label components. Show all posts
Showing posts with label components. Show all posts
A photodiode is a type of photo detector capable of converting light into either current or voltage, depending upon the mode of operation.Photo diodes are similar to regular semiconductor diodes except that they may be either exposed or packaged with a window or optical fiber connection to allow light to reach the sensitive part of the device. Many diodes designed for use specifically as a photo diode will also use a PIN junction rather than the typical PN junction.
Working:-
A photodiode is a PN junction or PIN structure. When a photon of sufficient energy strikes the diode, it excites an electron, thereby creating a free electron and a (positively charged electron hole). This mechanism is also known as the photoelectric effect. If the absorption occurs in the junction's depletion region, or one diffusion length away from it, these carriers are swept from the junction by the built-in field of the depletion region. Thus holes move toward the anode, and electrons toward the cathode, and a photo current is produced. This photocurrent is the sum of both the dark current (without light) and the light current, so the dark current must be minimised to enhance the sensitivity of the device.
1)P-N photodiodes are used in similar applications to other photo detectors.
2)Photo diodes are used in consumer electronics devices such as compact disc players, smoke detectors, and
4)PIN diodes are much faster and more sensitive than ordinary p-n junction diodes, and hence are often used
5)P-N photodiodes are not used to measure extremely low light intensities. Instead, if high sensitivity is
Applications:
2)Photo diodes are used in consumer electronics devices such as compact disc players, smoke detectors, and
the receivers for remote controls in VCR's and televisions.
3)In other consumer items such as camera light meters, clock radios (the ones that dim the display when it's
3)In other consumer items such as camera light meters, clock radios (the ones that dim the display when it's
dark).
4)PIN diodes are much faster and more sensitive than ordinary p-n junction diodes, and hence are often used
for optical communications and in lighting regulation.
5)P-N photodiodes are not used to measure extremely low light intensities. Instead, if high sensitivity is
needed, avalanche photo diodes,intensified charge-coupled devices or photomultiplier tubes are used for
applications such as astronomy, spectroscopy, night vision equipment and laser rangefinding.
Hai frndz we all know that till now plastic is used as insulator due to their poor conductivity..
But it is found that in future these plastics will be used as conductors.Scientists claim to have found a new type of plastic which conduct electricity..!
A team of scientists placed a thin film of metal on the plastic sheet and then mixed it with a polymer surface using an ion beam.The resulted
material was found to conduct electricity..! Prof Paul Meredith of University of Queensland told that “What the team has been able to do here is use an ion beam to tune the properties of a plastic film so that it conducts electricity like the metals used in the electrical wires themselves, and even to act as a superconductor and pass electric current without resistance if cooled to low enough temperature.”
The new material formed is stronger, flexible and a cheap conducting plastic film.
The use of plastic has banned by the government due to the difficulty in its disposal, this newely invented plastic might further increase that problem..!
Please write ur valuable comments..!
Hai frndz now i am going to tell u about an intresting matter..
Everyone knows that for every transistor there is a junction between the two sandwitched regions..
BUT
The scientists from ireland-based Tyndall national institute has undergone some researches and have done the worlds first junctionless transistor..
On a single microprocessor, there are approximately two billion transistors, so advances in the structure and manufacturability of transistors are significant..
The team has succeeded in making it at 50 nanometres, which is 20 times smaller than the transistors that were initially published in Nature Nanotechnology.
Due to demand in features of electronic devices had made the manufacturers to pack more features into the electronic devices..
The newly built junctionless transistor is said to be 30% more energy efficient than the transistor which has junction..And this transistor has some different characteristics compared to previous..
U can just watch this video so that u can understand this topic better..
Here is the video by Prof.Roger..
Please write your valuable comments..
Please write your valuable comments..
Soldering:
Soldering is a process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, the filler metal having a relatively low melting point. Soft soldering is characterized by the melting point of the filler metal, which is below 400 °C (752 °F).[1]
The filler metal used in the process is called solder.
Soldering is distinguished from brazing by use of a lower melting-temperature filler metal. The filler metals are typically alloys that have liquidus temperatures below 350°C. It is distinguished fromwelding by the base metals not being melted during the joining process which may or may not include the addition of a filler metal.[2] In a soldering process, heat is applied to the parts to be joined, causing the solder to melt and be drawn into the joint by capillary action and to bond to the materials to be joined by wetting action. After the metal cools, the resulting joints are not as strong as the base metal, but have adequate strength, electrical conductivity, and water-tightness for many uses. There is evidence that it was employed up to 5000 years ago in Mesopotamia.[3]
Deaoldring:
n electronics, desoldering is the removal of solder and components from a circuit for troubleshooting, for repair purposes, component replacement, and to salvage components. Electronic components are often mounted on a circuit board, and it is usually desirable to avoid damaging the circuit board, surrounding components, and the component being removed.
Soldering is distinguished from brazing by use of a lower melting-temperature filler metal. The filler metals are typically alloys that have liquidus temperatures below 350°C. It is distinguished fromwelding by the base metals not being melted during the joining process which may or may not include the addition of a filler metal.[2] In a soldering process, heat is applied to the parts to be joined, causing the solder to melt and be drawn into the joint by capillary action and to bond to the materials to be joined by wetting action. After the metal cools, the resulting joints are not as strong as the base metal, but have adequate strength, electrical conductivity, and water-tightness for many uses. There is evidence that it was employed up to 5000 years ago in Mesopotamia.[3]
Deaoldring:
n electronics, desoldering is the removal of solder and components from a circuit for troubleshooting, for repair purposes, component replacement, and to salvage components. Electronic components are often mounted on a circuit board, and it is usually desirable to avoid damaging the circuit board, surrounding components, and the component being removed.
A digital multimeter is one the most versatile and useful instruments in your auto shop. It is important to own a good model and understand how to use it properly. A digital multimeter is actually three devices in one. It is a voltmeter that measure electrical potential across a device in volts.It is an ammeter that measures the amount of electric current through a device. This is measured in amps. Finally, a digital multimeter is an ohmmeter that measures electrical resistance of a device. Electrical resistance is measured in ohms.
Today, modern digital multimeters are designed to be rugged and easy to operate. A good multimeter will have a rugged plastic case and large, easy to use selector knobs. The top part contains the digital read out screen. This is something you should thoroughly check out before you purchase one. Make sure the screen is large enough to read it and make sure you see the readout in sunlight. Chances are you will be using this instrument outside in direct sunlight.
Below the digital readout is a large knob called the function switch. The function switch allows you to change the modes the digital multimeter operates in. For example, you can easily change from voltmeter to ammeter to ohmmeter with the turn of the dial. Again make sure the function switch is large and easy to operate. Most function switches have approximately eight positions. Most have three V markings that measure voltage. They measure AC, DC and low voltage currents in the millivolt range. Next there will be two positions marked with A~ and A=. The A~ measures AC current in amps and the A= measures DC current in amps. The upside down horseshoe Ω measures resistance in ohms.
In order to measure voltage, first turn on the digital multimeter and let it go through its startup procedure. Generally the digital readout lights up and the unit goes through its self diagnostic checkout. Once that is completed you are ready to measure volts. Now turn the function switch to V= to measure DC volts. Now you will need to connect the red and black leads to the digital multimeter. Connect the red lead to the red input terminal labeled VΩ and connect the black lead to the terminal labeled COM for common terminal. Now you can measure volts by putting the red lead on the terminal with the higher potential and the black lead on the lower one.
To measure amps, the leads must be connected in a different fashion. First set the function switch to A= position. Connect the black lead to the COM terminal. Now you must connect the red lead to the terminal labeled 300mA. Now you are ready to connect the meter in series the device being measured by opening up the circuit and inserting the meter between the open points. The results will be in milliamps because you are using the 300mA terminal.
The third feature of a digital multimeter is its ability to measure to Ohms. Ohms is a measurement of resistance in an electrical circuit. First disconnect all wiring and power sources from the device being measured. Now turn the function switch to the Ω position and connect your leads. The red lead is connected to the terminal labeled VΩ and the black terminal connects to the COM terminal. The display will indicate OL. This is normal and means there is an overload. Now connect the leads across the device to measure the Ohms.
These are the basic functions of a digital multimeter. Remember to shut off your multimeter before storing it back in the your toolbox. You do not want a drained battery the next time you will need it. There are several good brands on the market today. Fluke digital multimeters are probably the most popular and you won't go wrong with one.
A bipolar (junction) transistor (BJT) is a three-terminal electronic device constructed of
doped semiconductor material and may be used in amplifying or switching applications.
Bipolar transistors are so named because their operation involves both electrons and
holes. Charge flow in a BJT is due to bidirectional diffusion of charge carriers across
a junction between two regions of different charge concentrations.
This mode of operation
is contrasted with unipolar transistors, such as field-effect transistors, in which only one
carrier type is involved in charge flow due to drift. By design, most of the BJT collector
current is due to the flow of charges injected from a high-concentration emitter into the
base where they are minority carriers that diffuse toward the collector, and so BJTs are
classified as minority-carrier devices.
An NPN transistor can be considered as twodiodes with a shared anode. In typical operation
, the base-emitter junction is forward biased and the base–collector junction is reverse
biased. In an NPN transistor, for example, when a positive voltage is applied to the
base–emitter junction, the equilibrium between thermally generatedcarriers and the repelling
electric field of thedepletion region becomes unbalanced, allowing thermally excited electrons
to inject into the base region. These electrons wander (or "diffuse") through the base from
the region of high concentration near the emitter towards the region of low concentration near
the collector. The electrons in the base are called minority carriersbecause the base is
doped p-type which would make holes the majority carrier in the base.
To minimize the percentage of carriers that recombine before reaching the collector–base
junction, the transistor's base region must be thin enough that carriers can diffuse across
it in much less time than the semiconductor's minority carrier lifetime. In particular, the
thickness of the base must be much less than the diffusion length of the electrons. The
collector–base junction is reverse-biased, and so little electron injection occurs from the
collector to the base, but electrons that diffuse through the base towards the collector are
swept into the collector by the electric field in the depletion region of the collector–base
junction. The thin shared base and asymmetric collector–emitter doping is what differentiates
a bipolar transistor from two separate and oppositely biased diodes connected in series.
A Zener diode is a type of diode that permits current not only in the forward direction like
a normal diode, but also in the reverse direction if the voltage is larger than the breakdown
a normal diode, but also in the reverse direction if the voltage is larger than the breakdown
voltage known as "Zener kneevoltage" or "Zener voltage". The device was named after
Clarence Zener, who discovered this electrical property.
A conventional solid-state diode will not allow significant current if it is reverse-biased
below its reverse breakdown voltage. When the reverse bias breakdown voltage is exceeded
, a conventional diode is subject to high current due to avalanche breakdown. Unless this
current is limited by circuitry, the diode will be permanently damaged due to overheating.
In case of large forward bias (current in the direction of the arrow), the diode exhibits a
voltage drop due to its junction built-in voltage and internal resistance. The amount of the
voltage drop depends on the semiconductor material and the doping concentrations.
A Zener diode exhibits almost the same properties, except the device is specially
designed so as to have a greatly reduced breakdown voltage, the so-called Zener voltage.
By contrast with the conventionaldevice, a reverse-biased Zener diode will exhibit a
controlled breakdown and allow the current to keep the voltage across the Zener diode
close to the Zener voltage. For example, a diode with a Zener breakdown voltage of 3.2 V
will exhibit a voltage drop of very nearly 3.2 V across a wide range of reversecurrents.
The Zener diode is therefore ideal for applications such as the generation of a reference
voltageor as a voltage stabilizer for low-current applications.
The Zener diode is mainly made of heavely dooped with impurities.
Another mechanism that produces a similar effect is the avalanche effect as in the
avalanche diode. Thetwo types of diode are in fact constructed the same way and
both effects are present in diodes of this type. In silicon diodes up to about 5.6 volts
, the Zener effect is the predominant effect and shows a marked negative temperature
coefficient. Above 5.6 volts, the avalanche effect becomes predominant andexhibits
a positive temperature coefficient[1]. In a 5.6 V diode, the two effects occur together
and their temperature coefficients neatly cancel each other out, thus the 5.6 V diode
is the component of choicein temperature-critical applications. Modern manufacturing
techniques have produced devices with voltageslower than 5.6 V with negligible
temperature coefficients, but as higher voltage devices are encountered,the temperature
coefficient rises dramatically. A 75 V diode
has 10 times the coefficient of a 12 V diode.
The V-I characteristics of Zener Diode will be like:
All such diodes, regardless of breakdown voltage, are usually marketed under the umbrella term of
"Zener diode".
Resistor is the most basic electrical and electronic component, used in
electrical and electronic circuts.It is a passive but most important element.
Applications:A Resistor find many applications in electrical and electronic
circuts.It is used as
a)an electrical load
b)a current limiting device
c)a potentioal divider
d)a biasing element
e)a filter and timer in combination with capacitor
f)a relay coil in thermal relays
g)volume,brightness and tone controller in Radio and T.V. sets Etc.
Types of Resistors:-
1)Fixed Resistrors:-Resistors designed for a particular value and whose
value cannot be varied as and when required
Based on the method used and the method of construction, fixed Resistors are
further classified into
a)Wire wound resistors(WW Resistors)
b)Carbon composition resistors(CC Resistors)
c)Cracked carbon resistors or carbon film resistors
d)Metal oxide resistors
e)Metal film resistors.
2)Varible resistors:-Varible resistors are those whose resistance value can
be varied continuosly or in steps.They are requried to adjust the value of
current and voltage in electrical and electronic ciruts.
Based on the type of operation, varible resistors are further classified into
a)Continuosly varible resistors
(i)Potentiometers and (ii)Rehostats
b)Adjustable or preset resistors
(i)Decade resistance boxes
(ii)Thermistors
(iii)Varistors
3)A wire wonund resistor having one or more additional terminals along its
length generally for voltage divider applications is called tapped
resistors.
There are two types of tapped resistors they are
(i)Fixed tapped
(ii)Adjustable tapped
Capicator is anelectrical or electronic component which stores electricalenergy in the form of electric charges.Applications of Capacitor:-
a)to store electrical energy
b)to oppose change in the applied voltage
c)to block d.c and allow a.c to pass through it
d)to improve the p.f of a circut
e)to split the phase and start S/ph a.c motor
f)to bypass high frequency signals and block low frequency signals
g)in radio tuning circuts,oscilllators,bypass filters etc.
Types of capacitors:-
1)Fixed capacitors:-Capacitors designed for a particular value and whose
value cannot be varied as and when required.
Based onthe dielectric material used, fixed capacitors are further classified
as follows
(i)Mica capacitors
(ii)Cermic capacitors
(iii)Paper capacitors
(iv)Plastic film capacitors
(v)Electrolytic capacitors.
2)Adjustable capacitors:-A capacitor which is designed to adjust the value
of capacitance is called as adjustable capacitor.
3)Varible capacitor:-Varible Capacitors are those whose resistance value can
be varied continuosly or in steps.
An inductor is an electro-magnetic (coil) which opposes any change in the current flowing through it.It consists of number of turns of fine wire, wound in a spiral or cyclinderical form, to obain concentrated feild parallel
to the axis of the coil.
Applications of Inductors:-
a)Communication circuts
b)Radio and T.V circuts
c)Filter circuts
d)Telemetering equipment
e)Modulation and Demodulation circuts
f)Radar navigation devices
g)Tuning circuts to select the requried signal
h)Fluorescent lamp sets to create surge voltage etc.
Types of inductors
:-
1)Based on the core material used,inductors are classified as
a)Iron cored inductors-used for low frequency
b)Air cored inductors-used at high frequency
c)Powdered iron cored inductors
d)Ferrite cored inductors
e)Varaible inductors
2)Based on the operating frequency they are cllassified as
f)Audio frequency (AF) inductors
g)Radio frequency (RF) inductors.
