TRANSISTOR Disadvantages-MOSFET Advantages

Hi friends,this time i wanna talk about basic electronic devices, they are transistor and mosfet with their disadvantages and advantages respectively. Major disadvantages that i would consider for transistor are,
1.Input impedence
2.Stability
I would also explain how these two are advantages for mosfet.
1.Input impedence : 
For transistor:Any small input at the base terminal will turn transistor active and make it work (i.e as a amplifier or as a switch),which is not required at particular small input. Transistor should respond only to a reasonable input .This indicates the input impedence(Ri) of a transistor is low.Actually for CC based transistor configuration,the input impendence is upto 500k ohms,which is enough, but if transistor is biased then due to R1 and R2 the net input impedence will decrease(R1||R2||Ri).
For mosfet:Mosfet abbreviates metal oxide semiconductor field effect transistor,as the name itself indicates presence of oxide(SiO2) an insulator,which  prevents mosfet not to respond for small inputs
2.Stabilty
For transistor:We desire a fixed operating point that to in active region with Ib,Ic,Vce.The flow of small current(due to low input impedence) into BJT results in dissipation of electrical energy inform of heat.This results in rise of tempoerature which inturn increases Ic0 but Ic=(alpha)IE+Ic0,so Ic also increases.With this operating point is disturbed.It is referred as bias instability.To overcome bias instability,we have bias circuits which will stabilise the Q pont even change occured in Ic0 and temparature.Ic0 increases by 2 times for every 10 degree rise in temperature.
For mosfet:Bais instability is occured in BJT due to low input impedence,but as i said mosfet has high input impedence(due to SiO2) compared to transistor,so chances of instability is less in case of mosfet.

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Circuit which indicates the charging level of battery

Hi friends ,As the need for rechargeable devices are increasing it is necessary to maintain the life of electronic devices which runs with  battery.Life of any rechargeable device depends upon the usage of charging capacity it has.Overcharging leads to reduce the life of device.Now a days due to overcharging many of the devices are out of work field.So if we know proper charging level of battery at every instant of time,it would help us to know whether to charge the battery or to use it.My circuit provides this features i.e when the battery is fully charged we can see a LED light glowing by this one will come to know that the battery is fully charged and has to unplug it.If not it need to be charged. Today i wanna show a circuit which will indicates the charging level of a DC storage battery.

Circuit description:

Input is an alternating voltage signal of 220v and 50hz supply,given to capacitor which is used to block DC,Stepdown transformer to reduce the signal level ,a rectifier to convert AC to DC,inverting and non inverting amplifiers,LED,1 v DC source and the battery whose charging level is to be detected.

Working:

Initially AC signal is passed through 'C' to block DC,which is fed to step down transformer to reduce the voltage signal from 220v to 13v.Now this is given to rectifier circuit for conversion process i.e from AC to DC.This constant 13V is given to non inverting terminal of opamp-1,inverting terminal is given with battery positive terminal for same opamp.Output of opamp-1 is given to inverting terminal of opamp-2 and its non inverting terminal is grounded.Output of opamp-2 is fed to LED which has -1v supply.

Operation:

case:1 Assume initially the battery has 2v in it ,V+>V-,therefore V01 is 13-2=11v,V02=-11v,since the potential at anode is much less than potential at cathode the LED doesnot glow.It means that battery is not yet fully charged.

case:2 Assume now the battery is fully charged i.e upto 13v,V+=V-,therefore V01=0,V02=0 and now the potential at anode(0v) is greater than potential at cathode(-1v),LED glows and indicates us that battery is fully charged and need to be unplugged.

*Since the ouput of rectifer is given to battery,it charges the battery when it is discharged by the user.

*Here two opamp are used,but the same work can be done with single opamp.For better explanation i has shown two.

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WIRELESS ELECTRICITY-EXPLAINED

Movement of electrons (current) in free space without using any proper conduction path between two electronic devices is referred to as wireless electricity.Long before it is a dream but after a few years it will come true.

• Everyone knew that conductor has free valence electrons, by applying proper voltage (nothing but force) these electrons move and results current(flow of electrons).

1.Actually the concept of wireless electricity has started with faraday's law.

It states that whenever a conductor is placed in magnetic field(time changing) an induced emf(electro motive force) or voltage is induced in another conductor.This is considered as base for wireless electricity. Without any proper conduction path,this induced emf will results to move electrons in another conductor.This concept resulted to discover transformer.With the transformer we are able to alter voltage from a high valve(received from station)to a value required for home appliances.This is beginning for wireless electricity.

2.Second thing I would consider is from the basics of antenna. Actually antenna is an interface between free space and transmission line that converts V/I waves into E/H waves at the transmitter and viceversa at the receiver.HOW? When a voltage(V/I) is fed at the input, due to electric field(electrons) and magnetic field(as these electrons are moving),E/H waves are released into medium, this conversion V/I into E/H process is called radiation and at the receiver E/H is converted back  to its V/I form, this process is called induction.

By adopting both radiation and induction techniques we can transmit electricity without proper conduction path between two devices.

Conclusion:From first technique we need a strong magnetic field between two wireless devices and from second technique we need an antenna for wireless transfer of electricity.

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Software's for Win 7 homebasic and Add-on for chrome

Hi friends this time i would like to share two softwares for windows 7 home basic operating system and a Add-on for Chrome browser.
1.Software-"personalization -setupfile"
Every user of win 7 home basic will not find personalize option in the popup menu,but where as in win 7 professional , ultimate and home premium, users can have it with which one can change the wallpaper of desktop by one click.To get the personalize option for home basic ,download a setupfile "personalization" and get installed in your PC.And now you can see personalization option in popup menu.But we have still left out with "next background option",by which wallpaper changes automatically.
2.Screen Shot Add-on-"CLIPULAR"
    For chrome users,Clipular is one of the best screen shot Add-on.When Clipular is added to chrome,one can take screen shot for the tabs s/he has been working on.Screen shots of full screen or else a part can be taken which will be stored in book(Add-on book),for usage of that image(screen shot) one has to login ,save the file and use it.Since it is add-on for chrome one cannot use it outside chrome.Shortcuts are specified ,which ease its usage.
3. Software-"EPICPEN"
    Those who want to draw on screen, to specify a matter to another user. Epicpen software is useful.By using this,one can able to highlight the matter,that s/he is going to convey.By installing this software one can use a pencil,eraser and color selection.But one cannot draw straight lines or a particular shape,only zigzag lines are allowed.The file can be found at http://sourceforge.net/projects/epicpen/

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DISPLAY DEVICES-EXPLAINED

HI friends in this post we are going to learn about the various types of DISPLAY DEVICES which we had been known.In this the foremost one is 

1.CRT(Cathode ray tube):Experiments to discover more on smallest  particle "atom"(on that time)by J.J thomson, landed him to know about electron.In his experiment he noticed that a ray of particles called electrons(named by G.J stoney) were travelling from cathode to anode,he made this electrons to fall on fluorescent screen when this electrons hit the screen bright spot is produced.On their way from electron gun to screen their is chance of deflection, due to surrounding fields(as electrons are negative),to overcome this he placed horizontal and vertical deflection plates in between the space.So based upon the electrons, which hit the screen display is produced.now a days we can observe CRT's in CRO(cathode ray oscilloscope) .Next to this is 
2.LCD(liquid crystal display):Display by liquid crystals.Normally we know crystals in solid form like rochelle salt,quartz etc unlike here it is liquid crystals,means crystals which are in liquid form or in which the  molecules tend to orientate easily.Actually liquid crystals state is in between solids and liquids.As we know that even on slight increase of temperature will turn this liquid into real liquid so liquid crystal  are effected easily by electric current.Based upon this feature, applied electric current results molecules change their orientation with which display is produced.Next to this
3.LED(light emitting diodes):The diodes which emit light when they are forward biased are LED's.when we look at aluminum-gallium-arsenide(AlGaAs), in this type of semiconductor made diodes the interaction between electrons and holes is interesting , which is responsible to emit light.we knew in previous post "introduction to pn junction diode" about diode condition when no external bias is applied i.e  depletion layer is formed(electrons recombine with holes due to diffusion) on recombination electrons jump from lower orbital to higher orbital and vice versa .Electrons lose(release) energy when they jump from higher to lower orbital and needs(gains) energy to move from lower to higher orbital.The energy released in this process is in form of photons which are basic particles of light,these photons have speed and momentum but have no mass.
you can ask me, why this emission of light doesn't occur in normal Si, Ge diode,the reason is that atoms in normal diode are arranged in a manner that energy drop is relatively short which is invisible to normal eye.By release of photons in led's display is produced.Next to this
4.OLED(organic light emitting diodes):The main differences between led and Oled is the presence of organic layer present between anode and cathode of a diode.The organic layers in Oled are organic layer,conducting layer,emissive layers,the main purpose of this layers are to transport much holes from anode and much electrons from cathode, this will increases the recombination rate which in turn increases the emission of photon which are basic particles of light,this is how display is produced in Oled.

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TRANSMISSION MEDIA

Now a days communication is necessary in every field and to communicate a transmission media is needed. Transmission media is classified into two types.

·         Wire communication (a connection between transmitter and receiver.)

·         Wireless communication (no connection between transmitter and receiver.)

1.                                                          In case of wire line communication, nonelectrical signals are converted into electrical signals                         at the entry and these electrical signals(voltage,current) are transmitted with the help of                                   conductor.The device which transforms it is called the “Transducer”

There are 3 major and well known types of wire communication

·         COAXIAL CABLE:

*It is kind of copper cable mostly used by cable tv companies between communicating antenna and user home tv set and is applied by telephone companies from their offices to poles.

*This cable has three layers enclosed in it, inner layer is conducting copper wire and  two outer layers are used to protect the conducting(cu wire) path from outer damages.

*Major disadvantage regarding this cable is electromagnetic induction

HOW? Here it is said that electrical signals are transmitted by inner cu layer ,it means we have electric field and as these electrons are flowing(current) we have magnetic field around the conductor.so both fields exists. whenever another conductor is brought near to it, we may have collision and there is chance of loss of information.

·         TWISTED PAIR:

*To overcome the loss of information in the coaxial cable Twisted pair cable was introduced as name itself indicates pair of wires are twisted one, to collapse electromagnetic interference.

*It is ordinary wire that connects home and many business computers. To reduce  cross talk and electromagnetic induction between pairs of  wires ,two insulated cu wires are twisted. These are sometime enclosed in single cable this acts as a shield for twisted pair cable.

*For secure information this shield acts as ground and is called as shield twisted pair cable and for home transmit information this shield acts as unshielded and is called unshielded twisted pair cable.

*Major advantage is twisted pair is cheaper than coaxial cable and it overcomes EM induction.

*Disadvantage is slow transfer of information.

·         OPTICAL FIBER:

Up to this security is enough and every one needed the speed and thought of using the light as source to transmit the information as we knew that the speed of light is 3*108m/sec. Based on this technique optical fibre was designed. Similar to coaxial cable it also has 3 layers, outer one is buffer or sheath,middle one is cladding and the inner one where the light is gonna transmit is core. For proper transmission refractive index of core must be slightly greater than cladding. To know how light transmits in the core one should know about the critical angle and total internal reflection.

      *critical angle: When a wave is transmitting from one medium to another medium of different refractive indices and if wave incident angle is greater than 90 degrees this angle is referred as critical angle

      *Total internal reflection: When angle of incident is equal to critical angle then no reflection occurs only refraction into medium.

*By using these light parameters transmission is done in optical fiber. *Major advantages is Optical fiber carries much more information than normal cu wire and is not subjected to EM interference, so most telephone companies long distances lines are made of optical fibers by use of Repeaters at regular distances.
 2.     In case of wireless communication no wired media is present between transmitter and receiver. Here communication is by EM waves HOW? As I said before around a conductor both fields exists and these EM waves are necessary for communication.

The first wireless transmission went on air in early 20^th century using morse code. Later by modulation it made possible for transmitting voices and music via wireless.

Modes:

Wireless communication can be via,

·         Radio communication(Radio frequency)

·         Microwave communication(high frequency)

·         Infrared communication

·         Ultrasonic communication.are made of optical fibers by use of Repeaters at regular distances.

1.                                    

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Li-Fi(Light Fidelity) future wireless communication

In future it is suspected that every light bulb will be replaced by LED's the reason is LI-FI .Li-Fi  is acronym for light fidelity.The word fidelity means the ability of the receiver to reproduce all the signals.Light fidelity indicates transmission of data or information through light or illumination. The inventor defines it simply if LED is ON you transmit a digital '1' and if it is OFF you transmit a digital '0'.Li-Fi is the  next version to Wi-Fi(wireless fidelity) as it overcomes some of the limitations of Wi-Fi like speed,application areas like medical and in aircraft,outreach in remote areas etc.
NEED FOR LI-FI:
When you are using mobile phone or pc connected to wireless internet we have to compete for bandwidth and sometimes we get frustrated with slow speeds when more than one devices are connected. To solve this problem german scientist Herald Hass found an alternative way and he calls it with "data through illumination".He conveys that in future communication is done through Light in a room.
HOW IT GONNA WORK?
Li-Fi is transmission of data through illumination by taking fiber out of fiber optics by sending data through LED(light emitting diodes) light bulb that varies its intensity faster than human eye can follow.As said before  if LED is ON you transmit a digital '1' and if it is OFF you transmit a digital '0.As the reaction time of LED's to respond to the changes is very fast the transmission of data will also be fast. Theoretical calculations had proven that the rate of data transmission would be 224 giga bits per second.
*The requirements to adopt this technology are some LED's and controller that code data into those LED's
*Since it just uses light ,it can be used safely in aircraft and in hospitals that are prone to interference from radio waves.
*Simply radio waves are replaced by light waves in new method called Li-Fi.
*This method of using rapid waves of light to transmit information wirelessly is referred as Visible Light Communication(VLC) the transmitting frequency in VLC is around is 400Thz to 800Thz.
MAJOR APPLICATION AREAS OF LIFI:
1.IN FIELD OF MEDICAL:
Most hospitals donot allow Wi-Fi to enter into operating rooms due to radiation concerns and even it is lagged by some other cellphones or ipods, but communication is necessary in operation theaters  to treat patients.
LI-FI overcomes it.I think many of we know about the properties of light like inteference,diffraction ,polarization etc.Diffraction means bending up of light around the edges or obstacles.This property helps LI-FI to increase its efficiency.
2.AIRLINES: Where radio waves are not much efficient.
3.OUTREACH IN REMOTE AREAS:As the equipment for Wi-Fi is necessary, it is not possible to lay plant anywhere but since here in LI-FI it is through light we just need LED's and a controller.
4.UNDERSEAS:As it is difficult to lay optical fibers beneath water, it is better to communicate with help of light and as salt water is good conductor of electricity it is easy to work with LI-FI
5.FAST TRANSFER OF INFORMATION:As LED's ON and OFF very quickly which gives nice opportunities for fast transmitting the data.  

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