Nano-technology and Nano-science

The latest and sensitive topic of new generation is nano-technology. Nano technology is the science ,engineering and technology conduct at nano scale i.e about 1 to 100 nano scale. Nanotechnology and nano science are the study and application of extremely small things and can be used across the field of science like biology, chemistry, physics, math, engineering, and material science. It is hard to imagine that how small nano technology is. One nano meter is just equal to 10^-9 of a meter.  The father of nanotechnology was Physicist Richard Feynman .

It is one of the interesting topic of science and technology. It is involve in the ability to see and prevent individual atoms and molecule, Earth where we are surviving our life is made up of these small atoms for eg;- the food we eat, the clothes we wear, the building and house we live and our bodies too. We are not able to see some of small atom with our naked eyes. And also impossible to see with the microscope which we used in our high school science class. The microscope need to see nano scales thing were invented 30 years ago.

Application of nano technology .

Nano technology can be use in every sector related with science and technology as shown in the given figure.

a)Medical science 

Nanotechnology is used to treatment of disease.Nano-medical ranges from the medical application of nano-material and biological devices like biosensor and even future application of molecular nanotechnology such as biological machines. Nano material can be useful for both vivo and vitro biomedical research and its application. And it lead to the development of diagnostic devices, contrast agents, analytical tools, physical therapy application and drugs delivery vehicles.

b)Nano biotechnology 

Nano biotechnology, biotechnology, nano biology are the terms derived from the intersection of nanotechnology and biology. Its help us to biological research with various field of nanotechnology. Nano devices such as biological machines, nano particals, and nano scale are the biological term of nanotechnology.

c)Industrial 

 Nano technology is also used in industrial sector to easier their work. Its is used to easy to clean to scratch  resistant for example car bumper are made lighter, clothing is more stain repellent, sunscreen is more radiation resistant, cell phone screen are lighter weight and many more. Using of nano tech change all the electronic appliance of industries make smart through embedded wearable electronics.

How gate work

Logic gate

 The digital circuit which follows the logical relation between input and output voltages. Its system is depend in only two numerical input i.e. 0 or 1 here 0 refer to low and 1 refer to high. In this gate there is only one output for one or more than one input. There are different type of logic gate they are 

1) OR gate 

2) AND gate

3) NOR gate

4) NAND gate

1) OR gate
It is the logic gate which provide the high output if one of the input is high. It has two or more than two input and only one output. It can express as Z=X+Y.

Explanation of OR gate

The circuit diagram of OR gate using two diode D1 and D2 as shown in figure. A and B are input and Y is output. Here  0 potential mean 0 state and positive mean 1 state. The operation of OR gate is explained as follows:

• When A is 0 volt and B is also 0 volt then the diode D1 and  D2 don't conduct current hence there is no flow of current through the diode as well as load resistance Rl. So output is low i.e   Z=X+Y=0+0=0.
• When A is 0 volt and B is +5V volt then the diode D1  don't conduct D2 conduct current hence there is flow of current through the diode D2 as well as load resistance Rl. So output is high i.e Z=X+Y=0+1=1.
•  When A is +5V volt and B is 0 volt then the diode D1 conduct current but D2 don't conduct current hence there is flow of current through the diode D1 as well as load resistance Rl. So output is high i.e Z=X+Y=1+0=1.

• When A is +5V volt and B is +5V volt then the both diode conduct current hence there is flow of current through the diode as well as load resistance Rl. So output is high i.e Z=X+Y=1+1=1.

2) AND gate

 It is the logic gate which provide the high output if both the input is high. It has two or more than two input and only one output. It can express as Z=A.B

Explanation of AND gate

The circuit diagram of AND gate using two diode D1 and D2 as shown in figure. A and B are input and Y is output. Here  0 potential mean 0 state and positive mean 1 state. The operation of OR gate is explained as follows:

• When A is 0 volt and B is also 0 volt then the diode D1 and  D2 don't conduct current hence there is no flow of current through the diode as well as load resistance Rl. So output is low i.e   Z=X+Y=0+0=0.
• When A is 0 volt and B is +5V volt then the diode D1  don't conduct D2 conduct current hence there is flow of current through the diode D2 as well as load resistance Rl. So output is high i.e Z=X+Y=0+1=1.
•  When A is +5V volt and B is 0 volt then the diode D1 conduct current but D2 don't conduct current hence there is flow of current through the diode D1 as well as load resistance Rl. So output is high i.e Z=X+Y=1+0=1.

• When A is +5V volt and B is +5V volt then the both diode conduct current hence there is flow of current through the diode as well as load resistance Rl. So output is high i.e Z=X+Y=1+1=1.

3) NOR gate

 It is the logic gate which provide the high output if  both the input is low. It has two or more than two input and only one output. And the logic gate provide low output if both then input is high. Its work as shown in the given truth table. Its can be express as X = A+B.

Explanation of NOR gate

The circuit diagram of NOR using two diode D1 and D2 as shown in figure.A  and B are input and X is output. Here  0 potential mean 0 state and positive mean 1 state. The operation of NOR gate is explained as follows:

• When A is 0 volt and B is also 0 volt then the diode D1 and  D2 conduct current hence there is flow of current through the diode as well as load resistance Rl. So output is low i.e   X = A+B=0+0=1.
• When A is 0 volt and B is +5V volt then the diode D1 and D2 don't conduct current hence there is no flow of current through the diode as well as load resistance Rl. So output is low i.e X = A+B=0+1=0.
•  When A is +5V volt and B is 0 volt then the diode D1 and D2 don't conduct current hence there is no flow of current through the diode as well as load resistance Rl. So output is low i.e X = A+B=1+0=0.

• When A is +5V volt and B is +5V volt then the diode D1 and D2 don't conduct current hence there is no flow of current through the diode as well as load resistance Rl. So output is low i.e X = A+B=1+1=0.

4) NAND gate

 It is the logic gate which provide the low output if  both the input is high and if one of the the input is low then its output is high. Its can be express as AB=A+B.

INPUT		OUTPUT
A	B	A NAND B
0	0	1
0	1	1
1	0	1
1	1	0

Explanation of NAND gate

 The circuit diagram of NAND gate using two diode D1 and D2.A  and B are input and Q is output. Here  0 potential mean 0 state and positive mean 1 state. The operation of NAND gate is explained as follows:

• When A is 0 volt and B is also 0 volt then the diode D1 and  D2 conduct current hence there is flow of current through the diode as well as load resistance Rl. So output is low i.e   AB=A+B=0+0=1.
• When A is 0 volt and B is +5V volt then the diode D1 and D2 conduct current hence there is flow of current through the diode as well as load resistance Rl. So output is high i.e AB=A+B=0+1=1.
•  When A is +5V volt and B is 0 volt then the diode D1 and D2 conduct current hence there is flow of current through the diode as well as load resistance Rl. So output is high i.e AB=A+B=1+0=1.
• When A is +5V volt and B is +5V volt then the diode D1 and D2 don't conduct current hence there is no flow of current through the diode as well as load resistance Rl. So output is low i.e AB=A+B=1+1=0.

How the transistor help in our daily life.

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Transistors believe semiconductors to figure their magic. A semiconductor may be a material that’s more or less a pure conductor (like copper wire) however additionally not associate material (like air). The physical phenomenon of a semiconductor – however simply it permits electrons to flow – depends on variables like temperature or the presence of a lot of or less electrons. Let’s look shortly beneath the hood of a junction transistor. Don’t worry, we have a tendency to won’t dig too deeply into physical science.

A junction transistor as two Diodes

Transistors are reasonably like associate extension of another semiconductor component: diodes. in an exceedingly method transistors are simply 2 diodes with their cathodes (or anodes) tied together:

Transistors as 2 diodes

The diode connecting base to electrode is that the necessary one here; it matches the direction of the arrow on the schematic image, and shows you which of them method current is meant to flow through the junction transistor.

The diode illustration may be a sensible place to begin, however it’s removed from correct. Don’t base your understanding of a transistor’s operation thereon model (and positively don’t attempt to replicate it on a bread board, it won’t work). There’s an entire heap of weird physical science level stuff dominant the interactions between the 3 terminals.

(This model is helpful if you wish to check a junction transistor. exploitation the diode (or resistance) take a look at perform on a multimeter, you'll be able to live across the BE and before Christ terminals to visualize for the presence of these “diodes”.)

Transistor Structure and Operation

Transistors ar designed by stacking 3 completely different layers of semiconductor material along. a number of those layers have additional electrons additional to them (a method known as “doping”), et al. have electrons removed (doped with “holes” – the absence of electrons). A semiconductor material with additional electrons is termed associate n-type (n for negative as a result of electrons have a negative charge) and a cloth with electrons removed is termed a p-type (for positive). Transistors ar created by either stacking associate n on prime of a p on prime of associate n, or p over n over p.

Simplified NPN construction

With some hand waving, will|we will|we are able to} say electrons can simply ensue n regions to p regions, as long as they need a trifle force (voltage) to push them. however flowing from a p region to associate n region is admittedly exhausting (requires plenty of voltage). however the special issue a few junction transistor – the half that creates our two-diode model obsolete – is that the undeniable fact that electrons will simply ensue the p-type base to the n-type collector as long because the base-emitter junction is forward biased (meaning the bottom is at a better voltage than the emitter).

Active junction transistor current flow

The NPN junction transistor is meant to pass electrons from the electrode to the collector (so typical current flows from collector to emitter). The electrode “emits” electrons into the bottom, that controls the quantity of electrons the electrode emits. Most of the electrons emitted ar “collected” by the collector, that sends them on to consequent a part of the circuit.

A PNP works in an exceedingly same however opposite fashion. the bottom still controls current flow, however that current flows within the wrong way – from electrode to collector. rather than electrons, the electrode emits “holes” (a abstract absence of electrons) that ar collected by the collector.


The junction transistor is reasonably like associate negatron valve. the bottom pin is sort of a handle you would possibly suits enable a lot of or less electrons to ensue electrode to collector. Let’s investigate this analogy further…

Transistor

Transistor is the crystal which three doped crystal like N P and N.

There are mainly three terminal they are

a)Emitter(E)

It is heavily doped part of the transistor.Its main task is to carry majority charge carrier. It denoted by symbol E.

b)Base(B)

Middle part of transistor called base.It is very thin part of its.As compare to other region it is 10^-6m thin. Its main task is to pass the majority charged carrier from emitter to collector.It is very lightly doped to minimized the reunion of free electron and holes. Its denoted by the symbol B.

c)Collector(C)

It is the last or third region of the transistor. It is moderately doped region. Its task is to collect the majority charge carrier endow by emitter and pass through base. Mainly this region is physically larger than other region because to evaporate the greater heat generated in the collector.

There are two type of transistor they are:-

1)N-P-N Transistor
It is the transistor formed by growing a thin layer of p type crystal between two layer of N type crystal. In the NPN Transistor free electron are the majority charge carrier in the emitter and collector in other hand holes are the majority charge carrier in the base.

Working process of N-P-N Transistor

The circuit diagram of NPN transistor is shown in figure. Here battery VBE acts as forward bias and reverse bias by battery VCB to the transistor. When collector base junction is forward bias then VBE>0.7V for silicon and 0.3V for germanium. Then hole act majority charge carrier in N type flow from emitter  toward the P type base resulting the flow of current through the emitter known as emitter current Ie. The base is thin and likely doped as compared to emitter and collector. Thud 5%of the hole recombined with the electron in the base region resulting the flow of current through the base known as base current Ib.The majority of hole 95% enter into the collector region. The flow of this electron in the collector region called collector current Ic. The electron in the collector region attract toward the positive terminal of the battery VCB and recombined at the same time and equal number of electron entre the emitter regions from the negative terminal of the battery VBE.

2)P-N-P Transistor

It is the exactly opposite to the NPN transistor. We have already learn the function or working process of  NPN transistor. It is the transistor formed by growing of thin layer of N type crystal between two P type of crystal.In the PNP Transistor free electron are the majority charge carrier in the base in other hand holes are the majority charge carrier in the collector and emitter.

Working process of P-N-P Transistor

We have already said that it is exactly opposite to the NPN transistor,The circuit diagram or figure also clearly show that. The circuit diagram of PNP transistor is shown in figure. Here battery VBE acts as reverse bias and forward  bias by battery VCB to the transistor. When collector base junction is reverse bias then VBE>0.7V for silicon and 0.3V for germanium. Then hole act majority charge carrier in P type flow from emitter  toward the N type base resulting the flow of current through the collector known as collector current Ic. The base is thin and likely doped as compared to emitter and collector. Thud 5%of the hole recombined with the electron in the base region resulting the flow of current through the base known as base current Ib.The majority of hole 95% enter into the emitter region. The flow of this electron in the emitter region called emitter current Ie. The electron in the emitter region attract toward the positive terminal of the battery VCB and recombined at the same time and equal number of electron entre the collector regions from the negative terminal of the battery VBE.

Rectifier

An electrical circuit which converts the AC current into DC current.Such process is known as rectification.There are two type of rectifier i.e

1)Half wave rectifier

2)Full wave rectifier

1)Half wave rectifier

Rectifier which rectified only half of its AC current to DC. Output is obtain only during alternating half cycle of input AC current.

Working process of half wave rectifier

Its working is based on the fact that the resistance of p-n junction become low when forward bias and become high when reverse bias.

The circuit diagram of half wave rectifier is shown in figure. Its consist of a Transformer a p-n junction diode 'D' and the load resistance 'RL'. The primary coil of the transformer is connected to the AC mains and the secondary coil is connected to the load resistance RL through the diode D. The DC output is drawn from the load resistance RL. During the positive half cycle of secondary voltage the diode D is forward bias therefore the current flow through the diode and the load resistance hence diode conduct easily.Similarly during half cycle of secondary voltage the diode act as reverse bias therefore there is no conduct of current through diode and load resistance. In this way half wave rectifier works.

2)Full wave rectifier

The rectifier which rectified full of its AC current to DC voltage.Output is obtained during both half cycle of its AC supply input. There is two type of full wave rectifier.

a)Center tapped full wave rectifier

Rectifier which rectified full of AC input to DC output by using two diode connected to the center tapped secondary coil of the transformer and load resistance 'RL'.

fig:a

fig:b

Working process of center tapped full wave rectifier

We have already discuss about full wave rectifier. It is based on the fact that the resistance of P-N junction becomes low when forward bias and become high resistance when reverse bias.

The circuit diagram of a full wave rectifier is shown in figure. The diode (D1 and D2) are connected to the center tapped secondary coil of the transformer and the load resistance (R) in such a way that the diode conduct during alternate cycle of the input AC supplied.

During positive half cycle of secondary voltage upper diode D1 is forward bias and lower diode D2 is reverse bias. Thus the current flows through diode D1 and load resistor R. During negative half cycle of secondary voltage upper diode D1 is reverse bias and lower diode D2 is forward bias. Thus the current flows through diode D2 and load resistor R.Here the half wave of input AC supplied Vin is rectified by one diode D1 and the next half wave is rectified by diode D2. Fig(b) show the rectified output voltage Vout obtain across the load resistor R for the supplied input AC voltage. The current flows through R are the same direction for both half cycle. Thus the output current through the load is said to be direct current.

b)Bridge rectifier

Rectifier which rectified full of AC input to DC output by using four diode connected to form a bridge.

Working process of bridge rectifier

Its working is based on the fact that the resistance of p-n junction become low when forward bias and become high when reverse bias.

The circuit  diagram of bridge rectifier  is shown in figure it consist of four diode D1,D2,D3 and D4 connected to form bridge. the input of acis applied across the primary coil  of the transformer the end of the secondary coil are connected to the two opposite end and the b and d are connected to the load resistance .The voltage drop across the load resistance give the output voltage.

When an AC input is applied to the primary coil of the transformer the voltage induced in the secondary coil .During positive half cycle of the secondary voltage suppose one end X of the secondary coil 'S', is positive and its other end Y is at negative. Then the diode D4 and D2 is forward bias and D1 and D3 are reverse bias. D2 and D4 conduct current through the load resistance and D1 and D doesn't conduct current.Again during the negative half cycle of secondary voltage suppose one end is Y at positive then the diode D2 and  D4 act as reverse bias so it doesn't conduct current but diode D1 and D3 act forward bias so they conduct current through the load resistance .In both cycle the current through cycle the AC input supplied is rectified full input dc. This way bridge rectifier work.

Diode

fig; symbol of diode

A diode is a  electronic component having two terminal and of low resistance that conducts current in single direction.But it have opposite nature to opposite direction i.e high  resistance in the another direction. A semiconductor diode, the most common type diode which are mostly used in our daily life equipment.It is a crystalline piece of semiconductor material with a p–n junction connected to two electrical terminals.

Diode are mostly made up of silicon and germanium.

There are many type of diode some common diode which are used in our daily life are 

1)PN junction diode

2)Zener diode

3)Tunnel diode

4)Schottky diode

5)Varacfor diode

1)PN junction diode

When p type of semiconductor is join with a n type of semiconductor so as to form one piece ther assemble so obtain known as p-n junction diode or simply junction diode. Holes are the majority charge carrier and electron are the minority charge carrier in p type of crystal and simirally in n-type of crystal the electron are majority charge carrier and holees are minority charge carrier.

 2)Zener diode

It is a reverse bias strongly doped silicon or germanium p-n junction diode which is used in the breakdown rregion where current is limited by for external resistance and dispassion of diode. Its is mainly used in breakdown region in reverse bias condition so that its also known as breakdown diode.

Semiconductor and Its Type

Semiconductor is the type of conductor whose conductivity lies between conductor and insulator. On other hand the material having four valance electron is known as semi-conductor. For example :- Gernium and silicon are the example of semiconductor.  The outermost electron or valance electron are four  in both material. There are two type of semiconductor i.e

1)Pure semiconductor

2) Impure semiconductor

1)Pure semiconductor

The Silicon Z=14 is a pure semiconductor. the silicon atom consists of four valance electron surrounding the nucleus and tightly bounded electron. It's central silicon atoms shares it's four valance electron with four adjacent atoms to form covalent bond. In this way the central atom have total eight electrons.

2) Impure semiconductor

When the pure semiconductor is dopped with suitable impurities we obtain a crystal known as impure semiconductor or externsic semiconductor. These are of two type

a)n-type semiconductor

b)p-type semiconductor

a)n-type semiconductor

 The material which have excess of free electron is known as n-type semiconductor. n stands for negatively charged electrons. When the pure silicon crystal is doped with pentravalent electron i.e Arsenic, Phosphorous and Atomuni then four out of five electron in its outermost orbit form the covalent bond with four electron of outermost orbit of silicon atom. The rest of one electron is free in the crystal has shown in figure.

b)p-type semiconductor

The crystal which have excess of hole is known as p-type semiconductor. Here p stands for positive charge. When the silicon is doped with trivalent i.e Aluminium, Boron then only three  electron out of four in outermost electron forms the covalent bond with three electrons in the outermost cell of aluminium. Atom there by leaving one valancy of hole in new electronic configuration such type of crystal is known as p-type semiconductor. In this case the electronic current due to hole such behaves as positive charge. This type of semiconductor is shown in figure.