Features Of Electronics And Transistors

Introduction

The Electronics revolution, as this is known, accelerated the computer revolution and both these things have transformed many areas of our lives.

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Electronics is the study of how to control the flow of electrons. It deals with circuits made up of components that control the flow of electricity. Electronics is a part of physics and electrical engineering. Electrical components like transistors and relays can act as switches. This allows us to use electrical circuits to process information and convey information over long distances. Circuits may also take and amplify a weak signal.

The Electricity and Electronic Differences

Electricity:It's a sort of energy a very versatile kind of energy that we can make and use in many more ways. Electricity is all about making electromagnetic energy flow around acircuit so it will drive something like an electric motor or a heating element, powering appliances like electric cars, kettles, toasters, and lamps. Electrical appliances generally need a lot of energy. By contrast, electronic components use currents likely to be measured in fractions of milliamps (which are thousandths of amps). In other words, a typical electric appliance is likely to be using currents tens, hundreds, or thousands of times bigger than a typical electronic one.

Electronics is a much more subtle kind of electricity in which tiny electric currents (and, in theory, single electrons) are carefully directed around much more complex circuits to process signals (such as those that carry radio and television programs) or store and process information. Think of something like a microwave oven and it's easy to see the difference between ordinary electricity and electronics. In a microwave, electricity provides the power that generates high-energy waves that cook your food; electronics controls the electrical circuit that does the cooking.

The benefits of Electroics :

• Electronic equipment saves our lives in other ways too. Hospitals are filled with all sorts of electronic equipmentHospitals are packed with all kinds of electronic gadgets, from heart-rate monitors and ultrasound scanners to complex brain scanners and X-ray machines. Hearing aids were among the first gadgets to benefit from the development of tiny transistors in the mid-20th century, and ever-smaller integrated circuits have allowed hearing aids to become smaller and more powerful in the decades ever since.
• Entertainment was one of the first areas to benefit, with both radio (and later television) critically dependent on electronic components coming in. Although the telephone was invented prior to the proper development of electronics, modern telephone systems, cell phone networks and computer networks at the heart of the Internet all benefit from sophisticated digital electronics.

Basic Laws of Electricity

1. Ohm’s Law

The current through a conductor between two points is directly proportional to the voltage across the two points.

I = V / R or V = IR or R = V/I

2. Watt’s Law

Similar to Ohm's law, Watt's law states the relationship between power (watts), current and voltage.

P = VI or P = I2R

3. Kirchhoff's Current Law (KCL)

The total current or charge entering a junction or node is exactly equal to the charge leaving the node as it has no other place to go except to leave, as no charge is lost within the node. In other words, the algebraic sum of ALL the currents entering and leaving a node must be equal to zero.

Current In = Current Out

4. Kirchhoff's Voltage Law (KVL)

In any closed loop network, the total voltage around the loop is equal to the sum of all the voltage drops within the same loop, which is also equal to zero. In other words, the algebraic sum of all voltages within the loop must be equal to zero.

The Methods of Circuits Analysis

• Node Voltage Method : The Node Voltage Method is an organized methods of analyzing a circuit. The Node Voltage Method is based on Kirchhoff's Current Law. This technique is embedded inside the popular circuit simulator.

The Node Voltage Method breaks down circuit analysis into this sequence of steps:

1- Assign a reference node (ground).

2- Assign node voltage names to the remaining nodes.

3- Solve the easy nodes first, the ones with a voltage source connected to the reference node.

4- Write Kirchhoff's Current Law for each node. Do Ohm's Law in your head.

5- Solve the resulting system of equations for all node voltages.

6- Solve for any currents you want to know using Ohm's Law.

• Mesh Current Method : The Mesh Current Method is another well-organized method for solving a circuit. (The other is the Node Voltage Method.) As with any circuit analysis challenge, we have to solve a system of 2E, E independent equations, where E is the number of circuit elements. The Mesh Current Method efficiently manages the analysis task, resulting in a relatively small number of equations to solve. The Mesh Current Method is based on Kirchhoff's Voltage Law (KVL).
• Currrent Loop Method : is a small variation of the Mesh Current Method.

The changes are highlighted in this list of steps:

1. Identify the meshes, (the open windows of the circuit) and loops (other closed paths).
2. Assign a current variable to each mesh or loop, using a consistent direction (clockwise or counterclockwise).
3. Write Kirchhoff's Voltage Law equations around each mesh and loop.
4. Solve the resulting system of equations for all mesh and loop currents.
5. Solve for any element currents and voltages you want using Ohm's Law.

2. Content

Conductivity : is the phenomenon where something like heat , electricity or sound is transmitted. So, they (materials) may be categorized as conductors, semiconductors, or insulators based on the conductivity of each material and the existence of a forbidden distance.

The electrons of different types of atoms have different degrees of freedom to move around. With some types of materials, such as metals, the outermost electrons in the atoms are so loosely bound that they chaotically move in the space between the atoms of that material by nothing more than the influence of room-temperature heat energy. Because these virtually unbound electrons are free to leave their respective atoms and float around in the space between adjacent atoms, they are often called free electrons.

In other material forms, including glass, the electrons of the atoms have very little space to travel about. While some of these electrons may be forced by external forces such as physical rubbing to leave their respective atoms and transfer to the atoms of another material, they do not move very easily between atoms within that material.

This relative mobility of electrons within a material is known as electric conductivity. Conductivity is determined by the types of atoms in a material (the number of protons in each atom’s nucleus determines its chemical identity) and how the atoms are linked together with one another. Materials with high electron mobility (many free electrons) are called conductors, while materials with low electron mobility (few or no free electrons) are called insulators. Here are a few common examples of conductors and insulators.

Transistors

Our brain has about 100 billion cells called neurons the tiny switches that make you think about things and remember them. Computers also produce milliards of 'brain cells' in miniature. They 're called transistors and they're made from silicon, a widely found chemical element in sand.

A Transistor is a miniature electronic component that can do two different jobs. It can work either as an amplifier or a switch.

Transistor’s Operation

The transistors will act as switches. A tiny electrical current that flows through one part of a transistor may cause a much larger current to flow through another part. In other words the tiny current is transitioning to the bigger one. Essentially, this is how all the computer chips work. A memory chip, for example , contains hundreds of millions, or even billions of transistors, each of which can be individually switched on or off.

Since every transistor can be in two distinct states, two different numbers can be stored, zero and one. A chip can store billions of zeros and ones with billions of transistors, and almost as many ordinary numbers and letters (or characters as we call them). Less on that in a moment.

Transistor Manufacturing

The transistor is a three terminal device and consists of three distinct layers. Two of them are doped to give one type of semiconductor and the there is the opposite type, i.e. two may be n-type and one p-type, or two may be p-type and one may be n-type.. They are arranged so that the two similar layers of the transistor sandwich the layer of the opposite type. As a result these semiconductor devices are designated as either PNP transistors or NPN transistors according to the way they are made up.

Transistors can be designed to use very little power. Millions of them in a watch or calculator can run for years on a small battery.

1. Base: The transistor base gets its name from the fact that this electrode formed the basis for the entire system in early transistors. The earliest point contact transistors mounted two dot contacts on the base material. This basic material formed the foundation connection.
2. Emitter: The emitter gains its name from the fact that it emits the charge carriers.
3. Collector: The collector gains his name from collecting the carriers of charges.

A transistor can be considered as two P-N junctions placed back to back. One of these, namely the base emitter junction is forward biased, whilst the other, the base collector junction is reverse biased. It is found that when a current is made to flow in the base emitter junction a larger current flows in the collector circuit even though the base collector junction is reverse biased.

For clarity the example of an NPN transistor is taken. The same reasoning can be used for a PNP device, except that holes are the majority carriers instead of electrons.

When current flows through the base emitter junction, electrons leave the emitter and flow into the base. However the doping in this region is kept low and there are comparatively few holes available for recombination. As a result most of the electrons are able to flow right through the base region and on into the collector region, attracted by the positive potential.

PNP Transistor and NPN Transistor

NPN and PNP transistors are bipolar junction transistors, and it is a basic electrical and electronic component which is used to build many electrical and electronic projects. The operation of these transistors involves both electrons and holes. The PNP and NPN transistors allow current amplification. These transistors are used as switches, amplifiers or oscillators. Bipolar junction transistors can be found either as large numbers as parts of integrated circuits or in discrete components. In PNP transistors, majority charge carriers are holes, whereas in NPN transistors, electrons are the majority charge carriers. But, field effect transistors have only one type of charge carrier.

The formation of these transistors is based on the diodes with the junction p-n. As in the n-p-n transistors n-types are in majority therefore there includes excess amount of electrons as the charge carriers. In p-n-p transistors there are two p-types in it resulting in the majority charge carriers as holes.

The main difference between the NPN and PNP transistor is, an NPN transistor turns on when the current flows through the base of the transistor. In this type of transistor, the current flows from the collector (C) to the emitter (E). A PNP transistor turns ON, when there is no current at the base of the transistor. In this transistor, the current flows from the emitter (E) to the collector (C).Thus, knowing this, a PNP transistor turns ON by a low signal (ground), where NPN transistor turns ON by a high signal (current).

PNP Type

The PNP transistor is a bipolar junction transistor; In a PNP transistor, the first letter P indicates the polarity of the voltage required for the emitter; the second letter N indicates the polarity of the base. The working of PNP transistor is the exact opposite to the NPN transistor. In this type of transistor, the majority charge carriers are holes. Basically, this transistor works the same as the NPN transistor. The materials which are used to construct the emitter, base and collector terminals in the PNP transistor are different from those used in the NPN transistor. The PNP transistor bias setup is shown in the below figure. The base-collector terminals of the PNP transistor are always reversed biased, then the negative voltage must be used for the collector. Therefore, the base terminal of the PNP transistor must be negative with respect to the emitter terminal, and the collector must be negative than the base.

The PNP transistor are formed with n-type present in between the p-types. The majority of the carriers those are responsible for the generation of the current are in this transistor are holes. The working operation is similar to that of n-p-n. But the applications of the voltages or currents in terms of polarity are different.

NPN Type

The NPN transistor is a bipolar junction transistor, In an NPN transistor, the first letter N indicates a negatively charged layer of material and a P indicates a positively charged layer. These transistors have a positive layer, which is located in-between two negative layers. NPN transistors are generally used in circuits for switching, amplifying the electrical signals that pass through them. These transistors comprise three terminals namely, base, collector and emitter and these terminals connect the transistor to the circuit board. When the current flows through the NPN transistor, the transistor base terminal receives the electrical signal, the collector makes a stronger electric current than the one passing through the base, and the emitter passes this stronger current on to the rest of the circuit. In this transistor, the current flows through the collector terminal to the emitter.

Semiconductor Role in the Electronic Revolution

Without transistors and integrated semiconductor circuits most of modern life will be very different. No handheld electronic games would keep children entertained for hours. No barcode readers will speed up checkout lines, and at the same time compile inventories. And no computers would manage job and home duties, nor would microprocessors power car operations.

The semiconductor industry has changed in only the last 50 years from an emerging technology to one that itself enables new technologies. And the main benefactor of this metamorphosis as well as the current drivers for semiconductors are the information technologies, which are responsible for the increasing ability to digitize information and disperse that content. The creation of the Internet enabled a new set of structures and the idea of a self-developing and ownerless information system. The next step for information technologies will be the mobile revolution, where information becomes pervasive and, at the same time, personal. The ubiquitous nature of information and its access humanizes the information.

Transistors, and many other electronic devices, are made of semiconductors — materials that conduct electricity only weakly under certain conditions. Radar technology, developed during World War II, used tow semiconductors, germanium and silicon, to detect short-wave radio signals. Although the theory on which the Bell Labs scientists based their work was largely the product of the 1920s and 1930s, the wartime experience of purifying these elements and explore.

3. Conclusion

Much of the progress in the past 60 years has been because of the success of the transistor. Invented in the 1940s, it replaced vacuum tubes in televisions, radios and other electronic equipment. Its ruggedness, small size and low power consumption produced a wave of miniaturization resulting in home computers, digital cameras, cell phones and other devices. Research in transistors is ongoing; the capability of electronics will continue to improve for the foreseeable future.

The Advantages of Transistors

• Smaller mechanical sensitivity.
• Lower cost and smaller in size, especially in small-signal circuits.
• Low operating voltages for greater safety, lower costs, and tighter clearances.
• Extremely long life.
• No power consumption by a cathode heater.
• Fast switching.

The Disadvantages of Transistors

• Due to its small size, it is difficult to trace out faulty ones due to failure. Moreover it is very difficult to unsolder and replace new ones.
• Manufacturing techniques are very complex and requires clean room environment.
• Transistor has non zero ON resistance. Hence when it is ON, voltage across transistor is never zero. Moreover during OFF state also, there is flow of small leakage current. Hence it does not work as efficiently as mechanical switch or electrical switch or relay.