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This purpose of this report is to provide a reliable and accurate summary of the way transistor technology operates, and to cover (in depth) the uses and impacts of transistor technology on society. This paper also briefly covers the history of transistors, recent developments in transistor technology and provides some insight into related technologies (including integrated circuits, display screens and amplifying circuits).
b. Brief overview of report
Transistor technology is invaluable in modern society. Without the invention of the transistor, the 'information age' would not have occurred. Transistors date back to the mid 20th century, and transistor technology has improved vastly since the creation of the first transistor in 1947. Many scientists contributed to the development of the transistor, which was to replace the existing outdated valve technology. But are transistors the final development in computing and amplification technology?
Transistors are integral to modern society. Much technology so often taken for granted would be non-existent were it not for the invention of the transistor. But the transistor was not invented overnight. Many, many years of hard work and effort were needed to produce the transistors that we see and use today.
a. Brief history of the transistor
The invention of the transistor stemmed from the development of vacuum tubes , which were used in the first diodes and triodes. Experimentation with semiconductor materials quickly led to the invention of the solid-state diode, invented by the German physicist Karl Ferdinand Braun in 1898 . In 1908, after the invention of the triode by Lee De Forest , the invention of the transistor seemed imminent. However, despite this, it was 17 years until the first patent for the field-effect transistor principle was filed by Julius Edgar Lilienfeld in 1925 , and then another 22 years until John Bardeen, Walter Brattain and William Shockley of Bell Labs demonstrated the first working transistor (1947) . Following this, many companies began to apply the technology to consumer devices, primarily radios, and the era of low-cost mass-market, portable consumer electronics had begun .
b. The need for transistors in society
Transistors are used in all of the electronic devices we rely on today . Without the invention of transistors the world would be vastly different; many facets of society would not have evolved since the late 19th century. The 'information age' would never have taken place .
Business: Since the popularisation of personal computers for business use by IBM (with the IBM Personal Computer XT) and Apple (with the Apple Macintosh) in 1983, businesses around the world have relied on computers for literally everything , . Vast improvements in productivity have resulted. Without the invention of the transistor, computers would not exist and businesses would most likely still be relying on paper-based information systems, which are notoriously slow, inefficient, unadaptable, bulky and tedious to use.
Communication and Entertainment: Radio and television technology, now vastly popular, relies wholly on amplification of signals using transistors. Without amplification, reception of transmitted signals over any distance longer than a few metres is practically impossible. The invention of the transistor now allows mobile phone users to transmit and receive voice signals up to 35 km away with devices that fit easily in their pockets . Also, modern televisions (now very thin, portable, reliable and energy efficient) are a direct result of the invention of the transistor, as they use transistors to amplify received video signals . Additionally, transistors are used for music amplification (e.g. guitar amplifiers) .
III. Research Topic
Transistors, although very useful, are utterly complex and come in many different variations. It therefore comes as no surprise that it took many years to develop the first transistor, even after the successful creation of triodes and solid-state diodes. However, the successful production of the first working transistor by Bell Laboratories in 1947  led the way to a whole new chapter in the history of mankind.
e. How transistors work (and transistor variations)
How transistors work: Transistors utilise semiconductor technology for the amplification and switching of electronic signals . Semiconductors are unlike conductors and insulators, in that when a lattice of semiconductor material is heated, it's conductivity increases, where a conductor's conductivity would decrease (due to obstruction of the electrons` paths by "vibration" of atoms in the material), and an insulator's conductivity would remain unchanged (until reaching the breakdown voltage). This can be seen in the following band diagrams:
When the semiconductor lattice is heated, electrons move up from the valence band into the conduction band, thus increasing the lattices conductivity . However, this "jump" still requires quite some energy, much more than is ideal for use in fine electronics circuits. As such, the semi-conductor materials (mostly group 4 elements) are doped with either group 3 dopants (such as boron or gallium) or group 5 dopants (such as phosphorous or arsenic) to form p-type materials (deficiency of electrons) and n-type materials (abundance of electrons) respectively . P-type materials have what is called an acceptor level, which accepts electrons from the conduction band, and n-type materials have what is called a donor level, where electrons are donated to the conduction band . The unique properties of such semiconductor material are what give diodes and transistors such a diverse range of uses, as can be seen in society today .
By taking advantage of the chemical properties of the doped semiconductors (normally doped Silicon) , transistors are used to accomplish a feat that would have been otherwise impossible. In order to explain in as much detail as possible how the transistor works, we will first look at a simple bipolar PNP transistor in a simple amplifying circuit:
"For a PNP transistor, mobile electrons in the n-region initially move away from the junctions towards the positive terminal. The holes in each of the p-regions also move away from the junctions towards the negative terminals. When the emitter is slightly positive, or forward biased, holes move across the junction into the n-region, or base. Most of the holes do not recombine with electrons in the base but flow across the second junction into the collector."  Hence, a small input current applied emitter-to-base can be used to control the emitter-to-collector internal resistance, making this device able to be used as an amplifier or switch , .
Types of Transistors: There are two key types of transistors :
Bipolar transistors consist of a layer of p- or n-type material sandwiched between two layers of n- or p-type material respectively, and base, collector and transmitter terminals.
Like the NPN, a small input current signal applied emitter-to-base in the transistor is used to control the emitter-to-collector internal resistance. Often used in amplifiers and switches for a wide variety of purposes. The only difference between NPN and PNP transistors is that the power supply polarities are different. 
Field Effect Transistor (FET)
Junction Field Effect Transistor (JFET)
JFETs are a type of field effect transistor that consists of a channel of n- or p-type material with two p- or n-type terminals (respectively) that surround it. When a voltage is applied to the gate terminal, an electric field is formed which impedes the flow of charge in the channel. 
nAn input voltage signal applied to the gate-source junction is used to control the source-to-drain internal resistance. Often used for amplifier circuitry. 
Like JFETs, MOSFETs come in n- and p-channel varieties.
MOSFETs also come in both single gate and dual gate variations, however the most commonly used type is the single gate MOSFET; the dual gate MOSFET is only used for specialised radio frequency applications . MOSFETs are "similar to JFETs except the input voltage is capacitive coupled to the transistor" . Because MOSFETs are inexpensive, easily fabricated and draw little power, they are now the most commonly used type of transistor in integrated circuits (ICs) . They are however, easily damaged by static discharge .
e. Invention of semiconductor devices: the first transistor
At the dawn of the 20th century, the need for a replacement for thermionic devices was clear. They had many disadvantages:
the cathode would require heating (in order to liberate electrons) 
they would require a high voltage current (to overcome the resistance of gas molecules still left in the tube) 
they were bulky (contained many different components) 
they were fragile (made of glass) 
they did not last long, and were hence unreliable (due to heat, cathode poisoning, internal short-circuits and loss of vacuum) ; and
they required a lot of power 
Fig. 16 - Typical Thermionic ValveMany research teams set to work to try and find the solution:
1880, February 13: While trying to perfect his light bulb design, Edison notices that the filaments on his light bulb always seemed to burn out at the positive-connected end. He constructs a special light bulb that has a metal plate sealed inside it, accidentally fabricating the first thermionic diode. After experimentation, he is unable to find any practical use for the device, so he writes off the discovery as unimportant , .
1899: Following much hard work, Karl Ferdinand Braun patents the crystal rectifier, later to be called the solid-state diode .
1900 (approx.): John Ambrose Fleming discovers a use for Edison's light bulb modification as a precision radio detector .
1904, November 16: Fleming patents the first thermionic diode .
1906: Lee De Forest develops the first triode, which he calls the 'Audion' , .
1925: Julius Edgar Lilienfeld files the first patent for a transistor, but never publishes a paper or constructs any such device .
1934: German inventor, Oskar Heil patents a device similar to Lilienfeld's .
Fig. 17 - Replica of the Bell Labs transistor1947: Walter Brattain and John Bardeen of Bell Labs discover that when electrical contacts are applied to a crystal of Germanium, the output power is larger than the input. Group leader William Shockley sees potential in such a discovery, and builds an operational transistor (of Germanium) based on Lilienfeld's designs. He is named the "father of the transistor" , .
1954: Gordon Teal of Texas Instruments (and formerly Bell Labs) develops the first silicon transistor, as he has the knowledge of how to grow silicon crystals to a high purity. Previously, only Germanium crystals could be grown to a high enough purity .
1950's and onwards: Transistors quickly replace valve technology, and many companies begin developing portable electronic devices. Many companies began to apply the technology to consumer devices, primarily radios, and the era of low-cost mass-market, portable consumer electronics had begun .
Fig. 18 - 1958 Sony Portable RadioToday: Transistors now form the basis of our society, and are contained in every electronic device we use .
f. Why are transistors so useful?
Transistors are practically everywhere. They govern all the spheres of modern life. Transistors are widely adaptable to a vast range of situations and applications . They are used in computers, stereos and televisions, mobile phones, in calculators, in cars, in watches: practically every electric device will use a transistor for one purpose or another . The reasons they are so vastly used include:
Compactness (very simple with only 6-10 separate components) 
Reliability (solid-state, don't require heating or undergo cathode poisoning like thermionic valves) 
Adaptability (can be used for any number of application, the most obvious being switching and amplification) 
Low power consumption (does not require a heating circuit, or high voltage power source) ; and
Durability (aren't fragile because they are solid-state, although MOSFETs are sensitive to static discharge) 
Fig. 19 - Typical MOSFETModern society and the 'information age' rely wholly on transistors: without them society would be nothing like what we see today .
g. A world without transistors: where would society be?
In order to truly understand the importance of transistors in modern society, and see the impact it has made upon our lives, one must consider the alternative: what if transistors were never invented?
Without transistors, long distance radio and wired communication would not be easily possible. Paper mail would most likely still be the dominant form of communication, with the use of valve-based radios restricted to those who could afford it . Modern computers would not exist; computers would operate using valves, and hence would be slow, bulky and unreliable. Portable computing would be a pipedream . Mobile electronic devices such as music players or mobile phones would not have been invented or, if so, would not be by any means portable . The enormous network of freely available information that is now called the internet would most likely be very small, or only exist for military use. Libraries would most likely still be the primary source of information .
Without the transistor, any technological advancements would be made very difficult or expensive, and society would most likely not have changed much since the 1950's .
The transistor is indispensible in modern society. The advancements in transistor technology since the turn of the 20th century are amazing. Tedious, unreliable thermionic valves have been replaced with a much superior alternative.
But are transistors the final frontier? To find out, we must boldly go where no physicist has gone before.