Several historians of technology consider the transistor as "the greatest invention of the twentieth century." It is the basic electronic device that led to the circuits integrated and other elements of the high level of integration.
Just as the nineteenth century industrial revolution was established based on the steam engine of James Watt, one can say that the era of communications has been established based on the transistor.
The exact date was December 16, 1947, when William Shockley, John Bardeen and Walter Brattain put together the first transistor. Soon after, a computer composed of these transistors weighed about 28 tons and consumed about 170 MW of energy.
Later Bell Labs transistor tubes became such electrical switches, triggering a series of bids and rivalries between those involved in the issue. But the truth is that, thanks to this important invention, now you can read this information on a computer screen.
Photograph of the first transistor built by W. Shockley, J. Bardeen and W. Brattain in December 1947 (Photo: bellsystemmemorial.com)
however, had drawbacks they become impractical some of the applications then revolutionize our knowledge society. One of its major drawbacks was that it used a lot of energy to function. This was caused because the valves electrically heated filament (cathode) to emit electrons which are then collected on an electrode (anode), thereby establishing an electrical current. Then, through a small voltage (shortstop), applied between grid and cathode, the amplifying effect is achieved by controlling the current value of greater intensity, between the cathode and anode.
transistors, developed in 1947 by physicists Shockley, Bardeen and Brattain, solved all these problems and lead the way, even that, along with other inventions, such as integrated circuits, would enhance the development of computers. And all at low voltages, without need to dissipate energy (as was the case of the filament) in small size and no moving parts that could break or incandescent.
filament not only consumed a lot of energy, but also used to burn, or vibration managed to break it so the valves end up being unreliable.
Moreover, as was necessary to prevent oxidation of the filament, the valve was made by a glass case, containing an inert gas or vacuum, making the whole is much more voluminous.
transistors are based on the electrical conduction properties of semiconducting materials like silicon and germanium. In particular, the electrical transport in these devices occurs through joints, formed by contact of semiconductor materials, where charge carriers are of different types: voids (type P) or electrons (type N).
electrical conduction properties of the joints are modified depending on the sign and magnitude of the applied voltage, which ultimately played the amplifying effect is obtained with valves: Trading on a joint through a small voltage is able to modify the properties of conducting another joint next to the most important driving voltage.
Initial goals
The transistor is a three terminal device that comes in the Bell Laboratories of AT & T. Is looking for a solid state switch for use in telephony and to replace both relays as bar systems. Then he contemplates the possibility of replacing the vacuum tube. Quentin
Kaiser wrote: "If it were not for the microwave or UHF radar, probably never would have had the need for crystal detectors. If we had not obtained crystal detectors, might not have had the transistor, except that had been developed in a way completely different. "(Quoted in" Miniature Revolution "by E. Braun and S. Macdonald).
physical
was known that the contact between a metal wire and galena (lead sulfide) allowed the passage of current in one direction, as revealed by the work of Ferdinand Braun. The radar, on the other hand, when using high frequencies, a detector should be used efficiently, with little electrical capacity, so it was not convenient to use the vacuum diode. The solid state diode was essential for this purpose. In the forties was complete the theoretical study of semiconductor-metal contacts.
One of the inventors of the transistor, Walter Brattain, wrote: "No one in the profession was sure the analogy between a copper oxide rectifier and a vacuum tube diode, and many had the idea of \u200b\u200bhow to get to a grid A third electrode, to an amplifier. "
to modify the behavior of some semiconductors, took into account the energy levels quantified atoms, giving rise to bands of energy when atoms are regularly distributed. The study of motion of electrons in these bands, suggest the possibility of changing the electrical conductivity of some semiconductors by adding impurities properly controlled, thus resulting in N-type material and type P.1
Source the name
While diode arises when attaching a material with a P N, the transistor arises from a union of type NPN or PNP. The name "transistor" was suggested by JR Pierce, who said: "... and then, at that time, the transistor was thought to be the dual vacuum tube, so if you had a vacuum tube transconductance, it must have transresistance, so I suggest "transistor".
Patents
For patents, made after the first test, was kept secret for almost seven months until it could spell properly functioning . This patent was awarded to John Bardeen and Walter Brattain for the transistor contact tip. The patent junction transistor, which appeared in 1951, was granted to William Shockley. On the latter transistor, E. Braun and S. Macdonald writes: "It is amazing that Shockley had formulated the theory of the junction transistor requires at least two years before the device was produced."
elemental behavior
We can get an idea of \u200b\u200bthe behavior of transistor using a circuit that uses a DC source, a power indicator (ammeter) and two resistors to their respective switches. These resistors be connected between the collector and base, while the source is connected between collector and emitter.
With both switches open, there is no base current and the power indicator, located off the fountain, make a zero current. If we close one of the switches, will base current and collector. If both switches closed, the greater the flow of current. Hence we can say that the transistor behaves like a resistor whose resistance is controlled by the base current.
Inventions
Ten years after the invention of the first transistor saw tremendous advances in this field:
- were invented different types of transistors (for point , junction, field), based on different basic properties,
- different materials were used initially germanium (1948) and subsequently the silicon (1954), which dominates today's semiconductor industry;
- was able to build a large number of transistors, other elements and circuits can be mounted directly on a silicon wafer, to which was given the name of an integrated circuit (1958).
In these first integrated circuits, transistors have typical dimensions of about 1 cm. In 1971 the Intel 4004 chip had about 2000 transistors, while today, an "old" Pentium IV has 10 million transistors, with typical dimensions of about 0.00001 cm. Since 1970, a year and a half, the transistor dimensions were reduced by half (Moore's Law). If it makes them even smaller tecnoilogía using the current no longer work as expected, begin to manifest as the laws of quantum mechanics. To progress further, has developed a new generation of microprocessors based on the properties of matter manifested in the nanoscale.
All these developments respondents in each case to attempt to solve a specific problem attacked both theoretically and experimentally. Many of the physicists who participated in this adventure of the transistor and its later developments gave rise to new inventions (and companies like Texas Instruments, Intel and AMD) that today dominate the scene in which they develop information technologies and communications.
CRF
Lenny Perez M. Z
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