Transistors and Moore`s Law Unit

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TRANSISTORS

Transistorsand Moore’s Law

Unit

Whatis a transistor?

Transistors are common devicesfound in most electric gadgets mounted on various surfaces such assilicon and are used to switch or amplify electric signals. Inventedin by John Bardeen, Walter Brattain, and William Shockley in 1947, atransistor is usually made up of three layers of semiconductormaterial that relay currents (Amos, 2013). As an amplifier ofelectric signals, a small change in the input signal leads to abigger change in the output signal. As a switch, a transistor is usedto function in only two states, ‘on’ and ‘off’. In the ‘on’state, the transistor is conductive and has a significant draincurrent while in the ‘off’ state, the transistor isnon-conductive and it has very low drain current. Althoughtransistors are mainly used for amplifying and switching electricsignals, they can be used in switching to another part of a circuitin case of a change in resistance to electric signal is detected. Thus there are three main types of transistors namely bipolar, fieldeffect (FET) and thyristors/bistables.

The bipolar transistors were themost dominant in the early years of production. They arecharacterized by three leads comprising of emitter, collector andbase. Figure 1(a) below shows a bipolar transistor and the generaldesign for (Transistors 2014).

Figure1 (a)A bipolar transistor(b) general transistor design

TheField-effect transistors (FETs) are digital switches that controlflow of current. They are of various forms and are characterized bythree leads of gate, drain and source as figure 2 shows (Transistors2014). .

Figure2 Field-effect transistor

Thethyristors/bistables transistors are similar to FETs only that unlikeFETs, they remain on even after source voltage is stopped. For thisreason, they are used to create latching circuits, thus are common inalarm systems (Transistors 2014). Thyritors also have three leads ofanode, cathode, and gate like the others as figure 3 shows.

Figure3 A thyristor transistor

Moore’sLaw

Moore’s law is a law in thecomputer world that arose in the 1965 and named after one of IntelInc.’ co-founders, Gordon Moore, who proposed the theory. The lawstates that the number of transistors mounted on an affordable CPUwould double every two years (Fuelling the innovation, 2014). It wasexpected that the doubling of the number of transistors on the CPUwould lead to doubling of speeds. As such, the law motivated playersin the industry to develop smaller and energy efficient transistorsat even lower costs. For instance, in 2000 the number of transistorsin a modest CPU numbered 37.5 million, while in 2009 the number wentup to 904 million. However, speeds have not doubled as the speedsfrom 2000 to 2009 ranged 1.3 GHz to 2.8 GHz. (Moore’s law, n.d.)

Whatis the problem? Why is it challenging?

The problem in development ofsmaller and more energy efficient transistors lies in the materialsused. This is because devices that rely on CPUs or chips are growingsmaller and thus the need for even smaller and more transistors beingfitted in the small CPU’s grows. The future of technology lies inthe ability of the modern players in the field to develop fastercomputers with greater processing speeds. However, development oftransistors holds the key to the future mainly based on thesemiconductor material used. Researchers have called this the ‘redbrick wall’. Currently, the materials used are metal oxides andsilicon. However, the use of very thin wires (metal oxide) in anattempt to reduce the size of transistors leads to increasedelectrical resistance and overheating thereby limiting the speeds ofchips (Markoff 2015).

The problem is challenging becauseresearch has yet to identify materials that can be used in the placeof metal oxides that will allow for the creation of small transistorswithout increasing resistance and heat. Any material that should besued in transistors should have the right atomic structure to attaina desired level of conductivity. Alternative materials to siliconinclude germanium and gallium arsenide, which can attain higherspeeds but is very expensive for mass production.

Solution

The solution to this the red brickwall and the desire for smaller and faster processors can beaddressed mainly through identifying alternative materials to maketransistors. While researchers have suggested new different ways toconnect ultrathin metal wires to the nanotubes to reduce transistorsize without affecting conductivity, the ultimate solution will isbased nanotechnology. By developing transistors made of single atoms,it will allow researchers to develop the tiniest transistors ever andpossibly bring to an end Moore’s law given that the smallestparticle of matter is an atom. Transistors made from phosphorousatoms would deliver the desired conductivity and also be in verysmallest size possible (One and done 2012). The possible design forsuch an alternative would be as shown in figure 4 below.

Figure4 A design sketch for a single phosphorous atom transistor

Whatare the challenges for your solution?

Themain challenge is that the single phosphorous atom gets hot quickly,but that could be solved by using coolants to manage the temperature.This option was developed by an international team of researcher andthey are yet to be developed it for use in computers. Again, thecurrent nanotechnology available has a long way to go before it canbe used to develop single atom transistors for mass use in computersand other devices.

References

Amos,S. (2013). Principles oftransistor circuits: introduction to the design of amplifiersreceivers and

digitalcircuits. New York:Elsevier.

Fuellingthe innovation we love and depend on: 50 years of Moore’s law(2015). Retrieved from,

http://www.intel.com/content/www/us/en/silicon-innovations/moores-law-technology.html

Markoff,J. (Oct 1st2015). One and done: Single-atom transistor is end of Moore`s Lawmay be

beginningof quantum computing. NewYork Times.

Moore’slaw (n.d.). Retrievedfrom http://www.mooreslaw.org/

Oneand done: Single-atom transistor is end of Moore`s Law may bebeginning of quantum computing

(2012). Purdue University.Retrieved fromhttp://www.purdue.edu/newsroom/research/2012/120219KlimeckAtom.html

Transistors(2014). Retrieved from

http://www.bbc.co.uk/schools/gcsebitesize/design/electronics/switchesrev3.shtml

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