History of Computers - Transistors

--Wirvine 15:13, 7 October 2008 (CDT)By William Irvine

Introduction

In the late 1920's, Julius Lilienfeld, a physicist, filed patents for a three-electrode gadget made of copper sulfide. Lilenfeld's work was the basis for today's field effect transistors, which are used in silicon chips.

A transistor is device used to change electric signals. Transistors are a fundamental piece of modern electronics, are considered by some to be the most important innovation in the twentieth century.

Overview

John Bardeen, William Shockley, and Walter Brattain, scientists at the Bell Telephone Laboratories developed the transistor in an attempt to improve upon the idea of the vacuum tube, which used massive amounts of energy and produces a huge amount of heat. The transistor is a device made of some sort of semi-conducting material, which can both conduct and insulate, allowing the transistor to switch and modulate electric current. The 3 terminal transistor allows modulation of electricity by applying current to the third terminal.

Transistors are composed of three layers of silicon or germanium (which are both semiconductors). In a process known as doping, impurities like boron, gallium, and aluminum are added to each layer to cause each one to have either a net positive or negative charge. Transistors are designed to have either an "NPN" or "PNP" configuration (with P representing a positively charged layer and N representing a negatively charged layer).

Field effect transistors (FETs) have at least three electrodes: a source terminal (where current flows in), one or more gates (which can block or allow electron flow between the source and the drain), and a drain terminal (where current flows out). An FET applies a positive voltage across a gate to create an electric field that allows a thin channel of electrons to flow from the source to the drain, switching the transistor on.

Junctions transistors work by applying a small positive voltage near the source, which makes the source negatively charged and the drain positively charged. This pulls the electrons from the source to the drain and creates a current, switching the transistor on.

Importance

The transistor can be mass produced at astoundingly low per transistor prices, which has led to it being in functionally every electronic device. in 2006 "60 million transistors were made...for every man, woman, and child in the world." Transistors are mostly used in integrated circuits, and have replaced electromechanical devices in controlling devices and appliances. The low cost of transistors and have also reduced the cost of digital computers and increased their power without increasing their size, which leads to the higher digitalization of information, resulting in the Digital Revolution. Before transistors, the vacuum tube was used to represent 1's and 0's, so with the introduction of the smaller and more efficient transistor, more complex calculations can take place within a computer without requiring nearly as much space and time as vacuum tubes would necessitate.

Transistors are also the core component of modern day memory [2]

Links & Resources

http://en.wikipedia.org/wiki/Transistor#Bipolar_junction_transistor http://www.kpsec.freeuk.com/components/tran.htm http://www.kpsec.freeuk.com/trancirc.htm http://nobelprize.org/educational_games/physics/transistor/history/ http://inventors.about.com/library/weekly/aa061698.htm