![]() Because of this, virtually all modern processors are designed using CMOS (Complementary Metal Oxide Semiconductor) technology.Ĭompared to a tube, a transistor is much more efficient as a switch and can be miniaturized to microscopic scale. When both NMOS and PMOS field-effect transistors are combined in a complementary arrangement, power is used only when the transistors are switching, making dense, low-power circuit designs possible. That in turn changes that area to behave as if it were P-type silicon, creating a path for current to flow and turning the transistor “on.” When a negative voltage is placed on the gate, the gate electrode creates a field that repels electrons from the N-type silicon between the source and drain. P-type silicon is used for the source and drain, with N-type silicon positioned between them. ![]() That in turn changes that area to behave as if it were N-type silicon, creating a path for current to flow and turning the transistor “on.”Ī PMOS transistor works in a similar but opposite fashion. When a positive voltage is placed on the gate, the gate electrode creates a field that attracts electrons to the P-type silicon between the source and drain. Normally there is no current flow between N-type and P-type silicon, thus preventing electron flow between the source and drain. The gate is positioned above the P-type silicon, separating the source and drain, and is separated from the P-type silicon by an insulating layer of silicon dioxide. An NMOS transistor is made by using N-type silicon for the source and drain, with P-type silicon placed in between. MOSFETs have three connections, called the source, gate, and drain. Silicon doped with boron is called P-type (positive) because it lacks electrons, whereas silicon doped with phosphorus is called N-type (negative) because it has an excess of free electrons. ![]() MOSFETs can be constructed as either NMOS or PMOS types, based on the arrangement of doped silicon used. The composition and arrangement of the different types of doped silicon allow them to act both as a conductor or an insulator, which is why silicon is called a semiconductor. Some of the layers contain silicon with certain impurities added by a process called doping or ion bombardment, whereas other layers include silicon dioxide (which acts as an insulator), polysilicon (which acts as an electrode), and metal to act as the wires to connect the transistor to other components. MOSFETs are made from layers of materials deposited on a silicon substrate. ![]() Today’s small laptop PC (or netbook, if you prefer) and even Tablet PC systems, which run on batteries, have more computing power than many earlier systems that filled rooms and consumed huge amounts of electrical power.Īlthough there have been many designs for transistors over the years, the transistors used in modern computers are normally Metal Oxide Semiconductor Field Effect Transistors (MOSFETs). The conversion from tubes to transistors began the trend toward miniaturization that continues to this day. Because the transistor was so much smaller and consumed significantly less power, a computer system built with transistors was also much smaller, faster, and more efficient than a computer system built with vacuum tubes. The transistor, which essentially functions as a solid-state electronic switch, replaced the less-suitable vacuum tube. Bell associate William Shockley invented the junction transistor a few months later, and all three jointly shared the Nobel Prize in Physics in 1956 for inventing the transistor. The invention of the transistor was one of the most important developments leading to the personal computer revolution.The transistor was invented in 1947 and announced in 1948 by Bell Laboratory engineers John Bardeen and Walter Brattain. ![]()
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