was the replacement of three-electrode thermionic valve or triode, the bipolar transistor was invented at Bell Laboratories U.S. December 1947 by John Bardeen , Walter Brattain yWillian Bradford, who were awarded the Nobel Prize for Physics in 1956.
At first they used bipolar transistors and then invented the so-called field effect transistors (FET). In the past, the current between the source and loss (collector) is controlled using an electric field (and lost output (collector) lower). Finally, it appeared the metal-oxide semiconductor FET (MOSFET). The MOSFET allowed an extremely compact design, necessary for highly integrated circuits (IC). Today most of the circuits are built with technology called CMOS (complementary metal-oxide semiconductor). CMOS technology is a design with two different MOSFET (n and p-channel MOSFET), which complement each other and consume very little current in no load operation.
The transistor consists of a substrate (usually silicon) and three parts artificially doped (contaminated with specific materials in specific quantities) that form two bipolar junctions, the issuer emitting carriers, the collector that receives or collection and the third, which is sandwiched between the first two, modulates the passage of these carriers ( base). Unlike the valves, the transistor is a current controlled device and obtained amplified current. In the design circuit transistors are considered an active element, unlike resistors, capacitors einductores that are passive. Its operation can only be explained by quantum mechanics.
In simple terms, the current flowing through the "collector" is amplified function that is injected into the "sender", but the transistor graduates only the current flowing through itself, whether from a current source continuously fed to the "base" to circulate the load by the "collector", according to the type of circuit is used. The amplification factor or gain achieved between base current and collector current, the transistor is called Beta. Other parameters to take into account and that are specific to each type of transistor are: Breakdown Voltage Collector Emitter, Base Emitter, Collector Base, Maximum power, heat dissipation, operating frequency, and several tables which are plotted various parameters such as base current, collector emitter voltage, base-emitter voltage, emitter current, etc. The three basic types of schemes use analog transistors are common emitter, common collector and common base.
post-transistor models described, the bipolar transistor (FET transistors, MOSFET, JFET, CMOS, VMOS, etc.) Do not use the current to be injected into the terminal "base" to modulate the emitter current or collector, but the voltage at the terminal door or gate control and graduates channel conductance between source and drain terminals. Thus, the output current in the load connected to the drain (D) will be amplified according to the voltage between the gate (Gate) and source (Source). Its operation is analogous to the triode, except that the equivalent triode gate, drain and source are grating, plate and cathode.
The field effect transistors, are those that have allowed large-scale integration we enjoy today, to have a rough idea can be made several thousand transistors interconnected per square centimeter in several layers.
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