Parasuraman,department of metallurgy and material science,iit madras. The multifold advantages of replacing vacuum tubes with a solidstate device rapidly promulgated its use in applications. Solid state devices iit madras online course video. Up next transistor as an amplifier and as a switch phy duration. Also includes some basic characteristics and parameters of the bjt. Methods of transistor biasing s bharadwaj reddy august 14, 2016 september 27, 2016 in the interest of simplicity and economy, it is desirable that transistor circuit should have a single source of supplythe one in the output circuit i. Introduction to bipolar junction transistors bjt bipolar. Bjts use two junctions between two semiconductor types, n. Bipolar junction transistors bjt and its applications. It is a semiconductor device and it comes in two general types. The hetero bipolar junction transistor is also a type is the bipolar junction transistor. The operation of the transistor is very dependent on the degree of doping of the various parts of the.
Because of this, such junctions are very useful for operation at the frequencies as high as 10 ghz. Each junction can be forward or reverse biased independently. A bipolar junction transistor is a threeterminal semiconductor device that consists of two pn junctions which are able to amplify or magnify a signal. Sep 01, 2008 38 videos play all electronics electronics for analog signal processing i nptelhrd lecture 21 transistor bjt inverter duration. Autoplay when autoplay is enabled, a suggested video will automatically play next. Summary the bipolar junction transistor bjt is constructed of three regions. Lecture 4 outline bipolar junction transistor bjt general considerations structure otii ti d ee105spring 2008 lecture4, slide 1prof. Bipolar junction transistors the transistor is a threelayer semiconductor device consisting of either two n and one p type layers of material or two p and one n type layers of material. Dc operation of bipolar junction transistors bjts there are two types of bjts, the npn and pnp the two junctions are termed the baseemitter junction and the basecollector junction in order for the transistor to operate properly, the two junctions must have the correct dc bias voltages the baseemitter be junction is. Transistor action baseemitter junction is forward biased and collectorbase junction is reverse biased electrons emitted into base much more than holes since the doping of emitter is much higher magic.
Electronic materials, devices, and fabrication by prof s. Bipolar junction transistor npn bjt shown 3 terminals. Smith department of eecs university of california, berkeley eecs 105 spring 2004, lecture 22 prof. These can have the configuration of npn or pnp and the various layers can either be. Applications of bipolar junction transistor or bjt. Bipolar junction transistors emitter p n collector base pnp transistor emitter n p base npn transistor bipolar. The base current i b controls the collector current i c. The transistor bjt was not the first three terminal devices.
Before transistors came into existence vacuum tubes were used. In electronics, vacuum tube triodes were used almost for half a century before the bjts. Radhakrishna rao, department of electrical engineering,iit madras. Nptel provides elearning through online web and video courses various streams. Today, i am going to discuss the details on the introduction to bjt bipolar junction transistor. It is a type of transistor that uses both electron and hole charge carriers. Bipolar junction transistor bjt few most important applications of transistor are. The bipolar junction transistor bjt was named because its operation involves conduction by two carriers. Upon completion of the presentation you will be able to understand. The operation of npn and pnp transistors are same if the roles played by the electrons and holes are interchanged. The point contact junction has very low value of the capacitance. The early voltage va has a typical value of 150 volts. These regions essentially form two backtoback pn junctions in the same block of semiconductor material silicon.
Bipolar junction transistors pdf 46p download book. One pn junction of a transistor is reversebiased, whereas the other is forwardbiased. A bipolar junction transistor, or bjt, is a type of transistor in which the current flow between the collector and the emitter is controlled by the amount of current that flows through the base. The light bulb invented by thomas edison in the early 1880s was one of the first uses of vacuum tubes for any. A bipolar junction transistor bjt consists of three differently doped re gions. The three layers are called the emitter, base and collector. The bipolar junction transistor bjt is an active device. Bipolar junction transistor 2 general construction a bipolar junction transistor consists of two pn junctions in close proximity to each other two arrangements are possible according to whether the middle region is n or ptype material npn or pnp leads are attached to the three regions, known as emitter, base, and. The transistor is the main building block element of electronics it is a semiconductor device it is a three terminal device two basic families of transistors are. Bipolar junction transistors transistor operation the biasing of the two types of transistor has been illustrated in the figures. Introduction to bjt bipolar junction transistor the. It uses different semiconductor materials to the emitter and base region and produces heterojunction. Bipolar junction transistor working, definition, application. Introduction to bipolar junction transistor bjt slideshow.
There is no conduction between the collector and the emitter. A bipolar transistor consists of a threelayer sandwich of doped extrinsic semiconductor materials, a and c either pnp or npn b and c. Here we will describe the system characteristics of the bjt. These videos are provided by nptel elearning initiative. Unipolar transistors, such as fieldeffect transistor s, use only one kind of charge carrier. The hbt can handle the singles of very high frequencies of several hundred ghz generally it is used in ultrafast circuits and mostly used in radiofrequency. Bipolar junction transistors tlt8016 basic analog circuits 20052007 11 distortion figure 4. Bipolar junction transistors bjt transistor basics a bipolar junction transistor is a three layer npn or pnp semiconductor device. Bipolar junction transistor bjt field effect transistor fet transistors are used in. There are two basic types of bipolar transistor construction, pnp and npn, which basically describes the physical arrangement of the ptype and ntype semiconductor materials from which they are. How a bjt bipolar junction transistor works its all in the doping the way a transistor works can be described with reference to fig. There are two junctions in bipolar junction transistor. Bjt bipolar junction transistor construction, types and.
A bipolar junction transistor bipolar transistor or bjt is a type of transistor that uses both electrons and holes as charge carriers. It is an electronic component mainly used for amplification and switching purpose. There are three terminals in bipolar junction transistors are explained below. Electronic current is conducted by both free electrons and holes in bipolar junction transistor. Lecture 3 bipolar junction transistor bipolar junction. Power bipolar junction transistor bjt background the bipolar junction transistor was invented in 1947 by shockley, brattain, and bardeen. The word transistor is a combination of the two words trans fer var istor which describes their mode of operation way back in their early days of electronics development.
Solid state devices electronics and communication engineering course from iit madras nptel lecture videos by prof. The bipolar junction transistor ii regimes of operation outline regimes of operation largesignal equivalent circuit model output characteristics reading assignment. Equivalent to an on state when transistor is used as a switch. Bipolar junction transistors solidstate device theory. The three terminals of the bjt are the base, the collector and the emitter. Each layer forming the transistor has a specific name, and each layer is provided with a wire contact for connection to a circuit. Smith context in fridays lecture, we discussed bjts bipolar junction transistors today we will find large signal models for the bipolar junction transistor, and start exploring. The bjt has two pn junctions, the baseemitter junction and the basecollector junction. And the saturation current is a very small number, typically about 1 times 10 to the minus 15 amps.
Collector npn transistor pnp transistor p n p n p n. Bipolar junction transistors bjt general configuration and definitions the transistor is the main building block element of electronics. Bipolar junction transistors bjts the bipolar junction transistor is a semiconductor device constructed with three doped regions. Basic construction, biasing and operation of npn and pnp type transistors. Unlike a normal pn junction diode, this transistor has two pn junctions. The first bipolar transistor was invented at bell labs by william shockley, walter brattain, and john bardeen so late in 1947 that it was not published until 1948. Bjt circuit analysis pdf currently this section contains no detailed description for the page, will update this page soon. Bipolar junction transistor theory pdf 27p currently this section contains no detailed description for the page, will update this page soon. Solid state devices lecture 20 heterojunctionbipolar. Introduction, semiconductor, equilibrium carrier concentration, carrier transport, excess carriers, pn junction, procedure for device analysis, bipolar junction transistor bjt, metaloxidesemiconductormosjunction, mos field effect transistor mosfet.
Bipolar junction transistor 1 by basic electronics. In summary, during this lesson i introduced the bipolar junction transistor, a three terminal device that consists of two pn injunctions. Lecture 3 bipolar junction transistor free download as powerpoint presentation. The availability of singlecrystal silicon technology with higher purity levels together. Most electrons cross the base junction and are swept into collector why.
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