It is an electronic component mainly used for amplification and switching purpose. How a bjt bipolar junction transistor works its all in the doping the way a transistor works can be described with reference to fig. Theory of pn junction diode, diode current equation s. This chapter introduces the bipolar junction transistor bjt operation and then presents the theory of the bipolar transistor iv characteristics, current gain, and output conductance. Bipolar transistors conduct current using both electrons and holes in the same device. The bipolar junction transistor bjt was the first solidstate amplifier element and started the solidstate electronics revolution. A bipolar junction transistor bipolar transistor or bjt is a type of transistor that uses both electrons and holes as charge carriers. Bipolar junction transistors electronics assignment help. Field effect transistors are unipolar devices using one or either type of charge carrier. An npn transistor has an n type emitter, a p type base and an n type collector while a pnp transistor has a. In an npn transistor, the three terminals are named the emitter first nblock, the base pblock, and the collector second nblock. As the name suggests, it is composed of two junctions called emitterbase junction and collectorbase junction. Most notably there is cmos, but see also discrete complementary jfets. Complementary transistor pairs occur beyond bipolar junction transistors.
Basic bipolar transistor theory the basic bipolar transistor or bjt is two diodes constructed back to back on a piece of silicon. In electronics, vacuum tube triodes were used almost for half a century before the bjts. The theory and labeling of the terminals is a little different for the jfet. Jan 09, 2020 multiple choice questions and answers by sasmita january 9, 2020. Applications of bipolar junction transistor or bjt. A bipolar junction transistor bjt is formed by joining three sections of alternating p and ntype material. Bipolar junction transistor bjt function is usually considered in terms of currents. Bipolar junction transistorbjt transistor theory page browsing. The need for a large offstate blocking voltage and high onstate currentcarrying capability is responsible for the changes in structure over the logiclevel counterpart. The schematic symbols are shown in figure belowa and d. Operation of a bipolar transistor as a current amplifier requires that the collectorbase junction be reverse biased and the emitterbase junction be forward biased.
In addition to reading the questions and answers on my site, i would suggest you to check the following, on amazon, as well. It uses different semiconductor materials to the emitter and base region and produces heterojunction. This is the multiple choice questions in bipolar junction transistors from the book electronic devices and circuit theory 10th edition by robert l. I think there is a case for an overview article complementary transistor pair and a case for complementary bipolar junction transistor pair as a separate article. Highlevel injection and heavy doping induced band narrowing are introduced. These semiconductor materials can either be a p type positive with an excess of holes, or a n type negative with an excess of electrons. Transistors are three terminal active devices made from different semiconductor materials that can act as either an insulator or a conductor by the application of a small signal voltage. V i of the emitter base voltage changes the barrier height and the emitter electric current by. Submit your answers but dont be disappointed if you get answers wrong. Of the four regimes, the active or normal mode where the emitter base junction is forward biased and the collector base junction is reverse biased is the most important.
How to use bjt bipolar junction transistor beginners. Bipolar junction transistor amplifier now as the input voltage is changed a little, say. Bjts are available both alone or packaged into integrated circuits ics. Each layer forming the transistor has a specific name, and each layer is provided with a wire contact for connection to a circuit. Bardeen, brattain and shockley, while at bell laboratories, invented it in 1948 as part of a postwar effort to replace vacuum tubes with solidstate devices. Still, it was two more years before bell labs scientists and engineers developed processes that allowed his junction transistor to be manufactured. The vertical power bipolar junction transistor bjt has a fourlayer structure of alternating ptype and ntype doping as shown in figure 7. In normal operation the baseemitter junction is forward biased and the basecollector. The three terminals of the bjt are the base, the collector and the emitter.
Transistors are current controlled solidstate devices that conduct current in proportion to an input current. Today, i am going to discuss the details on the introduction to bjt bipolar junction transistor. Build something learning to mathematically analyze circuits requires much study and practice. Introduction to bjt bipolar junction transistor the. The transistor type npn or pnp can be determined using a multimeter. Bipolar junction transistors ac analysis equations. Bipolar junction transistors bjt general configuration and definitions the transistor is the main building block element of electronics. Bjt bipolar junction transistor are widely used an amplifier, oscillator, switch etc. Find the right answer and learn about transistors as you go. Bjts are widely used in amplifiers for a large amount of everyday electronic. The most useful and the one which contains the most information is the output. Apr 27, 2018 theory of pn junction diode, diode current equation s. Multiple choice questions and answers by sasmita january 9, 2020.
In essence, it describes the amplifying power of the transistor. To become familiar with the theory of operation of bipolar junction transistors bjt and to examine the vi characteristics of bjts. A transistor differs from a pair of back to back diodes in that the base, the center layer. The dc characteristics of bjts can be presented in a variety of ways. Applications of bipolar junction transistor or bjt history. The hetero bipolar junction transistor is also a type is the bipolar junction transistor.
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. Theyre critical as a control source in just about every modern circuit. A bipolar junction transistor or bjt is a three terminal electronic device that amplifies the flow of current. Another kind of transistor is the junction field effect transistor of jfet. In this tutorial well introduce you to the basics of the most common transistor around. It can be formed from a bar of material that has been doped in such a way that it changes from n. Bipolar junction transistors solidstate device theory. The test checks the polarity of the baseemitter and basecollector. Bipolar junction transistor physics and radioelectronics. A bipolar junction transistor is a specially constructed, threeterminal semiconductor device containing two pn junctions.
A bipolar junction transistor is a three terminal semiconductor device consisting of two pn junctions which is able to amplify or magnify a signal. Here we will describe the system characteristics of the bjt. Multiple choice questions and answers on transistors. Shockley applied for a patent on the junction transistor that june and published his detailed theory of its operation in 1949. There are two varieties, the pnp and the npn, but we will focus on the more common npn configuration. Bjts use two junctions between two semiconductor types, ntype and ptype. Bipolar junction transistor 3 theory of operation 1 the majority of current in a pnp transistor is carried by holes which, being positively charged particles, move in the same direction as conventional current flow in an npn transistor, the majority of current is carried by electrons the theory of operation of an npn transistor is. Bipolar junction transistor characteristics page 3 figure 2. Introduction to bipolar transistors designers guide. Jul 14, 2016 this video demonstrates working of a bipolar junction transistor bjt with its practical applications such as transistor as an amplifier and as a switch with help of animation. Bipolar junction transistor quiz learn about electronics. But the special thing about a transistor the part that makes our twodiode model obsolete is the fact that electrons can easily flow from the ptype base to the ntype collector as long as the baseemitter junction is forward biased meaning the base is at a higher voltage than the emitter.
The fusion of these two diodes produces a three layer, two junction, three terminal device forming the basis of a bipolar junction transistor, or bjt for short. A signal of small amplitude if applied to the base is available in the amplified form. The bipolar junction transistor can be considered essentially as two pn junctions placed backtoback, with the base ptype region being common to both diodes. Sige transistor, transit time, and cutoff frequency are explained. In bipolar junction transistor, electric current is conducted by both free electrons and holes. Dec 02, 2019 this is the multiple choice questions in bipolar junction transistors from the book electronic devices and circuit theory 10th edition by robert l.
Bipolar junction transistors bjt and its applications. The operation of the transistor is very dependent on the degree of doping of the various parts of the. The bipolar junction transistor bjt was named because its operation involves conduction by two carriers. A bipolar npn transistor has a dc current gain, beta value of 200. Still, it was two more years before bell labs scientists and engineers developed processes that allowed his junction transistor to be manufactured in production quantities 1951 milestone. Unipolar transistors, such as fieldeffect transistors, use only one kind of charge carrier. The light bulb invented by thomas edison in the early 1880s was one of the first uses of vacuum tubes for any electrical applications.
In an npn transistor, the three terminals are named the emitter first nblock, the. Bipolar junction transistor bjt theory worksheet discrete. Theory the transistor is a two junction, three terminal semiconductor device which has three regions namely the emitter region, the base region, and the collector region. Bipolar junction transistor bjt theory electrical a2z.
The bipolar junction transistor ii regimes of operation outline regimes of operation largesignal equivalent circuit model output characteristics reading assignment. A bipolar junction transistor bjt is a type of semiconductor that uses both electron and hole charge carriers. Npn transistor tutorial the bipolar npn transistor. V i of the emitter base voltage changes the barrier height and. An npn transistor is a bjt with a thin, lightly doped ptype base region sandwiched between a heavily doped ntype emitter region and a large, lightly doped ntype collector region. Typically, students practice by working through lots of sample problems and checking their answers against those. The bipolar junction transistor is the realworld component of this sandwich. The first bipolar transistor was invented at bell labs by william shockley, walter brattain, and john bardeen so late in 1947 that. The transistor has three terminals labeled collector, base, and emitter. Introduction to bipolar transistors the bipolar junction transistor 6 of 19 the designers guide community 4 the bipolar junction transistor a transistor combines two junctions and has three terminals as shown in figure 7. Bipolar junction transistor bjt semiconductor theory.
Mar 15, 2020 a bipolar junction transistor is a three terminal semiconductor device consisting of two pn junctions which is able to amplify or magnify a signal. A bipolar junction transistor, bjt, gains its name from the fact that it uses both holes and electrons in its operation. This video demonstrates working of a bipolar junction transistor bjt with its practical applications such as transistor as an amplifier and as a switch with help of animation. Before transistors came into existence vacuum tubes were used. Bipolar transistor chapter objectives this chapter introduces the bipolar junction transistor bjt operation and then presents the theory of the bipolar transistor iv characteristics, current gain, and output conductance. Bipolar junction transistor bjt theory discrete semiconductor devices and circuits pdf version.
The transistor on the left is called an npn transistor and the transistor on the right is called a pnp transistor. Learn bipolar junction transistors ac analysis equations and know the formulas for the bipolar transistor configurations such as fixedbias configuration unloaded, voltagedivider bias configuration unloaded and unbypassed emitterbias configuration unloaded. It is a semiconductor device and it comes in two general types. The transistor bjt was not the first three terminal devices. It is a currentdriven device mosfet is voltage driven, the output current is equal to the input current times a factor which is called gain. Jan 06, 2019 history of bipolar junction transistorsthe transistor bjt was not the first three terminal devices. One of the most important properties of the bipolar junction transistor is that a small base current can control a much larger collector current.
Shahram marivani bipolar junction transistor characteristics. An npn transistor can crudely be described, as being made up of a layer of p type semiconductor, sandwiched between two pieces of n type semiconductor. A bipolar transistor, or more exactly a bipolar junction transistor, bjt, has two pn diode junctions which are back to back. A bipolar transistor consists of a threelayer sandwich of doped extrinsic semiconductor materials, either pnp in figure belowb or npn at d. The light bulb invented by thomas edison in the early 1880s was. Recall that a diode consists of a n doped or excess. 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. In this section we will describe the operating principles of an npn transistor. To understand the concept of bipolar junction transistor amplifier, we should look through the diagram of a pnp transistor first. A bipolar transistor can be operated in one of four different regimes dependent upon the bias levels on the two diodes in the transistor.1403 57 260 1403 71 897 371 1465 367 1056 36 1431 1483 778 194 291 711 817 391 983 1493 1301 1017 1116 1343 443 502 155 213 161 661 289 607 708 224