These equations are based on the transport model for a bipolar junction transistor. It is an electronic component mainly used for amplification and switching purpose. Understanding the application of a bipolar junction transistor or bjt as a switch requiers understanding the general working principles behind a transistor and the specific working principles behind a bjt. Obtain a copy of a datasheet for a smallsignal transistor such as the 2n2222. Bipolar transistors are amongst the most widely used devices for amplification of all types of electrical signals in discrete circuits, i. It is obvious that this is not the case with the transistor in active region. The bipolar junction transistor, the first type of transistor to be massproduced, is a combination of two junction diodes, and is formed of either a thin layer of ptype semiconductor sandwiched between two. The ebersmoll model is an ideal model for a bipolar transistor, which can be used, in the forward active mode of. Then bipolar transistors have the emitterbase junction ebj,collectorbase ability to. The name bipolar indicates that two types of charge carriers are involved in the working of a bjt. The transistor will operate as an amplifier or other linear circuit if the transistor is biased into the linear region. As we have seen a semiconductor offer less resistance to flow current in one direction and high resistance is another direction and we. Bipolar junction transistors as switches this worksheet and.
A bipolar junction transistor bipolar transistor or bjt is a type of transistor that uses both electrons and holes as charge carriers. Simplified cross section of a planar npn bipolar junction transistor. A transistor is essentially a semiconductor device with physical properties that make it ideal for amplifying. Today, i am going to discuss the details on the introduction to bjt bipolar junction transistor. Saturation voltage availability product name optimum point of response ir switch 0. The bipolar junction transistor can be considered essentially as two pn junctions placed backtoback, with the base ptype region being common to both diodes. Bipolar transistors are current regulating devices that control the amount of current flowing through them in proportion to the amount of biasing voltage applied to their base terminal acting like a currentcontrolled switch. In the case of both devices, we will talk about the nonlinear models, load line analysis and applications. The symbol for the npn transistor is bipolar transistors have three terminals. Basics bjt fabrication slide slide 14 npn transistor band diagram. The bipolar junction transistors bjt, is one of the oldest but most famous. Experiment 6 transistors as amplifiers and switches our final topic of the term is an introduction to the transistor as a discrete circuit element.
The transistor as a switch bipolar junction transistor. Bipolar junction transistors bjt general configuration and definitions the transistor is the main building block element of electronics. The principle of operation of the two transistor types. Objectives describe the basic structure of the bipolar junction transistor bjt explain and analyze basic transistor bias and operation discuss the parameters and. Pdf on feb 24, 2018, shree krishna khadka and others published bipolar junction transistor find, read and cite all the research you need on researchgate.
How to diagnose a circuit board with a bad transistor. Transistor switches can be used to switch and control lamps, relays or even motors. In this episode of electronic basics i will show you how to use npn and pnp bipolar junction transistors as switches in order to turn on and off your electronic load with a control signal. Bipolar junction transistors also known as bjts can be used as an amplifier, filter, rectifier, oscillator, or even a. As we will go through the topic, we will know about the transistor, mainly bipolar junction transistor or bjt.
A relatively small flow of electrons sent through the base of the transistor has the ability to exert control over a. Then we can define the saturation region or on mode when using a bipolar transistor as a switch as being, both junctions. Bjt regions bipolar junction transistor transistor. Describe the basic operation of a silicon planar transistor.
How to use bjt bipolar junction transistor beginners. The above diagram show a typical microcontroller interface circuit using npn transistor. When used as an ac signal amplifier, the transistors base biasing voltage is applied in such a way that it always operates within its active region, that is the linear part of the. Pdf on feb 24, 2018, shree krishna khadka and others published. Next we will talk about diodes, followed by the bipolar junction transistor. Since an integrated circuit is constructed primarily from. Objectives describe the basic structure of the bipolar junction transistor bjt explain and analyze basic transistor bias and operation discuss the parameters and characteristics of a transistor and how they apply to transistor circuits discuss how a transistor can be used as an amplifier or a switch troubleshoot various failures typical of transistor circuits. The manufacture of the transistor can bebetween the relative insertion phase length of trqnsistor transistor and fluctuations in a number of variablesactive base. Bipolar transistor bipolar transistor basics in the diode tutorials we saw that simple diodes are made up from two pieces of semiconductor material, either silicon or germanium to form a simple pnjunction. Solid state switches are one of the main applications for the use of transistor to switch a dc output on or off. Bipolar junction transistors also known as bjts can be used as an amplifier, filter, rectifier, oscillator, or even a switch, which we cover an example in the first section. Practical electronicsbipolar transistors wikibooks.
Almost in many of the applications these transistors are used for two basic functions such as switching and amplification. When used as an amplifier, the baseemitter junction is forward biased. Saturation characteristics transistor switch in saturation 7. To minimize the fraction of carriers that recombine before reaching the collectorbase junction, the transistors base. Bipolar junction transistors bipolar transistors work as currentcontrolled current regulators. A wide variety of all transistor options are available to you, such as bipolar junction transistor, pentode transistor, and triode transistor. See also fieldeffect transistor fieldeffect transistor and transistor. Calculate the base current ib required to switch a resistive load of 4ma. Introduction to bjt bipolar junction transistor the.
The word transistor is derived from the words transfer and resistor it describes. The bipolar junction transistor or simply bjt is a three layer, three terminal and two junction semiconductor device. In this article, the basic overview of transistors switching theory and the basic pnp and npn transistor working as switch, applications. The inner workings of an npn bipolar junction transistor. Saturation the transistor is fullyon operating as a switch and ic. Almost in many of the applications these transistors are used for two.
Transistor switches can be used to switch a low voltage dc device e. Experiment 6 transistors as amplifiers and switches. Bjt regions free download as powerpoint presentation. In this picture, i c is independent of v bc and v ce as long as v be v t i c i s e 0. Bjt bipolar junction transistor are widely used an amplifier, oscillator, switch etc. Then to summarise when using a transistor as a switch the following conditions apply. Unipolar transistors, such as fieldeffect transistors, use only one kind of. In the case of a transistor, the component is made to act as either a switch or an amplifier of electric current as a result, a transistors failure can. The bipolar junction transistor bjt as a switch all about circuits. If the circuit uses the bipolar transistor as a switch, then the biasing of the transistor, either npn or pnp is arranged to operate the transistor at both sides of the. Bipolar junction transistors bjt and its applications. Basics bjt configurations bipolar junction transistors. Another kind of transistor is the junction field effect transistor of jfet. Bipolar junction transistors types of bipolar junction transistors.
It is a semiconductor device and it comes in two general types. Bipolar junction transistors bipolar junction transistor. Most of the parts could be shipped out within 3 days after payment have been confirmed. The ebersmoll model of an npn bipolar junction transistor two dependent current sources are used to indicate the interaction of the junctions. This pn junction is generally either a diodeconnected bipolar junction transistor or, february 2002 typical pnp bipolar transistor used as remote sensor twistedpair cable e p. The pnp bipolar transistor block uses a variant of the. The basic bipolar transistor or bjt is two diodes constructed back to back on a piece of silicon. Hence, the transistor is called a bipolar junction device just like a diode, a transistor needs to be biased to conduct or nonconduct. Bipolar junction transistor as a switch iosr journal.
This is a quick tutorial for teaching students of elec 2210 how to use multisim for bipolar transistor circuit simulation. Note that because it is a particular type of transistor, the primary applications of bjt center on either amplifying electronic signals or switching. Chapter 10 bipolar junction transistors transistors as. It is a currentdriven device mosfet is voltage driven, the output current is equal to the input current times.
Choose the right type of bipolar junction transistor for each of these switching. Bipolar junction transistors, electronic components. This page was last edited on 15 augustat the 2n is a commonly available pnp bipolar junction transistor used for general purpose lowpower amplifying or switching applications. Chapter 10 bipolar junction transistors transistors as amplifiers and switches from ece 405 at new jersey institute of technology. Cn100 datasheet, equivalent, cross reference search. Working of transistor as a switch npn and pnp transistors. When used as an amplifier, the baseemitter junction is forwardbiased. Bipolar transistor bipolar transistor bipolar transistor. In a real transistor, the region of the two p regions is very narrow or thin so that the carriers can diffuse across the region freely.
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