Sumit thakur ece seminars transistor ppt powerpoint presentation pdf. The npn transistor has three terminals emitter, base and collector. The first highfrequency transistor was the surfacebarrier germanium transistor developed by philco in 1953, capable of operating up to 60 mhz. This is because the baseemitter junction behaves like a diode and a diode has a constant voltage drop when biased in the forward direction. Earlier, the critical and important component of an electronic device was a vacuum tube. Bipolar junction transistor physics and radioelectronics. Theyre critical as a control source in just about every modern circuit. The collector base junction is reverse biased and its resistance is a bit higher.
A small forward bias is sufficient at the emitter junction whereas a high reverse bias has to be applied at the collector junction. The transistor as its names suggests transfer resistance from one channel to other channels. Generally the npn transistor is the most used type of bipolar transistors because the mobility of electrons is higher than the mobility of holes. The break down voltage of a transistor with its base open is bv ceo and that with emitter open is bv cbo, then a bv ceo bv cbo b bv ceo bv cbo c bv ceo transistor construction. Transistors are identified by a joint army case of the transistor. The ratio of these two currents is of the order of 15 to 100.
The device operates similar to the hot electron transistor. To overcome this problem we make one terminal of the transistor common to both input and output terminals. P517617 lec 5, p7 transistors transistors are the heart of modern electronics replaced vacuum tubes voltage and current amplifier circuits high frequency switching computers impedance matching low power small size, can pack thousands of transistors in mm2 in this class we will only consider bipolar transistors. The letter n following the first number indicates a semiconductor.
Bipolar junction transistor bjt basics gate problems one mark questions 1. The value of beta for most standard npn transistors can be found in the manufactures data sheets but generally range between 50 200 the equation above for beta can also be rearranged to make ic as the subject, and with a zero base current ib. Semiconductors, diodes and transistors 10 video education australasia pty ltd 2011 reproducing these support notes you may download and print one copy of these. This is because the base emitter junction behaves like a diode and a diode has a constant voltage drop when biased in the forward direction. Using these 3 terminals the transistor can be connected in a circuit with one terminal common to both input and output in a 3 different possible configurations.
Npn transistor tutorial the bipolar npn transistor. These were made by etching depressions into an ntype germanium base from both sides with jets of indiumiii sulfate until it was a few tenthousandths of an inch thick. In bipolar junction transistor, electric current is conducted by both free electrons and holes. Npn transistor circuit working, characteristics, applications. Indium electroplated into the depressions formed the collector. Base b transistor basics emitter to base junction is forward biased normally collector to base junction is reverse biased normally transistors are current operated devices, so kcl should be applied first. Bipolar junction transistor bjt basics gate problems. One is the emitterbase junction, and the other is collector base junction. For the sake of understanding, let us consider npn transistor in cb configuration. The break down voltage of a transistor with its base open is bv ceo and that with emitter open is bv cbo, then a bv ceo bv cbo b bv ceo bv cbo c bv ceo electronics. A transistor has 3 terminals, the emitter, the base and the collector. If in doubt about a transistor s markings, always replace a transistor with one having identical markings, or consul that an identical replacement or substitute is used.
The bipolar power transistor is a three layer npn or pnp device within the working range, the collector current ic is a function of the base current ib, a change in the base current giving a corresponding amplified change in the collector current for a given collector emitter voltage vce. The 2 or 3digit number following the letter n is a serialized identification number. Typically a thin wafer of germanium was used for the base of the transistor. The three regions of the bjt are known as emitter, base, and collector. Semiconductors module 3 bipolar junction transistors semiconductors module 3 pdf 2 e. The graphene base transistor gbt is a very promising device concept for analog applications.
The vacuum tubes worked but they are bulky, require higher operating voltages, high power consumption, yield lower efficiency, and cathode electronemitting materials are used up in operation. Junction transistors bjts there are two types of bjts, the npn and pnp the two junctions are termed the base emitter junction and the base collector junction in order for the transistor to operate properly, the two junctions must have the correct dc bias voltages the base emitter be junction is forward biased. A bipolar junction transistor or bjt is a three terminal electronic device that amplifies the flow of current. In this tutorial well introduce you to the basics of the most common transistor around. Introduction to transistors types, baising modes and.
The values of beta vary from about 20 for high current power transistors to well over for high frequency low power type bipolar transistors. The transistor is a three semiconductor current controlled device. The transistor is a terminal device and the three terminals are base, emitter, and collector. Basic electronics transistor configurations tutorialspoint. Thus, as there are three terminals of the transistor, i. Transistor has three terminals emitter, base, and collector. The common base connection for both npn and pnp transistors is as shown in the following figure. The npn transistor is mostly used for amplifying and switching the signals. Base, emitter and collector but when we connected it in a circuit, we require four terminals. You can use atransformer to amplify either current or voltage, but you have to trade off the other. When the emitter voltage is applied, as it is forward biased, the electrons from the negative terminal repel the emitter electrons and current flows through the.
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