RC R1 VCC C1 vo R2 vi RE Figure 1. . How to Calculate the Base Current, I B, of a Transistor. BJT is a current controlled device. Each method of connection responding differently to its input signal within a circuit as the static characteristics of the transistor vary with each circuit arrangement. The NPN transistor is made by placing a p-type material between two n-type materials. Transistors are used to amplify current and so in an examination you could be asked to find the BASE current or COLLECTOR current or the GAIN. TRANSISTOR AND AMPLIFIER FORMULAS 301 Collector substrate C cs D C cso [1 V sc/ os]1/2 Transition frequency f T D 1 2 g m C CC Thermal voltage V T D kT q D 0.259 V FET Symbols NMOS Depletion. They're critical as a control source in just about every modern circuit. h�bbd``b`� $� �n ��$� $�� F=�H����OAD8HL HpG�L �_�D�6 ������ �``� ��/�;� �#O A bipolar junction transistor, shortly termed as BJT is a current controlled device that consists of two PN junction for its function. These formulas, we can use in Excel 2013. With Re. There are several ways to find the base current, IB, of a transistor.And it all depends on what information is already known about the transistor: x��Z[o�F~�_1��������"u����6F��Z�cn%Q�x����9�F)����9�̹|ߌ���ӿ���`T)N �y��gz��7����ͿjC��Q'Z�4�w���7�~�h���rGo����Pcz��׿�(�/�=��3ך��|��I?�+r�_��Li���'LL����{,)�Sj��=���Kܝ�CUTuy����qW�����u�d�*d��b�:rS��偾�u��ƅ���W��������`Ʉ��������� �i�����{ʥ�*�^��G�#�>5 Cumple funciones de amplificador, oscilador, conmutador o rectificador. Common Base Configuration – has Voltage Gain but no Current Gain. Also, IS is not a well-defined transistor parameter. Formulas, Tables and Basic Circuits LED CURRENT LED VOLTAGE DROP Forrest M. Mims 111 . It is convenient to use the existing VCC supply instead of a new bias supply. Basic transistor … 1 0 obj Bipolar Junction Transistors (BJT): Part 4 Small Signal BJT Model Reading: Jaeger 13.5-13.6, Notes . Experiment: Transistor Circuit Design. β β − = ++ Without Re. Note the resistor from the base to the battery terminal. 2016 as well as 2019. It is configured in two ways as NPN and PNP. The most widely used circuit is the common emitter where the emitter is common to both input and output circuits. ECE 3050 Analog Electronics - BJT Formula Summary Equations are for the npn BJT. The base current, IB, of a transistor is a crucial current of a bipolar junction transistor.Without this base current, the transistor can't turn on. As the Bipolar Transistor is a three terminal device, there are basically three possible ways to connect it within an electronic circuit with one terminal being common to both the input and output. The mobility of an electron in the conduction band is greater than that of the hole (or electron) in the valence band. << /Length 26 0 R /Type /XObject /Subtype /Image /Width 265 /Height P517/617 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. In the previous tutorial we saw that the standard Bipolar Transistor or BJT, comes in two basic forms. Formulas, Tables and Basic Circuits LED CURRENT LED VOLTAGE DROP Forrest M. Mims 111 . 3 0 R >> /Font << /F1.0 7 0 R /F17.0 8 0 R /F3.0 9 0 R /F4.0 10 0 R • NPN and PNP transistors function in essentially the same way. The Excel Functions covered here are: VLOOKUP, INDEX, MATCH, RANK, AVERAGE, SMALL, LARGE, LOOKUP, ROUND, COUNTIFS, … The relation between α and β is given by, β = α / (1- α) and α = β/ (β+1) The collector current in PNP transistor is given by, IC = – α IE + ICBO where ICBO is the saturation current. For the pnp device, reverse the directions of all current labels and reverse the order of subscripts involving node labels, i.e. Example) The PMOS transistor has V T = -1 V, Kp = 8 µA/V2, W/L = 25, λ = 0. It is sometimes useful to use some simple transistor theory to derive the gain calculations and formulas. %PDF-1.5 %���� The following figure shows how different practical transistors look like. << /Type /Page /Parent 5 0 R /Resources 6 0 R /Contents 2 0 R /MediaBox The balance of the circuit with the transistor and collector and emitter resistors. I D will be constant. o 40293 10895 PRINTED IN U.S.A. A Division of Tandy Corporation Fort Worth, TX 76102 Rad.e 'haek . The GAIN is simply the amount of amplification. These back to back PN … 1265 0 obj <> endobj `�+�Z~[Q��YU=�-����(X�\{(@�l)0_x��+;3�c~�jK��eq�'7�e�r�,IfQ�N|i��5Bc)��q�'B�z��d���-{�Ң�]v���3Ek�(,p�r{����nil2,��Y��B�����/b.K��E�lF`K��l�z���ȵ@�� q�tNi�l�M �� Without this base current, the transistor can't turn on. This, together with the many other advantages of MOS transistors, has made the JFET virtually obsolete. The model of Equation (3) and the corresponding equations are valid for both PNP and NPN transistors and are independent of the load impedance of the method of biasing. Energy Band diagram of solids 2. tutorials we saw that simple diodes are made up from two pieces of semiconductor material, either silicon or germanium to form a simple PN-junction and we also learnt about their properties and characteristics. How to Calculate the Base Current, I B, of a Transistor. We have so far discussed the constructional details of a transistor, but to understand the operation of a transistor, first we need to know about the biasing. 2 0 obj Why Do We Need Transistors? 6 0 obj The reason: bipolar transistors are the mainstay of interface elements to microcontrollers. Thus, the circuit is stable in this configuration. << /ProcSet [ /PDF /Text /ImageB /ImageC /ImageI ] /ColorSpace << /Cs1 157 /ColorSpace 27 0 R /Decode [ 1 0 ] /BitsPerComponent 1 /Filter The NPN transistor consists of two n-type semiconductor materials and they are separated by a thin layer of p-type semiconductor. It is configured in two ways as NPN and PNP. Transistors: Bipolar Junction Transistors (BJT) General configuration and definitions The transistor is the main building block “element” of electronics. /FlateDecode >> In fact, the state of the system can be flipped. Bipolar transistors are essentially two diodes placed back to back. These back to back PN … 1. Transistors: Bipolar Junction Transistors (BJT) General configuration and definitions The transistor is the main building block “element” of electronics. I … Note: Simpson (page 227) writes an equivalent formula for the gain using the transistor parameter b and a slightly different temperature, T = 3000K. endobj h�b```��,�A cb�/��ln���&����a�c�_JP���Ux�YX/�Y���G����'EE���\<=�>V]�RjYb�-xt#��l؟�͐Ng�U�PR^�V��Z^V��^ښ� ��q���ĉ���F������|�s�x۳���Y:���9��a����r�H행�1`EF�@�9��{���q�M�6��b�Uo��zح'��q��ýe)��m:���*θn�pMd�EGGcG�G���h`�h`� a� Figure 3 gives the h-parameter models for the transistor in CB and CC configurations. Transistor Biasing. transistor beta, change. ��]D1im�̓���,] �>0��+������� ���/�������Łf�㼋V�?��N)ݾ�&�=�t��5O��EzДu�3�:�� ��'��L������$�q&�{NFυ��ٰp2ef�d������ ��E��̀/�����}S��η.��iJ���N :���5�0����"e:0<1X���wDU��j[h���Ic��?�e���\=g��7�Rr�R�b�,�d�a �>�&�����Z�z}~L:{���n�c�)`~D��D��ʵ�za���T����@�z`�K|����I�J�NB�*����q�PI�퉝aT�Ъ�r�v�~� Note:This circuit was designed when we were just learning how to teach transistor function. The simplest biasing applies a base-bias resistor between the base and a base battery VBB. In terms of the hybrid parameter model (we will see this model soon) rBE = hie / hfe Using rBE to design a circuit is a dangerous practice as it depends on temperature and varies )z��$H��~��e��+w�LF�NF�`5�炚�A�i�@���� �gll+�F��B� gR� �.k��������g &f�1cYj!f@��3捜/�+]�A"n *�) �,�Cɂ�7̡�l!N���6����U�$Bn摵:����E���v�S��׻�g�����6�> While Unipolar transistor i.e. Learn Field-Effect Transistors (AC Analysis) equations and know the formulas for FET Transconductance Factor, JFET or D-MOSFET, E-MOSFET and JFET. VOLTAGE DIVIDER BIAS CIRCUIT Provides good Q-point stability with a single polarity supply voltage This is the biasing circuit wherein, ICQ and VCEQ are almost independent of beta. Diode. An example of an audio amplifier stage using base-biasing is “Crystal radio with one transistor . endstream endobj startxref TRANSISTOR (JFET) The junction field-effect transistor, or JFET, is perhaps the simplest transistor available. As we know that a transistor is a combination of two diodes, we have two junctions here. Tutorials. Bipolar transistors come in two basic types: npn and pnp. 2599 Georgia Tech ECE 3040 - Dr. Alan Doolittle Further Model Simplifications (useful for circuit analysis) T EB T EB T CB T EB V V R C S V V C F F V V R V V C F F +⇒=I e − − 0 0α 0 1 0 Ebers-Moll Forward Active Mode Neglect Small Terms . Toggle Nav. An NPN transistor is the most commonly used bipolar junction transistor, and is constructed by sandwiching a P-type semiconductor between two N-type semiconductors.An NPN transistor has three terminals– a collector, emitter and base. V CE is approximately equal to VCC – When the base-emitter junction is forward-biased and there is enough base current to produce a maximum collector current, the transistor is saturated. In the PNP transistor these polarities are reversed: the emitter and collector are P -Type material and the base is N -Type material. 1304 0 obj <>stream 1284 0 obj <>/Filter/FlateDecode/ID[<2DF1610E31597C4998FA31107C168C7B>]/Index[1265 40]/Info 1264 0 R/Length 94/Prev 510961/Root 1266 0 R/Size 1305/Type/XRef/W[1 2 1]>>stream Bipolar junction transistor (BJT) is a bidirectional device that uses both electrons and holes as charge carriers. NJFET PMOS Depletion. Sometimes you see them, but more-often-than-not they're hidden deep within the die of an integrated circuit.In this tutorial we'll introduce you to the basics of the most common transistor around: the bi-polar junction transistor (BJT). In fact, the amplifier increases the strength of a weak signal by transferring the energy from the applied DC source to the weak input ac signal The analysis or design of any electronic amplifier therefore has two components: A bipolar junction transistor, shortly termed as BJT is a current controlled device that consists of two PN junction for its function. /Im1 25 0 R >> >> Transistors make our electronics world go 'round. Thus you will be seeing a lot of BJTs when you work with sensor interfaces. Example) The PMOS transistor has V T = -1 V, Kp = 8 µA/V2, W/L = 25, λ = 0. 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. Basic transistor … Suppose that you have a FM receiver which grabs the signal you want. Among the two, NPN transistor is the most preferred for the sake of convenience. When more than one equation is given, either can be used. 3. �27�{�#��W�� El término «transistor» es la contracción en inglés de transfer resistor («resistor de transferencia»). How to Calculate α (alpha) of a Transistor. A Transistor is a three terminal semiconductor device that regulates current or voltage flow and acts as a switch or gate for signals. . ��� It has some important characteristics, notably a very high input resistance. devices like diode and transistor) on a small single block (or chip) of a semiconductor has revolutionized the electronics technology. El transistor es un dispositivo electrónico semiconductor utilizado para entregar una señal de salida en respuesta a una señal de entrada. An NPN transistor is the most commonly used bipolar junction transistor, and is constructed by sandwiching a P-type semiconductor between two N-type semiconductors.An NPN transistor has three terminals– a collector, emitter and base. PMOS Enhance. the mathematical formulas are kept as simple as possible and as less as possible. This article will mainly introduce what exactly a transistor is and its detailed characteristics and functions. /F13.0 21 0 R /F2.0 22 0 R /F9.0 23 0 R /F7.0 24 0 R >> /XObject << It has some important characteristics, notably a very high input resistance. %%EOF 1st Way to Calculate Alpha α If the β of the transistor is known, α can be calculated very easily by the formula: �Jd��:�`F�$T�7�݁���ٗќ_'��ڙ���7����P��AJ��KdDs�&����#��쒯���$��(�9ݞ��q?C!�4��*P�D��YiҚ�q�3;S�S�����n�z�|����ʜ��T���@R����1�'E�Y�9�-�s����{5;�� ]���e��������c�0�~\u�����4�;7s �u�m3ɠ����"~�@��|Tj�]��}P����e����T�]���2���D�\�4Q�(�jȰc=?fgr�8qR���b�c4�,�4e����F4M����\������q�&@�~�:b0Q[�捋J�bڜ��ς߻� Wiser now, we know there are some errors below in the math with the filter calculations. Learn more about BJT working and construction here What is a NPN Transistor. stream Note: Simpson (page 227) writes an equivalent formula for the gain using the transistor parameter b and a slightly different temperature, T = 3000K. Excel Formulas PDF is a list of most useful or extensively used excel formulas in day to day working life with Excel. For I = 100 µA, find the V SD and V SG for R = 0, 10k, 30k, 100k. ����r2Fp���)�W3��\�����0;9�Fݡ-�ht�25f�R�u�s��i�k�Vz*�s\�Ɔ��7�1ָ��=��JF.�}��bcV��H�`�����"օ�g��z���'�(!a�A����/�>%��;ɗ���|�Ԓ��uK��jKdha cR���4VM.��sM���:������W�}�����c�w=����șP,m��4�12U>�S����N��4;4X ” crystal radio, Ch 9. If the formula gives 41k resistor, then you must use a lower value resistor for the relay driver transistors base, may be a 33 K will be fine. I B = I C /β = (4*10-3)/100 =40uA. Transistor is a kind of solid semiconductor device, which has many functions, such as detecting, rectifying, amplifying, switching, voltage stabilizing, signal modulating and … endobj Transistor Symbols. Current gain = Collector current/ Emitter current (In common base transistor) α = IC/IE. • 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 formulas and example questions are set out below: A simple way of remembering the formula is seen in the diagram opposite OR you can learn each of the formulas below. Among the two, NPN transistor is the most preferred for the sake of convenience. endstream What is a NPN Transistor. Calculate the base current of a bipolar NPN transistor having the bias voltage 10V and the input base resistance of 200kΩ. endobj Bipolar transistors have 3 leads: 1. endobj Thus, in its most basic form, a transistor is a current amplifier. 2. Pass transistors require lower switching energy to charge up a node, due to the reduces voltage swing. The GAIN is simply the amount of amplification. NPN Transistor Examples. Energy Band Diagrams of Metals, Semiconductors & Insulators CHAPTER FORMULAS & NOTES 2 - Solution λ = 0 (no channel length modulation) ! Tutorials. endstream endobj 1266 0 obj <. /F16.0 11 0 R /F12.0 12 0 R /F10.0 13 0 R /F11.0 14 0 R /F8.0 15 0 R The received signal will obviously be weak due to the disturbances it would face during its journey. Unfortunately, however (for the JFET), the MOSFET has an even higher input resistance. This may seem like a silly thing to do but the diodes are not the same. – A transistor is in cutoff when the base -emitter junction is not forward-biased. There are two basic types of bipolar transistor construction, PNP and NPN, which basically describes the physical arrangement of the P-type and N-type semiconductor materials from which they are made. 9��]pVm��XVE�����m�\�H�¢����r����͐`G�8H��� _����9}��-�M�����@�h�"�v�S���e���J#Ս3�x��-1+�W �}2y�2�Y�������(����x����Srv�R�f$��q�X��e0r���e��׎��s�1�)�Vg�ǩ5������:U�t�J���m��v̷�a��.�y�A,>�x��4.���cLR�s�I�t�皙L0��I�ywC�%�4�J�xɡ�E������\d(n�qӡ�%��&$��#�J�����^�B��SX���R�ɋ dh�%35{���EvI����3�v);�2 � �@�����ODjh����&���K1�����2�tb�p�=��ːgc�HG2�r��r-��$��a�m]-�gD"A�1Q)7,($KD��[����^υ2���ִڎs�K\�1[;mwn��e'�; x�Dڊ�@b�Z���!ߎe�B�Iݝ�b�*�{=�\qzXe�O8�r��^,�mx%ȃ/�X��c�B����:e�#}^��j�w! TOP Diagrams & Circuit Diagrams 1. The most widely used circuit is the common emitter where the emitter is common to both input and output circuits. Unfortunately, however (for the JFET), the MOSFET has an even higher input resistance. The analysis or design of a transistor amplifier requires knowledge of both the dc and ac response of the system. If a signal is applied in the right place, the circuit will flip. Transistors are used to amplify current and so in an examination you could be asked to find the BASE current or COLLECTOR current or the GAIN. BJT is also used as a switch and as an amplifier. It is a semiconductor device and it comes in two general types: the Bipolar Junction Transistor (BJT) and the Field Effect Transistor (FET). For the pnp device, reverse the directions of all current labels and reverse the order of subscripts involving node labels, i.e. Use the following formula to determine the A-C Current Gain. PJFET NMOS Enhance. V V I RR. The procedure to follow for the analysis of any amplifier circuit is as follows: 1. MOS Transistor Qualitative Description Inversion case, V GS > V T(continued): If L<V sat. MOS Transistor I-V Derivation With our expression relating the Gate voltage to the surface potential and the fact that S =2 F we can determine the value of the threshold voltage is the oxide capacitance per unit area where, 2 (for p -channel devices) 2 2 2 (for n -channel devices) 2 2 ox ox ox F S D ox S T F F S A ox S T F x C qN C V qN C V There are many ways to mix these together, which is an art (Steve Jobsoften called laying out circuits "digital … 7 Electrical conductivity of a Semiconductor. An NPN (Negative-Positive-Negative) type and a PNP (Positive-Negative-Positive) type. Notes on BJT and transistor circuits (Based on Dr Holmes’ notes for EE1/ISE1 course) 10 Bias Stabilisation - 1 • Biasing at constant VBE is a bad idea, because IS and VT both vary with temperature, and we require constant IC (or IE) for stable operation. Learn Bipolar Junction Transistors (DC Analysis) equations and know the formulas for the Bipolar Transistor Configurations such as Fixed-Bias Configuration, Emitter-Bias Configuration, Collector Feedback Configuration, Emitter Follower Configuration. It is a semiconductor device and it comes in two general types: the Bipolar Junction Transistor (BJT) and the Field Effect Transistor (FET). 2N3553 transistor in a TO39 metal can Transistor gain derivation. The NPN transistor has an emitter and collector of N -Type semiconductor material and the base material is P -Type semiconductor material. Bipolar junction transistor is defined as the device that has a three-terminal semiconductor which is used as a current controlling device. Toggle Nav. You have the transistor in your hand. /F14.0 16 0 R /F5.0 17 0 R /F5.1 18 0 R /F6.0 19 0 R /F15.0 20 0 R It is sometimes useful to use some simple transistor theory to derive the gain calculations and formulas. Introduction. In order to build an amplifier, all you need are a transistor, a power source, some resistors, and some capacitors. 4 0 obj Common Collector Transistor Configuration (CC) The common collector transistor configuration is also known as the emitter follower because the emitter voltage of this transistor follows the base terminal of the transistor. o 40293 10895 PRINTED IN U.S.A. A Division of Tandy Corporation Fort Worth, TX 76102 Rad.e 'haek . Now you will put that knowledge to use. VCE becomes VEC . When current flows through one diode it provides carriers to carry current through the other part of the element. Calculate the base current IB to switch a resistive load of 4mA of a Bipolar NPN transistor which having the current gain (β) value 100. ( 1) CC BE c BE. 2… Here you will use your transistor to amplify some spikes. VCE becomes VEC . For I = 100 µA, find the V SD and V SG for R = 0, 10k, 30k, 100k. The Transistor is a semiconductor device provided with three terminals called base, emitter and collector. Bipolar Transistor Basics In the . %��������� A similar circuit is shown in the figure below. You stare at it, knowing the power it contains and what it has done for the world. You can now explain with confidence what p-doping, n-doping, and depletion layers mean. The following formula is used to calculate the current gain of the CE (α) when the CB value is given i.e (β). Here the majority charge carriers are the electrons. The NPN transistor behaves like two PN junctions diodes connected back to back.. 1602 LCD (1) 74HC595 (1) ADC (1) Algebra (1) Analog-to-Digital Converter (1) Arduino (1) Browse All Tags; Basic Electronics A PNP transistor is a semiconductor device with three distinct areas: an n-region sandwiched between two p-regions. The base current, IB, of a transistor is a crucial current of a bipolar junction transistor. There are several ways to find the base current, IB, of a transistor. Figure 3 gives the h-parameter models for the transistor in CB and CC configurations. field effect transistor uses only one type of charge carrier. junction field-effect transistor, or JFET, is perhaps the simplest transistor available. ... been discussing are for the transistor itself, not the amplifier circuit. CC BE c B. V V I R. β − = Note:it seems that beta in numerator canceled with beta in denominator . Common Emitter Amplifier Circuit The common emitter amplifier circuit is the most often used transistor amplifier configuration. Learn Bipolar Junction Transistors (DC Analysis) equations and know the formulas for the Bipolar Transistor Configurations such as Fixed-Bias Configuration, Emitter-Bias Configuration, Collector Feedback Configuration, Emitter Follower Configuration. When more than one equation is given, either can be used. The NPN transistor behaves like two PN junctions diodes connected back to back.. 25 0 obj stream ����FGHP��=@B`&H�������b pY0�3-� >C�@���GL �\[$~�-tI`o�K��=ü��@��&qW�EH��f`/�� �vΧ@z/{} ��d`�����p �'�O�� ����K�H�u+V��v#�f�ָb�+�>@�/;�nv65 �� eo��͢|����*�i�i��b�x�o����� fM�.����Е�_ێ�ٞt,_@�W��������kO�׼Q��<5Mz�sVr9� �H�i�֚.��R�d�݂� �N�¬��E��pZ4Yk�Џ&���p�y�N�h�[��9Pw�;@�x!�N�� Gmm���"�1z힄.��y��aHc�����!�H%*����lWV������F����C�ٱү};�:c�e�� F&�g�ʿ�m�Hؙ*l7������yjT��0{� T{Xg�U�a[�1�ټ �ڃ����Ý��;��M����w�� ����tʁ�~�U��$@? Nevertheless, since no circuit analysis can be achieved without mathematics, the reader may have to go through some-hopefully- simple and short calculations. If L~L, the voltage dropped across the the channel (V SAT) varies greatly with V DS due to large modulations in the electric field across the pinched off region ( E=[V DS-V SAT]/[ L]). These symbols can be represented inside a circle. [ 0 0 612 792 ] >> CHAPTER FORMULAS & NOTES Formulae For SEMICONDUCTORS. Discuss transistor models List and define the r parameters Describe the r-parameter transistor model Determine r9e using a formula Compare ac beta and dc beta List and define the h parameters r Parameters The r parameters that are commonly used for BJTs are … This Blog will give you the Excel formulas PDF/list of the Key Functions of Excel. %PDF-1.3 But the circuit shown above is symmetric, so either the right-hand light or the left-hand light can be "on." << /Length 1 0 R /Filter /FlateDecode >> Title: Engineer's Mini-Notebook - Formulas, tables and Basic Circuits Author: X Subject: Electronics transistor to turn on, as we assumed in the first place. NPN transistor is one of the Bipolar Junction Transistor (BJT) types. - Solution λ = 0 (no channel length modulation) ! The flowing of these electrons from emitter to collector forms the current flow in the transistor. 0 Such a circuit is known as Integrated Circuit (IC). We will redesign this circuit when time and resources permit, but note that the circuit still works (can amplify spikes). x���n�@��8V�,l�] H*$�]{:���U*kv��8� D/���;�t����� sK�ۙC�4e�ۙo~��\| ��哄GlAJڜ�:���E���4I"x;���H̟�/�.W"��F8�"=�A���Q"(x���2Wn�:�}YDZ֍�^�&x��x��#�r��I�&����CC��b��Hq�F�����?G=4�}� ����ga���>�6?���}����Ӄ�q���x���E�L=�ă ����}�#�("�%9��. ECE 3050 Analog Electronics - BJT Formula Summary Equations are for the npn BJT. 2N3553 transistor in a TO39 metal can Transistor gain derivation. The model of Equation (3) and the corresponding equations are valid for both PNP and NPN transistors and are independent of the load impedance of the method of biasing. Introduction. α (Alpha), the factor by which emitter current is multiplied to yield collector current, can be calculated in two ways.