lab experiment number 8 common base amplifier, Summaries of Electronics

Download lab experiment number 8 common base amplifier and more Summaries Electronics in PDF only on Docsity! Department of Electrical Engineering Faculty Member: ______Saqib Nazir____ Dated: ___20-10-19___ Semester:___3rd__________ Section: _____B________ EE215: ELECTRONIC DEVICES AND CIRCUITS Lab 8: BJT I-V characteristics and Type Identification PLO4 PLO5 PLO8 PLO9 Name Reg. No Viva / Quiz / Lab Performan ce Analysis of data in Lab Report Modern Tool Usage Ethics and Safety Individual and Team Work 5 Marks 5 Marks 5 Marks 5 Marks 5 Marks Maryam Mahmood 257913 Iram Fatima Aulakh 249796 Sahar Zahid 257831 LABORATORY EXERCISE-8 BJT I-V Characteristics and type identification EE215: Electronic Devices and CircuitsPage 1 Objective: To study current-voltage characteristics of BJTs • The primary purpose of this lab is to develop a working knowledge of Bipolar Junction Transistor (BJT). Transistors are current controlled devices which find applications in a vast array of circuits including but not limited to amplifiers, electronic switches, multipliers etc. • First, the students will learn the method that is used to determine the type of the transistor and find out and label various terminals of the BJT. • Second parts deals with the study the I-V characteristics of the BJT, and see how varying the parameters of the BJT affect them. For our implementation and simulation phase the 2N2222A transistor will be used which is one of the popular type of BJT around. Required Resources The following components, test equipment and software would be required. • 2N2222A Transistor • DMM • Oscilloscope • Resistors • Capacitors • Power Supply • PSpice Simulation Software. The Experiment The experiment is broken down in two exercises; one of the experiment is divided into two parts namely:simulation and implementation. You are required to observe and record the simulation/ implementation results and answer the given questions. Include your answers in your lab reports. Exercise 1: BJT Type Identification (Implementation-I) In this part of the experiment you will be given a sample transistor and using the procedure below you are required to determine whether the transistor is an NPN or PNP transistor. You are also required to identify the terminals of the transistor. Procedure • Set your digital multi-meter to diode check mode. EE215: Electronic Devices and CircuitsPage 2 • The test circuit in figure 2A is used to determine the dependence of the collector current on the base-emitter voltage as well as the voltage applied at the collector. The source VBB in figure 2A controls the amount of base-emitter voltage and the current that enters the base terminal and the source VCC controls the voltage that appears at the collector terminal. • In the first simulation run, set the value of R1 = 1Ω. • Create an appropriate simulation profile and perform DC Sweep Analysis. • In the Primary Sweep tab, specify the voltage source as VCC. Vary it from 0 to 30 V. EE215: Electronic Devices and CircuitsPage 5 • Check the option for Secondary Sweep and specify the voltage source as VBB. Vary it from 0.4 to 0.7 V in steps of 0.05 V. EE215: Electronic Devices and CircuitsPage 6 • Run the simulation and make use of axis variables and traces to get a graph between the collector current and. (Hint: The emitter is grounded so is effectively equal to VC). • Use Axis Setting Option to get different views of the V-I curve. Select different settings and save the graphs that depict the BJT graphs which are easily readable. R1 = 1 KΩ EE215: Electronic Devices and CircuitsPage 7 VBB iB 0.7 14.585 uA 0.6 5.228 uA 0.5 1.2714 uA 0.4 258.35 nA • Calculate the average value of β for each value of base current. Comment on and explain the trend that you observe. IC (0.4 V) IC (0.5 V) IC (0.6 V) IC (0.7 V) VBB iB ic β 0.4 258.35 nA 27.2 uA 105.28 0.5 1.2714 uA 172.238 uA 135.3 0.6 5.228 uA 846.833 uA 162.1 0.7 14.585 uA 2.616 mA 179.4 • On the IC versus VCE plot, identify each region of operation of the transistor. EE215: Electronic Devices and CircuitsPage 10 Saturated region Active regionCu -off region • Why does the graph of the collector current have a considerable slope in the active region of the transistor? Explain. Because of Early Effect, as VCE increases, ic also increases. This is known as early effect which is responsible for the slope in the graph. • Calculate the Early voltage of the transistor using the plot that you have obtained. x1 = 9.507 V x2 = 14.335 V y1 = 2.6004 mA y2 = 2.7500 mA m = = 0.031 So; y = mx +c y = 0.031*x + c c = 2.3 EE215: Electronic Devices and CircuitsPage 11 For VA, putting y = 0; 0 = 0.031* VA + 2.3 VA = = -74.19 V • Now open the PSpice model (Right click on the part and select PSpice Model) of the transistor and compare the calculated value of Early voltage with the one specified in the model. Are they the same? They are almost same. The Pspice model Voltage is 74.03, while calculated is 74.19, which are nearly equal. • Try modifying the value of the Early Voltage specified in the PSpice Model and run the simulation again. Is there any effect on the I-V characteristics? On increasing Early Voltage, the graph of IC vs VCE has smaller slope, and hence a greater . • Try modifying the value of the forward saturation current Is and run the simulation again. Do you expect any change in the characteristics? Is the plot according to your expectations? On increasing the value of IS, the graphs of IC vs VCE shift upwards as values of IC increases. This is as expected since IC=, which implies that IC is directly proportional to IS. CAUTION: - Be sure to reset any changes you make in the SPICE models of the parts or your subsequent simulations will be affected. Exercise 2 Part B: Common Emitter I-V Characteristics of the BJT (Implementation-II) This exercise involves the implementation of a circuit to test the I-V characteristic of a BJT which you have extensively studied through the simulation phase of the experiment. • Patch the circuit as shown in figure 2B. EE215: Electronic Devices and CircuitsPage 12