ELECTRONICS AND SEMICONDUCTOR ENGINEERING

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1 TALLINN UNIVERSITY OF TECHNOLOGY Department of Electrical Drives and Power Electronics Tanel Jalakas, Valery Vodovozov, Dmitri Vinnikov ELECTRONICS AND SEMICONDUCTOR ENGINEERING Laboratory works Tallinn 2008

2 Tanel Jalakas, Valery Vodovozov, Dmitri Vinnikov. Electronics and Semiconductor Engineering. Laboratory works Tallinn University of Technology Department of Electrical Drives and Power Electronics Tallinn, 2008 Preparation and publication of this study material was supported by SA Innove Tallinn University of Technology Department of Electrical Drives and Power Electronics Ehitajate tee 5, Tallinn Telefon Fax Cover designed by Ann Gornischeff Copyright: Tanel Jalakas, Valery Vodovozov, Dmitri Vinnikov, Tallinn University of Technology, Department of Electrical Drives and Power Electronics, 2008 ISBN

3 Contents 1. Introduction Power electronics laboratory internal and safety regulations Safety arrangements Implementation of the laboratory task Preparation of the report Report submission and defence of the tasks Measuring devices Laboratory works Work no. 1. Semiconductor diode Work no. 2. SCR-thyristor Work no. 3. BJT-transistor in common emitter connection Work no. 4. Single-phase ridge rectifier Work no. 5. Operational amplifier

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5 1. Introduction These regulations are intended for use as a tutorial aid by the implementation of laboratory tasks in the framework of the course AAR3320 Electronics and Semiconductor Engineering. The laboratory of the power electronics is located in the Power Engineering Building, Mustamäe, Ehitajate tee 5, room VII-101. The course of electronics and semiconductor engineering provides theoretical knowledge about signals, amplification and filtering, passive and active components, thus also about, semiconductor components diodes, transistors, and thyristors. By drafting of the regulations it was assumed that the students have derived relevant theoretical knowledge from lectures and manuals. These instructions contain three laboratory tasks on different semiconductor devices (diode, thyristor, transistor), one laboratory task to determine the main parameters and characteristics of a single phase bridge rectifier, and another- to study working principles of an operational amplifier. Experimental diagrams are given in the instructions. Student pass in the course of electronics and semiconductor engineering requires that the student has performed required experiments for each task, has prepared proper reports and has successfully defended the task. 5

6 2. Power electronics laboratory internal and safety regulations 2.1 Safety arrangements The connection must be composed to enable free access to the feeder board, experiment stand, emergency switch and test devices, which are adjusted in the run of the experiment. Measurement devices and appliances should be in the right stand and their scales well visible. Long-hanging conductor entanglement could lead to a possibility of getting an electric shock; displacement of the devices or pulling them down from the table, should be avoided. Sticking the conductors wilfully is prohibited. Measurement devices, the frames of which are connected electrically (oscilloscopes, electronic voltmeters etc.) must be connected to the earthed terminal of the mains. While taking oscillograms in AC circuits the galvanic isolation is to be provided positively, using a separating transformer or the differential end piece of the oscilloscope. The circuit could be switched on upon permission of the instructor, preliminarily warning the members of the working group. Changes in the circuit could be made only when the voltage is switched off. In live only the measurement range of the voltmeter could be changed and the measurement conductors of the voltmeter and oscilloscope be replaced. Thereby special caution must be applied by dangerous voltages (over 50 V). While working with electrical machines precautions must be taken to ensure that rotating machines do not grip clothes, hair or hanging conductors. Before starting the machine the members of he working group must be warned. If the device is functioning improperly (overheating, goes smelly, sparkles or electric arc appears between contacts), the device must be switched off immediately. In the case of an accident the sufferer must be set free of voltage, using the safety switch, placed at each working table. Thereafter the rescue service must be informed and first aid provided before the arrival of the rescue service. It is prohibited to touch non-isolated live parts; connect conductors in the live circuit; switch loaded circuits by switches of open construction; switch the main board switches without supervisor s instruction; lean and sit on the electrical devices, hang clothes on them, place bags, cases etc. on the working place; leave the laboratory for a longer time without supervisor s permission; touch other devices not needed for the given task; implement the experiment alone; eat, drink and smoke in the laboratory. 6

7 2.2 Implementation of the laboratory task The tutorial process consists of the preparation of the laboratory task; implementation of the required tests, preparation of the report and its defence. A working group may be composed of four students as a maximum. The students shall be engaged in the study in the power electronics laboratory and all activities interfering with it are prohibited Authorization to the laboratory task is provided to the student who: is aware of the given safety and internal regulations and has verified that with his/her signature on the checklist; is familiar with the feeder circuits of the laboratory; is prepared for the task, i.e. has carefully read the description of the laboratory task, drawn up the required experimental diagram, calculated the required values, prepared the tables and is able to answer checking questions; has submitted the report of the previous task. First the student will compose the required circuit. At the start, measurement devices shall be placed properly, instruments must be placed on the table so, that all scales are well visible. If possible, the order of the principal electrical diagram should be followed in circuit element placement. The device regulating the main voltage of the circuit and measuring voltmeter should be placed side-by-side, thus making it easy to follow voltmeter s readings while regulating the voltage. When the experimental circuit is being composed, circuits indicated by bold lines on the diagrams are connected first. Next the voltage and control circuits represented by thin lines are connected. It is always possible to compose the switching circuit so that there will not be more than two-three conductor ends connected to less than one terminal or socket. Before switching on the voltage, control whether arms of all measurement devices are on zero or not, and whether the measuring ranges correspond to the expected values of the variables to be measured. If required, the readings are corrected by means of correctors and proper measurement ranges will be selected. At the beginning of the first experiment, the circuit may be switched on only upon supervisors acceptance. At the end of the experiment the students shall: submit the notebook of the laboratory tasks to the supervisor to verify results of the experiments; after permission of the supervisor, take off the circuits, place instruments and measurement devices onto their permanent places and set the workspace in order. The experiments are considered as completed if the supervisor has verified the results and has given permission to terminate the laboratory work. 7

8 2.3 Preparation of the report The report shall consist of a title page, the legend and tables, and a graphical part. On top of the title page the formal header is located (Fig.1). The connection diagram is drawn under this header. If there are several circuits, then they could be presented on the following pages and supplied with corresponding captures. The requirements for the preparation of the legend, formulas, tables and graphics are provided in the instructions Preparation of student graduation papers, accessible in the Internet on the page You have to click õppetöö ja lõpetamine. Tallinn University of Technology Department of Electrical Drives and Power Electronics Student: Group: Task implemented (date) Report submitted (date) AAR3320 Electronics and Semiconductor Engineering Task no. (Title of the task) Objects of the experiment Devices used Figure 1. Header of the title page The final part of the report is an abstract. The abstract must contain a critical analysis and evaluation of the results. Therefore compliance of the results with theoretical aspects, data of the experiments object and valid standards are compared and appropriateness of the measurement methods and measuring devices is evaluated. Special attention must be paid to the differences of the experimental and theoretical results, errors of experiments, incorrect measurement readings and their reasons. It is helpful to study over the questions given at the end of the task, to be well equipped for the defence of the task. 2.4 Report submission and defence of the tasks The student shall prepare a report on the task accomplished, according to the requirements of the instructions. The report must be submitted before the following task. If the report is not submitted or it is inadequate the supervisor has the right remove the student from the next laboratory task. Defence of each laboratory task involves answering the questions to assess the preparation of the student for the laboratory task, practical knowledge shown in the laboratory and activity in solving the problems that arose as well as the evaluation of the content and organization of the report. 8

9 3. Measuring devices In the laboratory tasks the following measuring devices are used: Lutron DV-101 DC voltmeter, Lutron DA 137 DC ampermeter, Lutron AV 102 AC voltmeter. When using digital measuring devices in the laboratory take the following precautions: Be sure that the laboratory wires are in the right sockets, according to the needed measuring range and the polarity is right (Fig 2 sockets 3 5). Use switch 6 to select the measuring range. Switch the measuring device on with switch 2 and take the needed measurements. Figure 2. Educational DC ampermeter A) and DC voltmeter B) In Fig. 2. all the important elements of digital laboratory measuring devices are listed. These are as follows: 1 LCD display, 2 supply, 3 ampermeters (max 250 ma positive signal), voltmeters (positive signal), 4 ground connection, 5 ampermeters (max 5 A positive signal). 9

10 6 selection of the measuring range. Ampermeters (2 ma 5 A) and voltmeters (200 mv 200 V). When you finish your work, please switch the measuring devices off, using switch 2. Absolute maximum ratings for the measuring devices are: maximum input voltage for the DC voltmeter 250 V, maximum input voltage for the AC voltmeter 600 V, maximum input current for the DC ampermeter 5 A (NB! be careful when regulating current with the rheostat). The accuracy of the measuring devices is 1,5%. 10

11 4. Laboratory works 4.1 Work no. 1. Semiconductor diode Objective To determine the characteristics and the main parameters of the semiconductor diode. To develop awareness of the application possibilities of different types of semiconductor diodes. Test devices different diodes D, DC voltmeter V, DC ammeter and microammeter A, potentiometer R k, connection wires. Test circuit Figure 3. Diode characteristics Procedure 1) Study the test devices, write down the types and the technical data of the diodes and measuring instruments (type, accuracy class etc). 2) Select the potentiometer and measuring instruments according to the parameters of the diode. 3) Compile the test circuit of the forward biased diode (Fig. 3). 4) Turn the voltage divider (potentiometer R v ) until the input voltage U in = 0. 5) Take up the voltage-current characteristic U F = f(i F ) of the forward biased diode and for that purpose: change the value of the input voltage with a suitable step by the help of the potentiometer R v until the maximum forward current of 11

12 the diode is achieved. Sign up the values of the forward voltage U F and the forward current I F of the diode (6 8 measurements); write the results into the table; at the end of the experiments, regulate the voltage divider until the input voltage U in = 0. 6) Put together the test circuit of the reverse biased diode. 7) Take up the voltage-current characteristic U R = f(i R ) of reverse biased diode and for that purpose: change the value of the input voltage with a suitable step by the help of the potentiometer R v until the breakdown voltage of the diode is achieved. Sign up the values of the reverse voltage U R and the reverse current I R of the diode (6 8 measurements); organize the results into a table; at the end of experiments, turn the voltage divider until the input voltage U in = 0. Analysis of observations 1) On the basis of the results draw the voltage-current characteristics of the forward biased and the reverse biased diode. 2) Calculate the resistances of the forward biased and the reverse biased diode for each measurement. 3) Calculate the power losses of the forward biased and the reverse biased diode. 4) Conclusions. 12

13 4.2 Work no. 2. SCR-thyristor Objective To determine the characteristics and the main parameters of the SCRthyristor. To develop awareness of the application possibilities of the different types of SCR-thyristors. Test devices Test circuit different thyristors D, DC-voltmeter V, DC-milliammeter A1, DC-ammeter A2, potentiometers R v, R j, resistors R 1, R 2, connection wires. Figure 4. SCR thyristor Procedure 1) Study the test devices, write down the types and the technical data of the thyristors and measuring instruments (type, accuracy class etc). 2) Select the potentiometers, resistors and measuring instruments according to the parameters of the thyristor. 3) Compile the test circuit of the forward biased thyristor (Fig. 4). 4) Turn the voltage divider (potentiometer R v ) until the input voltage U in = 0. 5) Take up the voltage-current characteristic U F = f(i F ) of forward biased thyristor when the gate current (control current) I G = 0, and for that purpose: 13

14 change the value of the input voltage with a suitable step by the help of the potentiometer R v until the maximum forward voltage of the thyristor is achieved. Sign up the values of the forward voltage U F and the leakage current I L of the closed thyristor (6 8 measurements). Make sure that the thyristor is turned off; sign the results into table; compose the circuit of the reverse biased thyristor and change the value of the input voltage with a suitable step by the help of the potentiometer R v until the breakdown voltage of the thyristor is achieved. Sign up the values of the reverse voltage U R and the reverse current I R of the thyristor (6 8 measurements); organize the results into table; in the end of experiments, screw the voltage divider until the input voltage U in = 0, 6) Turn on the thyristor and for that purpose: By the help of the potentiometer R v adjust determined forward voltage of the thyristor U F ; increase the control voltage by the help of the potentiometer R j until the thyristor turns on; sign up the forward current I F, forward voltage U F and the control current I G of the thyristor; increase the input voltage U in with suitable step and measure the forward current I F until the maximum forward current of this thyristor is achieved (6 8 measurements); organize the results into a table; at the end of the experiments, screw the voltage divider until the input voltage U in = 0. Analysis of observations 1) On the basis of the results draw the voltage-current characteristics of the forward biased and the reverse biased thyristor. 2) Calculate the resistances of the forward biased turn on state and turn off state thyristor and the reverse biased thyristor. 3) Conclusions. 14

15 4.3 Work no. 3. BJT-transistor in common emitter connection Objective To determine the input and output characteristics and the main parameters of the BJT-transistor in the common emitter connection. Familiarize yourself with the application possibilities of different types of BJT-transistors. Test devices BJT-transistors T, potentiometers R1, R2, DC-voltmeters V1, V2, DC-milliammeter A, DC-ammeter A2, connection wires. Test circuits Figure 5. Input characteristics of the BJT transistor Figure 6. Output characteristics of the BJT transistor 15

16 Procedure 1) Study the test devices, write down the types and the technical data of the transistors and measuring instruments (type, accuracy class etc). 2) Select the potentiometers and measuring instruments according to the parameters of the transistor. 3) Compile the test circuit given in Fig. 5. 4) Turn the voltage divider (potentiometer R1) until the voltage between base and emitter U BE = 0 and voltage between the collector and the emitter U KE = 0. 5) Take up the input characteristics I B = f(u BE ) of transistor, when the voltage between the collector and the emitter U KE = const., and for that purpose: keep the voltage U KE = 0 by the help of the potentiometer R 2 and change the voltage U BE = 0 U BEmax with a suitable step. Follow that U KE = 0! Sign up the values of U BE and I B (6 8 measurings); organize the results into a table; keep the voltage U KE = 5 V and repeate the previous measurings; organize the results into a table. 6) Compile the test circuit given in Fig. 6. 7) Take up the output characteristics I K = f(u KE ) of the transistor when I B = const., and for that purpose: by the help of the potentiometer R 1 set the required value of the base current I B. Change the voltage U KE = 0 U KEmax with a suitable step. Follow that I B = const! Sign up the values of U KE and I K (6-8 measurings); repeat the previous measurings with three different values of I B ; organize the results in a table. Analysis of observations 1) On the basis of the results draw the input characteristics I B = f(u BE ), when U KE = const. and the output characteristics I K = f(u KE ), when I B = const., of the transistor. Draw the load line on the output characteristics and choose the operating point. ΔI K I K max. I K min. 2) Calculate the current gain: β = =, (1) ΔI I I B B max. B min. ΔU BE 3) Calculate the input resistance: Rs =, (2) ΔI ΔU KE 4) Calculate the output resistance: Rv =, (3) ΔI 5) Conclusions. B K 16

17 4.4 Work no. 4. Single-phase ridge rectifier Objective To determine the voltage-current characteristics and the main parameters of the single-phase bridge rectifier. To determine the ripple factor without a filter and with different filters. Taking up the oscillograms of the output voltage and current. Familiarize yourself with the application possibilities of the single phase bridge rectifier. Test devices single-phase bridge rectifier, DC-ammeter A, AC-voltmeter V1, DC-voltmeter V2, inductor L, capacitor C, active load R k, oscilloscope. Test circuit Figure 7. Single phase bridge rectifier Procedure 1) Study the test devices, write down the types and the technical data of the diodes in the rectifier and measuring instruments (type, accuracy class etc); 17

18 2) Select the load potentiometer and measuring instruments according to the parameters of the rectifier. 3) Compile the test circuit given in Fig. 3 (without filters). 4) Regulate the resistance of the potentiometer R k to the maximum value. 5) To determine the output voltage-current characteristic U D = f(i D ) change the value of the rectified current I D with a suitable step from the minimum to the maximum value. Sign up the DCcomponents of the output voltage and current and AC-component of the rectified voltage (ripple voltage) U AC (6 8 measurings). 6) Organize the results into a table. 7) Take up the oscillogram of the output voltage. 8) Compile the test circuit with the C-filter. 9) Determine the ripple factor of the C-filter. Measure the DC and AC-components of the output voltage and take up the oscillogram of the output voltage. 10) Compile the test circuit with LC-filter. 11) Determine the ripple factor of LC-filter. Measure the DC and ACcomponents of output voltage and take up the oscillogram of the output voltage. 12) Organize the results into a table. Analysis of observations 1) On the basis of the results draw the output voltage-current characteristic U D = f(i D ). 2) Calculate the ripple factors without a filter: 2U AC r = 100%, (4) U D 3) Calculate the smoothing coefficients of filters: r q =, (5) r f where r ripple factor without a filter, r f ripple factor with a filter; 4) Conclusions. 18

19 4.5 Work no. 5. Operational amplifier Objective The use an operational amplifier. To acquire the voltage amplifying factor and the characteristics of the amplifying factor/ input signal frequency. Test devices 1) operational amplifier 2) power supply 3) signal generator 4) oscilloscope Test circuit 5V + - Signal generator R3 + U1 - R2 R1 Oscilloscope Figure 8. Operational amplifier Procedure 5) Study the test devices, write down the type and the technical data of the operational amplifier and the measuring instruments (type, accuracy class etc); 6) Connect all the needed devices according to Fig. 8. 7) Switch on all the devices. Set the signal generator output to the following parameters (signal amplitude 0.2 V, frequency 1 khz, waveform sinusoidal). 8) Turn all the potentiometers on the front panel of the operational amplifier test setup into the minimum position (R1, R2, R3). 9) Turn the potentiometer of the feedback R2 into the middle position. 10) Turn slowly the input signal offset regulator potentiometer R3 until the output signal is a normal sinusoidal wave without the upper or the lower part of the waveform cut off. 11) The gain of the operational amplifier. Turn the potentiometer of the feedback R2 into the zero position and increase the gain with eight or ten steps into the maximum position (until the output signal is 19

20 obstructed). Record the amplitude values of the output voltage for every step. 12) Calculate the gain of operational amplifier for different values of negative feedback. β = U U out _ amp in _ amp, where U out_amp is the value of the output voltage amplitude U in_amp is the value of the input voltage amplitude 13) Increase the output voltage until the upper part of the waveform is cut off. Record the amplitude value of the output signal. 14) Answer the question why part of the output signal is cut off at a certain gain level. 15) Set the signal generator output to the following parameters (signal amplitude 0.2 V, frequency 100 khz, waveform sinusoidal). Set the gain to its maximum value (output signal must be clear and sinusoidal). 16) Increase the frequency of the input signal with 100 khz step up to 1 MHz frequency. Record the frequency and the output signal amplitude. 17) Calculate by the help of equation 6 the gain of the operational amplifier for different frequencies. 18) Draw the characteristics of the input signal frequency / amplifier gain. (6) Analysis of observations 1) Answer the following questions. 2) In what kind of applications are the operational amplifiers used? 3) How is the output signal voltage or current regulated? 4) What purpose can the feedback be used for? 5) What kind of different feedback can be used? 20

Exercise 6 AC voltage measurements average responding voltmeters

Exercise 6 AC voltage measurements average responding voltmeters 1. Aim of the exercise The aim of the exercise is to familiarize students with the AC voltage measurements by means of rectified average