LW6 - NPN and PNP BJT Characterization

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2070

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Electrical Engineering

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Dec 6, 2023

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College of Engineering and Applied Science Department of Electrical Engineering and Computer Science EECE 2070L LW6 NPN and PNP BJT Characteristics Background: Diodes, NPN and PNP BJTs can be characterized using a device called a curve tracer. We have two of these devices in the department, they are very useful for quickly characterizing a Semiconductor device that has been designed by researchers. However often in industry this device is a luxury because of its limited use and high price tag. In this lab you will learn how to use a DMM to perform a test on a BJT that will ensure that it is still functional. You will also characterize an NPN and PNP transistor using the Analog Discovery 2 curve tracer board. Objective: Observe the relationship between the collector current and the base current for the 2N3904 NPN and the 2N3906 PNP Bipolar Transistor (BJT). Procedure: Part 1: Diode Functionality Test Some DMMs have an h fe measurement, like the DMM in your kit. 1. Using the DMM in your kit use the h fe measurement, keep in mind these are not the best meters and it might not work. Either way, I need you to record what screen displays and take a picture of it. If you do not have it with you, borrow one. a. DMM h fe measurement = 207 h fe 1b EECE 2070L Updated Sept 2023

College of Engineering and Applied Science Department of Electrical Engineering and Computer Science Measured value of hfg for the NPN transistor using handheld DMM. Figure 0: DMM hfg measurement The Diode check function of DMM can be used to test if a BJT is operational. This works 99.9 percent of the time. There has been only one instance in over 8 years where the transistor was faulty, and this test said it was OK. The curve tracer characterization of that BJT indicated it was faulty. A BJT has three regions, in the case of an NPN BJT, you have small lightly doped P-type material at the Base sandwiched between a heavily doped N-type Emitter and lighter doped N- type Collector. A diode has just the N and P type material sandwiched together. This means that the diode test can be used to verify that these junctions are still intact. Figure 1 is a schematic of a NPN test example. In the reverse bias a word should be displayed, type that word in the table provided. 1. Using the Diode Test on the DMM, Test a 2N3904 NPN BJT and record the junction combinations of transistor listed in Figure 2. 2b EECE 2070L Updated Sept 2023

College of Engineering and Applied Science Department of Electrical Engineering and Computer Science Q1 2N3904 B E C B C E XMM1 Figure 1: NPN Forward Bias Base to Emitter Test Example NPN Test Base/Collector Junction Base/Emitter Junction Positive lead on the Base .70v .70v Negative lead on the base Open Open Figure 2: NPN Diode Test Results 2. Using the Diode Test on the DMM, test a 2N3906 PNP BJT and record the junction combinations of transistor listed in Figure 4. Q1 2N3906 B E C B C E XMM1 Figure 3: PNP Forward Bias Base to Emitter Test Example PNP Test Base/Collector Junction Base/Emitter Junction Positive lead on the Base Open Open Negative lead on the Base 0.74v 0.74v Figure 4: PNP Diode Test Results Part 2: Curve Tracing using the Analog Discovery 2 (AD2) Connect the AD2 to your laptop with the USB cord. Next plug the transistor into the breadboard so each pin is in its own row. Wire each transistor pin to the correct terminal ensuring that none of the wire insulation is caught in the connection clamp as seen in Figure 5. 3b EECE 2070L Updated Sept 2023

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College of Engineering and Applied Science Department of Electrical Engineering and Computer Science Figure 5: Connection Example 3. Next open the Waveforms software and follow the video on how to set up the WaveForms transistor test. Use units of milliamps for current and round each value to 2 decimal places. Record your data in Figure 6. Depiction of the voltage and amperage of NPN Transistor Wave form for varying Vce and Ic. I C Ide al At V CE = 4v At V CE = 5v At V CE = 6v I C I B V BE V C E I C I B V BE V C E I C I B V BE V CE 1.5 m A 1.380 9mA 7.690 4 uA 0.67 183v 3.95 79v 1.380 9mA 7.723 7uA 0.67 183v 5.05 52v 1.417 6mA 7.6911 uA 0.67 15v 6.05 02v 2m A 2.114 2mA 0.011 63mA 0.68 319v 3.97 98v 2.150 9mA 0.011 67mA 0.68 319v 4.97 84v 2.187 5mA 0.0116 7mA 0.68 319v 5.97 34v 3.5 m A 3.397 5mA 0.018 17mA 0.69 554v 3.96 15v 3.397 5mA 0.018 14mA 0.69 521v 5.05 52v 3.434 1mA 0.0182 mA 0.69 521v 5.95 14v 4m A 4.204 1mA 0.022 56mA 0.70 155v 3.97 62v 4.204 1mA 0.022 56mA 0.70 122v 5.06 99v 4.247 mA 0.0225 6mA 0.70 089v 5.96 61v Figure 6: NPN I C Data 4. Once your data is recorded. Take a screenshot of the entire UI (I want to see the settings and both axes) with traces visible. Insert it below give it an introduction sentence and caption. Your screen shots should look similar to the operating region of characteristic curves in your textbook on page 297 Figure 5.14 4b EECE 2070L Updated Sept 2023

College of Engineering and Applied Science Department of Electrical Engineering and Computer Science Trace curve of NPN transistor depicting values for Ic ideal equals 1.5mA and Vce ideal equals 4v. Figure 6.1: NPN I C Data Trace Curve 5. Using your data from Figure 6, calculate Beta (β) where, β = I C I B (1) for all the Measured I C /I B combinations above. Fill in the table in Figure 7 with your derived Beta measurements. (A derived measurement is a value calculated from measurements with no assumed or “ideal” values in the calculation). I C Ideal Ideal β From Prework β @ V CE = 4V β @ V CE = 5V β @ V CE = 6V 5b EECE 2070L Updated Sept 2023

College of Engineering and Applied Science Department of Electrical Engineering and Computer Science 1.5mA 145 180 179 184 2mA 150 182 185 189 3.5mA 160 188 188 189 4mA 165 188 188 189 Figure 7: NPN Beta Calculation Data There could be significant differences between your calculated and measured values. This is okay … to an extent. If you calculate a Beta over 270 ask your in instructor or TA if it is okay. 6. Remove the 2N3904 NPN transistor and replace it with the 2N3906 PNP transistor. Change the transistor type from NPN to PNP in the dropdown menu next to the RUN button in the Waveforms UI. You may need to adjust settings a little I would run it with your previous settings before adjusting anything. I C Id eal At V CE = 4v At V CE = 5v At V CE = 6v I C I B V B E V C E I C I B V B E V C E I C I B V BE V CE 1 m A - 1.18 55m A - 8.41 816u A - 0.6 745 7v - 3.9 834 3v - 1.22 219 mA - 8.45 147u A - 0.6 745 7v - 5.0 808 v - 1.258 85m A - 8.41 816u A - 0.6 745 7v - 5.9 769 9v 2. 5 m A - 2.68 874 mA - 0.01 654 mA - 0.6 926 v - 4.0 309 9v - 2.72 54m A - 0.01 655 mA - 0.6 922 7v - 4.9 235 1v - 2.798 73m A - 0.01 658 mA - 0.6 722 7v - 5.9 184 6v 3 m A - 3.23 87m A - 0.01 943 mA - 0.6 972 8v - 3.9 761 2v - 3.34 869 mA - 0.01 947 mA - 0.6 966 1v - 5.0 698 3v - 2.835 39m A - 0.01 658 mA - 0.6 922 7v - 6.0 172 3v 4. 5 m A - 4.37 528 mA - 0.02 535 mA - 0.7 042 9v - 4.0 602 5v - 4.48 527 mA - 0.02 535 mA - 0.7 039 5v - 5.0 515 4v - 4.595 26m A - 0.02 538 mA - 0.7 036 2v - 6.0 428 3v Figure 8: PNP I C Data 6b EECE 2070L Updated Sept 2023

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College of Engineering and Applied Science Department of Electrical Engineering and Computer Science Trace curve of PNP transistor depicting values for Ic ideal equals 4.5 mA at Vce ideal equals 6v. Figure 9.1: PNP I C Data Trace Curve 7. Using your data from Figure 8, calculate Beta (β) where, 7b EECE 2070L Updated Sept 2023

College of Engineering and Applied Science Department of Electrical Engineering and Computer Science β = I C I B (1) for all the Measured I C /I B combinations above. Fill in the table in Figure 6 with your derived Beta measurements. (A derived measurement is a value calculated from measurements with no assumed or “ideal” values in the calculation). I C Ideal Ideal β From Prework I B Ideal From Prework β @ V CE = 4V β @ V CE = 5V β @ V CE = 6V 1mA 150 .0067mA 140 145 150 2.5mA 150 .0167mA 163 165 170 3mA 155 .0194mA 167 173 172 4.5mA 155 .0290mA 173 177 182 Figure 10: PNP Beta Calculation Data Principles of Operation: 1. Within its operating range, what kind of source (voltage or current) does a BJT act like? How is it controlled? Explain. A BJT acts like a current source when it’s in its operating range because the output current is dependent on the input currents which is given by the ratio of I C I B . A BJT uses the base current in order to control the flow of current from the emitter terminal to the collector end of the BJT. Analysis: Using data from Figure 7, calculate the percent error between the Ideal beta you found on the Data sheet and your derived measurements from lab. Show one example calculation typed out with values from your data and then present your present error data in table below it. ¿ Theoretical − Experimental ∨ ¿ Theoretical ∗ 100% % Error = ¿ ¿ 145 − 180 ∨ ¿ 145 ∗ 100% = 24.14% % Error = ¿ Percent Error β @ V CE = 4V Percent Erro β @ V CE = 5V Percent Error β @ V CE = 6V 24.14% 23.45% 26.9% 21.33% 23.33% 26% 17.5% 12.5% 18.13% 14.0% 14.0% 14.55% 8b EECE 2070L Updated Sept 2023

College of Engineering and Applied Science Department of Electrical Engineering and Computer Science 1. Using data from Figure 9, calculate the percent error between the Ideal beta you found on the Data sheet and your derived measurements from lab. Show one example calculation typed out with values from your data and then present your present error data in table below it. 2. ¿ Theoretical − Experimental ∨ ¿ Theoretical ∗ 100% % Error = ¿ 3. % Error = | 150 − 140 | 150 ∗ 100% = 6.67% I C Ideal Ideal β From Prework Precent Error β @ V CE = 4V Percent Error β @ V CE = 5V Percent Error β @ V CE = 6V 1mA 150 6.67% 3.33% 0% 2.5mA 150 8.67% 10.0% 13.33% 3mA 155 7.74% 11.61% 11.61% 4.5mA 155 11.61% 14.19% 17.42% Conclusion: 1. How does the DMM test at the beginning of the lab help you with future lab experiments? The DMM test will help in future labs to help troubleshoot. For example, we can use the test to see if our transistor or diode are even working using the diode test. Since our components are bought in bulk, some of the components may not even work as intended in the first place. 2. In lab I typically use 0.7v for the base-emitter voltage drop (V BE ). Looking at the V BE data in Figures 6 and 8, based on your data: a. Do you feel this is still a safe design assumption? Why or why not? Yes, because if you look at both figure 6 and 8, the V BE values tend to be right around the 0.7v range. 9b EECE 2070L Updated Sept 2023

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College of Engineering and Applied Science Department of Electrical Engineering and Computer Science b. Have you used a different value in your lecture class? If yes, what was/is it? Yes, in lecture we have used values such as 0.6 to solve example problems. Appendix: 10b EECE 2070L Updated Sept 2023