LW6 - NPN and PNP BJT Characterization

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University of Cincinnati, Main Campus *

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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

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

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