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Introduction In this experiment we will learn how to measure the DC Characteristics of Bipolar Junction Transistors (BJTs). The relationships between voltages and currents in a BJT determine its performance and DC characteristics. We will draw the characteristic Ic vs. Vce curves and will measure the B for the transistor. Read the Lab outline entirely before starting your work. Remember that your lab report will need to include your measurements, calculations, screenshots, etc. as indicated at the end of this outline. Procedure 1. Collector Characteristics 1.1 Start this lab by building the circuit shown in Figure 4.1 3 R2 R3 R1 4 5 5kQ 50% V1 1kQ Key=B - 20 V 1MQ 50% Key=A Q1 1 R4 2 330kQ 2N3904 Figure 4. 1: Circuit to measure collector characteristics You will notice that this circuit uses a potentiometer. Locate the appropriate potentiometers in the Library as shown in Figure 4.2 Select a Component Database: Component: Symbol (ANSI) OK Master Database 1k O Close Group: 10 w Basic 20 50% Search 50 1 Family: Detail Report 100 Model. TRANSFORMER 200 Save unique component on placement NON_LINEAR_TRANSF 500 Help 1k Component type: Z_LOAD 2k <no type=""> RELAY 5k CONNECTORS 10k SCH_CAP_SYMS 20k RESISTOR 50k Model manuf. /ID: CAPACITOR 100k Generic/VIRTUAL_POT INDUCTOR 200k 500k Footprint manuf./Type: 1M VARIABLE_CAPACITOF <no footprint=""> 2M Generic/LIN_POT VARIABLE_INDUCTOR 5M POTENTIOMETER Hyperlink: III N Components: 18 Searching: Figure 4. 2: library for potentiometers 1.2 Double clicking each potentiometer will allow us to set its parameters are shown in Figure 4.3 Potentiometer - Label Display Value Fault Pins User Fields R5 Resistance (R) 1k a 1kQ Key: A Key=A 50% Increment: 5 % Component Type: Hyperlink: Layout Settings Footprint: Edit Footprint Manufacturer: Replace OK Cancel Info Help Figure 4. 3: Parameters for potentiometers </no></no>The Parameter "Key" indicates that key in your keyboard that will result in changing the value of the potentiometer. Note that by default Mulstim assigns the key 'A' to all potentiometers. Change them so each potentiometer responds to a different key. This will allow you to change the values of each one independently. The other parameter that we want to change is "Increment" Change it from the default value of 5% to 1%. This will allow us to fine tune the values as needed. Also note that it is possible to change the values of the potentiometers during the simulation. In doing so, allow few second for the values to stabilize before recording your measurements. 1.3 Adjust the potentiometer R1 and measure the voltage across R4 until it reaches approximately 3.3 V. This indicates a base current lb = 10 A 1.4 Change now the 5 kQ potentiometer R2 until the voltage Vce is approximately 2.0 V 1.5 With a DMM measure the collector current Ic (Remember that the DMM must be connected in series with the circuit and must be configured to measure Amps in DC). Record these values. 1.6 Repeat 1.5 for the following values of Vce: 2V, 4V, 6V, 8V, 10V, 12V, 14V, 16V 1.7 Using a Scatterplot in Excel or similar software, plot the value Ic versus Vce. You should obtain a graph similar to the one shown in Figure 4.4 for just one value of lb. In this case, the value of lb was 10 A. If your plot looks extremely different, review your work. Ic (mA) 8 90 A 7 80 A 70 6 60 ua on) 5 50 A 40 A 4 30A 3 (Active region) 20 A 2 10 4A 1 1B = 0 ua 5 10 15 20 Vce (V) Vcesat Cutallanian) Figure 4. 4: Typical Ic vs Vce for a BJT 1.8 We will adjust potentiometer R1 until the voltage measured across R4 reaches approximately 6.6 V. This indicates a base current lb = 20 A. 1.9 Keeping lb = 20 A, measure the value of the collector current Ic for the following values of Vce: 2V, 4V, 6V, 8V, 10V, 12V, 14V 1.10 Plot the on the same graph as you did in 1.7. 1.11 Change R1 again until lb = 30 A 1.12 Keeping lb = 30 A, measure the value of the collector current Ic for the following values of Vce: 2V, 4V, 6V, 8V, 10V. Plot them again. 1.13 Change R1 again until lb = 40 A 1.14 Keeping lb = 40 A, measure the value of the collector current Ic for the following values of Vce: 2V, 4V, 6V, 8V. Plot them again. You should now have obtained a graph similar to the one shown in Figure 4.4. 1.15 Find the highest and lowest value of ß. Remember that ß = Ic/lb. What can you conclude about the factors that affect the ß of a transistor? 2.- Using the Curve Tracer 2.1 Connect the curve tracer (IV - Analyzer) that we used in a previous lab to the 2N3904 transistor. Keep in mind that the transistor must be disconnected from the circuit. Double clicking the curve tracer will indicate where to connect each terminal. 2.2 Click on the Simulate Param. Button in the Curve Tracer to open the dialog box that will set the parameters for the analysis. We will use the same parameters used in Section 1: Start Vce = 0 V Start lb : 10 A Stop Vce = 16 V Stop lb: 50 A Increment: 1V Num-steps: 5 IV Analyzer-XIV1 E3 Components: BJT PNP Simulate Parameters x Current Range(A) Log Lin Source Name:V_ce Source Name: I_b F 2 kA Start: Start: A I -100 A V 10 Stop: 16 V Stop: 50 mA Voltage Range(V) Increment: 1 V Num steps: 5 Log Lin F 50 V Normalize Data I -50 V OK Cancel Reverse Simulate Param. b e Vce lb Figure 4. 5: Parameters for Curve Tracer 2.3 Run the simulation and observe the output of the instrument. Compare this to the results obtained in section 1. Use the cursor for more details. 3.- Measuring ß in a BJT 3.1 Build the circuit shown in Figure 4.6 R1 2.7kQ 1 R2 2 1MQ Q1 3 V1 20 V 2N3904 Figure 4. 6: Circuit to measure ß 3.2 Measure in the circuit lb and Ic lb = Ic = 3.3 Calculate the ß for the 2N3904 transistor Laboratory Report Create a laboratory report using Word or another word processing software that contains at least these elements: - Introduction: what is the purpose of this laboratory experiment? - Results for each section : Measured and calculated values, calculations, etc. following the outline. Include screenshots for the circuits and waveforms as necessary -- You can press Alt + Print_Screen inside Multisim or if using Windows 7, you can use the "Snipping tool". Either way, you can paste these figures into your Word processor. Also include here the charts and graphs that you have created with the data you have collected. - Conclusion : What area(s) you had difficulties with in the lab; what did you lean in this experiment; how it applies to your coursework and any other comments. Introduction In this experiment we will explore the different methods for biasing BJT transistors. Read the Lab outline entirely before starting your work. Remember that your lab report will need to include your measurements, calculations, screenshots, etc. as indicated at the end of this outline. Procedure 1.- Emitter-bias configuration 1.1 Consider the circuit in Figure 5.1. Calculate the following parameters: lb, Ic, Vce, Vc, Ve, Vb (Use the value of ß calculated in Module 4 Lab). R2 2kQ 1 R3 3 430kQ Q1 V1 2 20 V 2N3904 4 R1 1kQ Figure 5. 1: Emitter-bias Configuration 1.2 Build the circuit of Figure 5.1 and measure these parameters. 1.3 Compare the calculated versus the measured values. 2. Voltage-divider bias configuration. 2.1 Consider the circuit in Figure 5.2. Calculate the following parameters: lb, Ic, Vce, Vc, Ve, Vb (Use the value of ß calculated in Module 4 Lab or the value calculated in Section 1 of this lab). 7. R5 10kQ R6 5 39kQ Q2 9 V2 - 20 V 2N3904 R7 8 3.9kQ R4 1.5kQ - - Figure 5. 2: Voltage-divider bias configuration 2.2 Build the circuit in Figure 5.2 and measure the same parameters. 2.3 Compare the calculated versus the measured values. 3. Collector-feedback bias configuration 3.1 Consider the circuit in Figure 5.3. Calculate the following parameters: lb, Ic, Vce, Vc, Ve, Vb (Use the appropriate value of ß). 6 R9 2kQ 12 R10 430kQ Q3 V3 11 20 V 2N3904 10 R8 1kQ - Figure 5. 3: Collector-bias configuration 3.2 Build the circuit in Figure 5.3 and measure the same parameters. 3.3 Compare the calculated vs the measured values. Laboratory Report Create a laboratory report using Word or another word processing software that contains at least these elements: - Introduction: what is the purpose of this laboratory experiment? - Results for each section : Measured and calculated values, calculations, etc. following the outline. Include screenshots for the circuits and waveforms as necessary -- You can press Alt + Print_Screen inside Multisim or if using Windows 7, you can use the "Snipping tool". Either way, you can paste these figures into your Word processor. - Conclusion : What area(s) you had difficulties with in the lab; what did you lean in this experiment; how it applies to your coursework and any other comments.

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