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Understanding BJT Base Bias: Calculations and Simulations Guide

School
San Jose State University**We aren't endorsed by this school
Course
TECH 63
Subject
Electrical Engineering
Date
Dec 10, 2024
Pages
12
Uploaded by CoachUniverse16269
Objectives: To understand the Bipolar Junction Transistor base bias operation.To understand the relation between voltages and currents in a BJT.List of Equipment:Solderless BreadboardPower Supply: Keysight EDU36311A, Triple Output, Programmable DC Power SupplyMultimeter: Keysight EDU34450A5½ Digit Digital MultimeterEquipment/Material:Multisim software running on PC5.1 kΩ resistors (Quantity 1)300 kΩ resistors (Quantity 1)1 MΩ resistors (Quantity 1)10 MΩ resistors (Quantity 1)2N3904 BJT (Quantity 1)
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Formulas from Lecture:𝑉?𝐸= 0. 7𝑉𝑉𝑅?= 𝑉??− 𝑉?𝐸𝐼?= (𝑉??−𝑉?𝐸)/𝑅?𝐼𝑐= β𝐼?𝑉?𝐸= 𝑉??− 𝐼?𝑅?Part I) Hand CalculationsStudy of Base-Biased BJTA. Perform hand calculation on the Base Biased BJT shown below with the following values: VBB= 5 V, VCC= 15 V, RB= 1 MΩ, RC= 5.1 kΩ. Assume βDC=200.Perform calculation showing the values of IB, IC, VBE, and VCEand record in the table shown.Please show the general equation, substitute numerical values, then write down the answers. You need to type this information using MS-Word Equation. B. Repeat part “A” with , RBchanged to 10 MΩ and include your information in the table below. Comment about the difference in the values ICand VCE.
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C. Repeat part “A” with , RBchanged to 300 kΩ and include your information in the table below. Comment about the difference in the values ICand VCE.Part II) Circuit simulation using MultisimA. Construct the above circuit in Multisim with the following values given in Part I (A), RB= 1 MΩ, and simulate the circuit. Include the simulated values in the table below and provide screenshots of the Multisim display.B. Repeat Part II “A” with RBchanged to 10 MΩ and include your information in the table below. Comment about the difference in the values ICand VCE.C. Repeat Part II “A” with RBchanged to 300 kΩ and include your information in the table below. Comment about the difference in the values ICand VCE.Analyze and compare the values for parts A, B, and C and comment about the behavior of the circuit.Calculate the percent error for the values.Part III) Circuit constructed on the breadboardPlease note the pinout for the npn BJT shown below:A. Construct the above circuit on the breadboard with the values given in Part I (A), RB= 1 MΩ, and test your circuit. Include the measured values in the table below and provide pictures of your constructed circuit on the breadboard.B. Repeat Part III“A” with, RBchanged to 10 MΩ and include your information in the table below. Comment about the difference in the values ICand VCE.C. Repeat Part III“A” with , RBchanged to 300 kΩ and include your information in the table below. Comment about the difference in the values ICand VCE.Analyze and compare the values for parts A, B, and C and comment about the behavior of the circuit.
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Calculate the percent error for the values.Post-Lab activities: Lab Report Preparation Place in your lab report the hand calculations, pictures of simulated circuit from Multisim, and the pictures of the working circuit on the breadboard. Include all information in the tables shown below:𝑉?𝐸= 0. 7𝑉𝐼?= (𝑉??−𝑉?𝐸)/𝑅?= (5𝑉 − 0. 7𝑉)/1𝑀Ω = 4. 3/1, 000, 000 = 4. 3µ? = 0. 0043𝑚?𝐼𝑐= β𝐼?= 200 * 4. 3µ? = 860µ? =. 86𝑚?𝑉?𝐸= 𝑉??− 𝐼?𝑅?=15𝑉−(860µ?*5. 1 𝑘Ω)860µ? * 5. 1𝑘Ω = 860 * 10−6? * 5100Ω = 4. 386𝑉𝑉?𝐸= 15𝑉 − 4. 386𝑉 = 10. 614𝑉VBB= 5 V, VCC= 15 V, RB= 1 MΩ, RC= 5.1 kΩ. Assume βDC=200.Data for Part I A, II A, and III A:IBICVBEVCEHand-Calculations Expected value. 0043𝑚?. 86𝑚?0.7V10. 61𝑉Multisim412.408mA634mA649.2mV11.87VBreadboard0.0049mA0.876mA0.674V10.87V%ErrorBetween Expected Value and Measured 13.95% error1.86% error3.71% error2.45% error
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Fig. 1-4 Multisim Circuit and Values for Ib, Ic, Vbc, VceFig. 5 Ib breadboard calculationFig. 6 Ic breadboard calculation
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Fig. 7 Vbe breadboard calculationFig. 8 Vce breadboard calculationData for Part I B, II B, and III B:𝑉?𝐸= 0. 7𝑉𝐼?= (𝑉??−𝑉?𝐸)/𝑅?= (5𝑉 − 0. 7𝑉)/10𝑀Ω = 4. 3/10, 000, 000 = 0. 43µ? =. 00043𝑚?𝐼𝑐= β𝐼?= 200 * 0. 43µ? = 86µ? = 0. 086𝑚?𝑉?𝐸= 𝑉??− 𝐼?𝑅?=15𝑉−(86µ?*5. 1 𝑘Ω)860µ? * 5. 1𝑘Ω = 86 * 10−6? * 5100Ω = 0. 4386𝑉𝑉?𝐸= 15𝑉 − 0. 4386𝑉 = 14. 5614𝑉VBB= 5 V, VCC= 15 V, RB= 10MΩ, RC= 5.1 kΩ. Assume βDC=200.
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Fig. 9-12 Multisim Circuit and Values for Ib, Ic, Vbc, VceIBICVBEVCEHand-Calculations (Expected Value). 00043𝑚?0. 086𝑚?0.7V14.56VMultisim412.41mA42mA579.1mV14.78VBreadboard0.0005mA0.0869mA0.716V14.13V%ErrorBetween Expected Value and Measured 16.28% error1.05% error2.29% error2.95% errorFig. 13 Ib breadboard calculation
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Fig. 14 Ic breadboard calculationFig. 15 Vbe breadboard calculationFig. 16 Vce breadboard calculation
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Data for Part I C, II C and III C:𝑉?𝐸= 0. 7𝑉𝐼?= (𝑉??−𝑉?𝐸)/𝑅?= (5𝑉 − 0. 7𝑉)/300𝑘Ω = 4. 3/300, 000Ω = 14. 33µ? =. 01433𝑚?𝐼𝑐= β𝐼?=200*14. 33µ?=2. 866 𝑚?𝑉?𝐸= 𝑉??− 𝐼?𝑅?=15𝑉−(2. 866 𝑚?*5. 1 𝑘Ω)860µ? * 5. 1𝑘Ω = 2. 866 * 10−3? * 5100Ω = 14. 6356𝑉𝑉?𝐸= 15𝑉 − 14. 6356𝑉 = 0. 3644𝑉VBB= 5 V, VCC= 15 V, RB= 300kΩ, RC= 5.1 kΩ. Assume βDC=200.Fig. 17-20 Multisim Circuit and Values for Ib, Ic, Vbc, VceIBICVBEVCEHand-Calculations (Expected Value)0.01433mA2. 866 𝑚?0. 7𝑉0.364VMultisim412.41mA2.483mA685.21mV3.923 VBreadboard0.837mA2.949mA0.758V0.137V%ErrorBetween Expected Value and Measured 5731% error2.89% error8.39% error62.34% error
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Fig. 21 Ib breadboard calculationFig. 22 Ic breadboard calculationFig. 23 Vbe breadboard calculation
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Fig. 23 Vce breadboard calculationQuestionsAnalyze the above measurements to answer the following questions: 1. Compare the hand calculated versus simulated values, and breadboard values. If they are not exactly the same then explain briefly why they are not exactly equal.They are not exactly the same because of variation among the breadboard and multisim, the equipment may be defective or parts may have been worn down not to mention human error which will result in different values2. What do you observe regarding the relationship between the values of ICand VCEfor parts A, B, and C.There is not much of a correlation between A and C seem to share similarities but B is much lower 3. What is the relation between different Q-points in parts A, B, and C (either closer to cut-off, closer to saturation, or in-between saturation and cut-off).Closer to cut-off4. From your experimental results have you gained a good understanding of BJT biasing.YesChallenges EncounteredFor this lab the breadboard portion of the lab was the most challenging. First figuring out how to set up the bread board took numerous trials to get right. From there getting the values that were expected for each part was hard. However we were to get close to all expected values. The only two we could not get close too was in part C Ib and Vce were greatly off. For Ib we were
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not able to get close to the expected value at all causing an alarming percent error. This is the same fro Vce but it was more reasonable and some what close but still gave a high percent error. ConclusionAfter completing lab 9, as we were introduced to BJT. We had trouble figuring out the multimeters as we did not calibrate it correctly and this led to a lot of confusion as this led to us getting After completing the lab we learned many new things such as connecting our alligator clips directly to the componentry on the breadboard instead of having many jumper cables by doing this it simplified our design and made the construction of the circuit more efficient. We also learned how to properly use and set up a DMM and DO when dealing with half wave rectifiers and now we are more confident in our practices
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