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| university:courses:electronics:electronics-lab-5fr [24 Jul 2017 15:19] – change amplitude value to peak-peak Antoniu Miclaus | university:courses:electronics:electronics-lab-5fr [25 Jun 2020 22:07] (current) – external edit 127.0.0.1 |
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| <WRAP centeralign> Figure 2: Low-frequency equivalent circuit. </WRAP> | <WRAP centeralign> Figure 2: Low-frequency equivalent circuit. </WRAP> |
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| Using short-circuit time constant analysis, the lower 3-dB frequency (?<sub>L</sub>) can be found as: | Using short-circuit time constant analysis, the lower 3-dB frequency (ω<sub>L</sub>) can be found as: |
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| {{ :university:courses:electronics:afr_e1.png?250 |}} | {{ :university:courses:electronics:afr_e1.png?250 |}} |
| <WRAP centeralign> Figure 3: High-frequency equivalent circuit. </WRAP> | <WRAP centeralign> Figure 3: High-frequency equivalent circuit. </WRAP> |
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| The higher 3-dB frequency (?<sub>H</sub>) can be derived as: | The higher 3-dB frequency (ω<sub>H</sub>) can be derived as: |
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| {{ :university:courses:electronics:afr_e5.png?320 |}} | {{ :university:courses:electronics:afr_e5.png?320 |}} |
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| V<sub>CC</sub> = 5 V\\ | V<sub>CC</sub> = 5 V\\ |
| R<sub>S</sub> = 50?\\ | R<sub>S</sub> = 50Ω\\ |
| R<sub>L</sub> = 1 k?\\ | R<sub>L</sub> = 1 kΩ\\ |
| R<sub>IN</sub> > 250\\ | R<sub>IN</sub> > 250\\ |
| Isupply < 8mA\\ | Isupply < 8mA\\ |
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| 1. Show all your calculations, design procedure, and final component values.\\ | 1. Show all your calculations, design procedure, and final component values.\\ |
| 2. Verify your results using a circuit simulator (TINA, QUCS, PSpice). Submit all necessary simulation plots showing that the specifications are satisfied. Also provide the circuit schematic with DC bias points annotated.\\ | 2. Verify your results using the LTSpice circuit simulator. Submit all necessary simulation plots showing that the specifications are satisfied. Also provide the circuit schematic with DC bias points annotated.\\ |
| 3. Using the simulator, find the higher 3-dB frequency (f<sub>H</sub>) while C<sub>F</sub> = 0.\\ | 3. Using the LTSpice simulator, find the higher 3-dB frequency (f<sub>H</sub>) while C<sub>F</sub> = 0.\\ |
| 4. Determine Cp, Cµ and r<sub>b</sub> of the transistor from the simulated operating point data, (refer to your simulator's documentation on how to obtain operating point data). Calculate f<sub>H</sub> using the equation from section 1.3 and compare it with the simulation result obtained in Step 3. Remember that the equation gives you the radian frequency and you need to convert to Hz.\\ | 4. Determine Cp, Cµ and r<sub>b</sub> of the transistor from the simulated operating point data, (refer to your simulator's documentation on how to obtain operating point data). Calculate f<sub>H</sub> using the equation from section 1.3 and compare it with the simulation result obtained in Step 3. Remember that the equation gives you the radian frequency and you need to convert to Hz.\\ |
| 5. Calculate the value of C<sub>F</sub> to have f<sub>H</sub> = 50 kHz. Simulate the circuit to verify your result, and adjust the value of C<sub>F</sub> if necessary.\\ | 5. Calculate the value of C<sub>F</sub> to have f<sub>H</sub> = 50 kHz. Simulate the circuit to verify your result, and adjust the value of C<sub>F</sub> if necessary.\\ |
| 1 - small signal NPN transistor (2N3904)\\ | 1 - small signal NPN transistor (2N3904)\\ |
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| Note on the source resistor R<sub>S</sub> and the AWG output of the ADALM2000. The AWG output has a 50 Ω series output resistance and you will need to include it along with the external resistance in series with its output. Also because of the relatively high gain of your design you will need an input signal with a small amplitude of around 100mV. Rather than turning down the AWG in software is would be better from a noise point of view to insert a resistor voltage divider between the AWG output and your circuit input to attenuate the signal. Using something like that shown in figure 4 will provide both an attenuation factor of 1/8 and a 60Ω equivalent source resistance. Other combinations of resistor values are of course also possible based on what you have available. | Note on the source resistor R<sub>S</sub> and the AWG output of the ADALM2000. The AWG output has a 50 Ω series output resistance and you will need to include it along with the external resistance in series with its output. Also because of the relatively high gain of your design you will need an input signal with a small amplitude of around 100mV peak-to-peak. Rather than turning down the AWG in software it would be better from a noise point of view to insert a resistor voltage divider between the AWG output and your circuit input to attenuate the signal. Using something like that shown in figure 4 will provide both an attenuation factor of 1/8 and a 60Ω equivalent source resistance. Other combinations of resistor values are of course also possible based on what you have available. |
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| {{ :university:courses:electronics:afr_f4.png?400 |}} | {{ :university:courses:electronics:afr_f4.png?400 |}} |
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| <WRAP centeralign> Figure 4 Signal attenuator with 60Ω source resistance </WRAP> | <WRAP centeralign> Figure 4 Signal attenuator with 60Ω source resistance </WRAP> |
| | ====Hardware Setup==== |
| | Construct the circuit on your breadboard. |
| | {{ :university:courses:electronics:afr_nf5.png? |}} |
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| | <WRAP centeralign> Figure 5 Common Emitter BJT amplifier breadboard connection</WRAP> |
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| ==== Directions: ==== | ==== Directions: ==== |
| 7. Prepare a data sheet showing your simulated and measured values.\\ | 7. Prepare a data sheet showing your simulated and measured values.\\ |
| 8. Be prepared to discuss your experiment with your TA. Have your lab data sheet checked off by your TA before submitting the lab report. | 8. Be prepared to discuss your experiment with your TA. Have your lab data sheet checked off by your TA before submitting the lab report. |
| | {{ :university:courses:electronics:afr_nf6.png?500 |}} |
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| For further experimentation replace each capacitor with ones that are factors of 2 and 10 larger and smaller than your design values and re-measure the response curve with the Network Analyzer instrument. Do this to only one capacitor at a time to observe its individual effect on the response. Explain the changes in the response that you see. | <WRAP centeralign> Figure 6 Scopy Network Analyzer plot with C<sub>F</sub> = 0 </WRAP> |
| | {{ :university:courses:electronics:afr_nf7.png?500 |}} |
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| **Return to Lab Activity [[university:courses:electronics:labs|Table of Contents]]** | <WRAP centeralign> Figure 7 Scopy Oscilloscope plot with C<sub>F</sub> = 0 at frequency = 500Hz</WRAP> |
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| | For further experimentation replace each capacitor with ones that are factors of 2 and 10 larger and smaller than your design values and re-measure the response curve with the Network Analyzer instrument. Do this to only one capacitor at a time to observe its individual effect on the response. Explain the changes in the response that you see. |
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| | <WRAP round download> |
| | **Resources** |
| | * LTSpice files: [[downgit>education_tools/tree/master/m2k/ltspice/freq_resp_bjt_ltspice | freq_resp_bjt_ltspice]] |
| | * Fritzing files: [[downgit>education_tools/tree/master/m2k/fritzing/freq_resp_bjt_bb | freq_resp_bjt_bb]] |
| | </WRAP> |
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| | **Return to Lab Activity [[university:courses:electronics:labs|Table of Contents]]** |
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