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university:courses:electronics:electronics-lab-pn-junction-cap [23 Mar 2017 15:43] – [Hardware Setup:] Doug Merceruniversity:courses:electronics:electronics-lab-pn-junction-cap [27 Jan 2021 22:36] (current) – use wp> interwiki links Robin Getz
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-====== Activity, The voltage dependent capacitance of the PN junction ======+====== Activity: The voltage dependent capacitance of the PN junction ======
  
 ===== Objective: ===== ===== Objective: =====
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 For further reading on PN junction depletion region: For further reading on PN junction depletion region:
  
-[[http://en.wikipedia.org/wiki/Depletion_region|Depletion Region]]+[[wp>Depletion_region|Depletion Region]]
  
 ===== Materials: ===== ===== Materials: =====
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 Red, yellow and green LEDs\\ Red, yellow and green LEDs\\
 1 - 2N3904 NPN transistor\\ 1 - 2N3904 NPN transistor\\
-1 - 2N3906 PNP transistor\\ +1 - 2N3906 PNP transistor\\ 
  
 ===== Directions Step 1: ===== ===== Directions Step 1: =====
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 ===== Hardware Setup: ===== ===== Hardware Setup: =====
  
-Using the Network Analyzer instrument in the Scopy software obtain a gain (attenuation) vs. frequency plot from 100 Hz to 10 MHz. Scope channel 1 is the "filter" input and scope channel 2 is the "filter" output. Set AWG offset to 1V and the Amplitude to 100mV with the Max-Gain set to 0.1X. The offset value is not important at this point when measuring a simple real capacitor but will be used as the reverse bias voltage when we measure diodes in later steps. Set the vertical scale to start at 1dB with an 80 dB range. Run a single sweep and export the data to a .csv file. You should notice a high pass characteristic that has a high attenuation at very low frequencies where the impedance of the capacitor is large compared to R<sub>1</sub>. At the very high end of the frequency sweep there should be a relatively flat region where the impedance of the C<sub>1</sub>, C<sub>m</sub>capacitive voltage divider is much lower than R<sub>1</sub>.+Using the Network Analyzer instrument in the Scopy software obtain a gain (attenuation) vs. frequency plot from 5 kHz to 10 MHz. Scope channel 1 is the "filter" input and scope channel 2 is the "filter" output. Set AWG offset to 1V and the Amplitude to 200mV peak-to-peak . The offset value is not important at this point when measuring a simple real capacitor but will be used as the reverse bias voltage when we measure diodes in later steps. Set the vertical scale to start at 1dB to -50 dB range. Run a single sweep and export the data to a .csv file. You should notice a high pass characteristic that has a high attenuation at very low frequencies where the impedance of the capacitor is large compared to R<sub>1</sub>. At the very high end of the frequency sweep there should be a relatively flat region where the impedance of the C<sub>1</sub>, C<sub>m</sub>capacitive voltage divider is much lower than R<sub>1</sub>.
  
 {{ :university:courses:electronics:apn_f3.png?600 |}} {{ :university:courses:electronics:apn_f3.png?600 |}}
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 ===== Procedure Step 1: ===== ===== Procedure Step 1: =====
 +{{ :university:courses:electronics:apn_f3_ss.png? |}}
 +
 +<WRAP centeralign> Figure 4 Scopy shot </WRAP>
  
 We chose C<sub>1</sub> to be sufficiently larger than C<sub>stray</sub> such that we can ignore C<sub>stray</sub> in our calculations but still have a similar value to our unknown C<sub>m</sub>. We chose C<sub>1</sub> to be sufficiently larger than C<sub>stray</sub> such that we can ignore C<sub>stray</sub> in our calculations but still have a similar value to our unknown C<sub>m</sub>.
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 {{ :university:courses:electronics:apn_e1.png?220 |}} {{ :university:courses:electronics:apn_e1.png?220 |}}
  
-[[http://en.wikipedia.org/wiki/Voltage_divider#Capacitive_divider|Capacitive Dividers]]+[[wp>Voltage_divider#Capacitive_divider|Capacitive Dividers]]
  
 ===== Directions Step 2: ===== ===== Directions Step 2: =====
  
-Now we will measure the capacitance of the various diodes from the Analog Parts Kit under a range of reverse bias conditions. Build the test setup as shown in figures 4 and 5 on your solder-less bread board. Simply replace C<sub>1</sub> with D<sub>1</sub>, a 1N4001. Be sure to insert the diode with the correct polarity such that a positive offset in AWG1 will reverse bias the diode.+Now we will measure the capacitance of the various diodes from the ADALP2000 Analog Parts Kit under a range of reverse bias conditions. Build the test setup as shown in figures 4 and 5 on your solder-less bread board. Simply replace C<sub>1</sub> with D<sub>1</sub>, a 1N4001. Be sure to insert the diode with the correct polarity such that a positive offset in AWG1 will reverse bias the diode.
  
 {{ :university:courses:electronics:apn_f4.png?600 |}} {{ :university:courses:electronics:apn_f4.png?600 |}}
- 
-<WRAP centeralign> Figure 4 Step 2 setup to measure diode capacitance </WRAP> 
- 
-{{ :university:courses:electronics:apn_f5.png?600 |}} 
  
 <WRAP centeralign> Figure 5 Step 2 setup to measure diode capacitance </WRAP> <WRAP centeralign> Figure 5 Step 2 setup to measure diode capacitance </WRAP>
 +
  
 ===== Hardware Setup: ===== ===== Hardware Setup: =====
 +{{ :university:courses:electronics:apn_f5.png?600 |}}
  
-Using the Network Analyzer instrument in the Scopy software obtain a gain (attenuation) vs. frequency plot from 100 Hz to 10 MHz for each AWG 1 DC offset value in table 1. Export the data for each sweep to a different .csv file.+<WRAP centeralign> Figure 6 Step 2 setup to measure diode capacitance </WRAP> 
 + 
 +Using the Network Analyzer instrument in the Scopy software obtain a gain (attenuation) vs. frequency plot from 5 kHz to 10 MHz for each AWG 1 DC offset value in table 1. Export the data for each sweep to a different .csv file.
  
 ===== Procedure: ===== ===== Procedure: =====
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 Table 1 Capacitance vs. voltage data Table 1 Capacitance vs. voltage data
 +{{ :university:courses:electronics:apn_f7_ss.png? |}}
 +
 +<WRAP centeralign> Figure 7 Scopy shot with offset at 0V</WRAP>
  
 Replace the 1N4001 diode with the 1N3064 diode from the Kit and repeat the same set of sweeps you just did for the first diode. Fill out another table with your measured data and calculated C<sub>diode</sub> values. How do the 1N3064 values compare to those for the 1N4001 diode? You should include a plot of the diode capacitance vs. reverse bias voltage for each diode you measure in your lab report. Replace the 1N4001 diode with the 1N3064 diode from the Kit and repeat the same set of sweeps you just did for the first diode. Fill out another table with your measured data and calculated C<sub>diode</sub> values. How do the 1N3064 values compare to those for the 1N4001 diode? You should include a plot of the diode capacitance vs. reverse bias voltage for each diode you measure in your lab report.
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 ===== Extra Credit measurements: ===== ===== Extra Credit measurements: =====
  
-Light emitting diodes or LEDs are also PN junctions. They are fabricated from materials other than Silicon so their turn on voltage is much different from normal diodes. However, they still have a depletion layer and capacitance. As extra credit measure the red, yellow and green LEDs supplied in the Analog Parts Kits as you did the normal diodes. Be sure to insert the LEDs into the test setup with the proper polarity for reverse bias. If you did it wrong you will probably see the LED light up at some point. Include your calculations, a table and plot of your measured capacitance vs. voltage for each LED in your lab report.+Light emitting diodes or LEDs are also PN junctions. They are fabricated from materials other than Silicon so their turn on voltage is much different from normal diodes. However, they still have a depletion layer and capacitance. As extra credit measure the red, yellow and green LEDs supplied in the ADALP2000 Analog Parts Kits as you did the normal diodes. Be sure to insert the LEDs into the test setup with the proper polarity for reverse bias. If you did it wrong you will probably see the LED light up at some point. Include your calculations, a table and plot of your measured capacitance vs. voltage for each LED in your lab report.
  
 ===== Advanced Credit measurements: ===== ===== Advanced Credit measurements: =====
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 Include your calculations, a table and plot of your measured capacitance vs. voltage for each transistor in your lab report. Compare your measured C-B capacitance to the manufacturer's data sheet for these transistors. Note, data sheets don't often list the C-B capacitance directly. It is often included as part of the output capacitance or something similar. Include your calculations, a table and plot of your measured capacitance vs. voltage for each transistor in your lab report. Compare your measured C-B capacitance to the manufacturer's data sheet for these transistors. Note, data sheets don't often list the C-B capacitance directly. It is often included as part of the output capacitance or something similar.
 +
 +<WRAP round download>
 +** Lab Resources **
 +  * Fritzing files: [[downgit>education_tools/tree/master/m2k/fritzing/volt_dep_cap_pn_junc_bb | v_dep_pn_bb]]
 +  * LTSpice files: [[downgit>education_tools/tree/master/m2k/ltspice/v_dep_pn_ltspice | v_dep_pn_ltspice]]
 +</WRAP>
  
 ==== For Further Reading: ==== ==== For Further Reading: ====
-[[http://en.wikipedia.org/wiki/Varicap|The Varactor Diode, Varicaps]]+[[wp>Varicap|The Varactor Diode, Varicaps]]
  
 **Return to the Lab Activity [[university:courses:electronics:labs|Table of Contents]]** **Return to the Lab Activity [[university:courses:electronics:labs|Table of Contents]]**
  
- +  
university/courses/electronics/electronics-lab-pn-junction-cap.1490280218.txt.gz · Last modified: 23 Mar 2017 15:43 by Doug Mercer

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