Lab 2: Diode Characteristics and Diode Circuits

1. Learning Outcomes Lab 2: Diode Characteristics and Diode Circuits At the end of this lab, the students should be able to compare the experimental data to the theoretical curve of the diodes. The students use the Analog Discovery Module and WaveForms software to plot the I-V characteristics of the diodes. The students also construct rectifier and filter circuits using diodes and capacitors. 2. Health and Safety Any laboratory environment may contain conditions that are potentially hazardous to a person s health if not handled appropriately. The Electrical Engineering laboratories obviously have electrical potentials that may be lethal and must be treated with respect. In addition, there are also mechanical hazards, particularly when dealing with rotating machines, and chemical hazards because of the materials used in various components. Our LEARNING OUTCOME is to educate all laboratory users to be able to handle laboratory materials and situations safely and thereby ensure a safe and healthy experience for all. Watch for posted information in and around the laboratories, and on the class web site. 3. Lab Report Students work in groups of 2 with laboratories being on alternative week (in 2C80/82). Each student must have a lab book for the labs. The lab book is used for lab preparation, notes, record, and lab reports. The lab books must be handed before 5:00 pm on the due date (same day of the following week) into the box labeled for your section across from 2C94. The lab books are marked and returned before the next lab. 4. Background The simplest and most fundamental nonlinear circuit element is the diode. The diode is a device formed from a junction of n-type and p-type semiconductor material, shown in Figure 4-1a. The lead connected to the p-type material is called the anode and the lead connected to the n-type material is the cathode, shown in Figure 4-1b. In general, the cathode of a diode is marked by a solid line on the diode package, shown in Figure 4-1c. Figure 4-1: (a) PN-junction model, (b) schematic symbol, and (c) physical part for a diode One of the primary functions of the diode is rectification. When it is forward biased (the higher potential is connected to the anode lead), it will pass current. When it is reverse biased (the higher potential is connected to the cathode lead), the current is blocked. The characteristic I-V curve of a real diode is shown in Figure 4-2. Rev A Copyright 2016 University of Saskatchewan Page 1 of 15

5. Material and Equipment Figure 4-2: I-V Curve for a Real Diode Material (supplied by department) 1N4005 (rectifier diode) EK04 (Schottky barrier diode) 1N4733 (Zener diode) Equipment (supplied by student) Analog Discovery Module Waveforms software Breadboard and wiring kit C566C-RFS-CT0W0BB2 (red LED) Resistors: 1 x 1 kω, 1 x 100 Ω Capacitors: 1 x 10 uf Rev A Copyright 2016 University of Saskatchewan Page 2 of 15

6. Prelab 1. For each of: 1.1. 1N4005 (rectifier diode) 1.2. EK04 (Schottky barrier diode) 1.3. 1N4733 (Zener diode) 1.4. C566C-RFS-CT0W0BB2 (red LED) Look up the characteristics of each device by doing a web search. Fill in following table for each of the devices: Rating/Characteristic Forward Voltage Forward Current (sustained) Peak Forward Current (surge) Peak Reverse Voltage Maximum Reverse Current Maximum Average Power Dissipation Value 2. A SPICE circuit file for a 1N4005 rectifier diode is given in Figure 6-1. Using LTspice (a guide to using LTspice can be found in Laboratory #1 Appendix A), include a screen capture of the plot of the I-V characteristics of the diode in your lab report (i.e. add trace I(D1) ). It should look similar to Figure 6-2. 1N4005 Circuit ** 1N4005 Model.MODEL DI_1N4005 D ( IS=76.9p RS=42.0m BV=600 IBV=5.00u + CJO=26.5p M=0.333 N=1.4 TT=4.32u ) ** Circuit Vin 1 0 D1 1 0 DI_1N4005 ** Analysis.DC Vin 0 1 0.01 ; Voltage across diode ; Diode ; Sweep input voltage.end Figure 6-1: 1N4005 SPICE Circuit File Rev A Copyright 2016 University of Saskatchewan Page 3 of 15

Figure 6-2: Example LTspice Output 3. For the circuit shown in Figure 7-8, a SPICE circuit file representing the circuit is given in Figure 7-8. Use LTspice to plot Vin and Vout and include a screen shot of the plot in your lab report. Do the waveforms look as you expected for a half-wave rectifier (give the reasoning behind your answer)? Half-Wave Rectifier Circuit ** 1N4005 Model.MODEL DI_1N4005 D ( IS=76.9p RS=42.0m BV=600 IBV=5.00u + CJO=26.5p M=0.333 N=1.4 TT=4.32u ) ** Circuit V1 Vin 0 SIN(0 2 60) D1 Vin Vout DI_1N4005 R1 Vout 0 1kOhm ; Vin 60 Hz 2 V Sinusoidal Voltage Source ; D1 1N4005 Rectifier Diode ; R1 1 kohm Resistor ** Analysis.TRAN 1ms 40ms.end Figure 6-3: Half-Wave Rectifier SPICE Circuit File Rev A Copyright 2016 University of Saskatchewan Page 4 of 15

4. Add Capacitor C1 (10 µf) to the SPICE circuit file shown in Figure 6-3 so that it models the circuit shown in Figure 7-10. Use LTspice to plot Vin and Vout and include a screen shot of the plot in your lab report. Do the waveforms look as you expected for a half-wave rectifier with a capacitor (give the reasoning behind your answer)? Help with SPICE format can be found at: http://www.eecg.toronto.edu/~kphang/teaching/spice/ 5. Change the value of Capacitor C1 in Step 4 to 100 µf. Use LTspice to plot Vin and Vout and include a screen shot of the plot in your lab report. Comment on how the output voltage is different than that observed in Step 4 and explain why they are different (beyond just that the value of the capacitor has changed). Rev A Copyright 2016 University of Saskatchewan Page 5 of 15

7. Lab Procedures Debugging (or What To Try When Things Aren't Working) There are a number of things/procedures you should use to debugging circuits when things are not working correctly. These include (but are not limited to): Check that all component pins are correctly inserted in the breadboard (sometimes they get bent underneath a component). Make sure that components are not "misaligned" in the breadboard (e.g. off by one row). Double check component values (you can measure resistors, capacitors, and inductors). Try a different section in the breadboard (in case there is a bad internal connection). Measure the source voltages to verify power input. Measure key points in the circuit for proper voltage/waveform (i.e. divide-and-conquer). 1N4005 Forward Bias I-V Characteristics 1. Construct the circuit shown in Figure 7-1 on your breadboard: 1.1. Use Wavegen Channel 1 (W1, yellow wire, see Appendix A) to generate "Vin". Set to a 10 Hz 0 4 V "triangle" waveform (i.e. Amplitude = 2 V, Offset = 2 V). Remember to click "Run" to start the output from Wavegen. R1 100 Ω Vin D1 1N4005 Figure 7-1: 1N4005 Circuit Schematic 2. Connect "Channel 1" (1+ and 1-) to measure the input voltage V in. 3. Connect "Channel 2" (2+ and 2-) to measure the voltage across the diode (V D1). 4. Open the Scope tool, and hit Scan. Adjust its parameters to: 4.1. Trigger Level = 1 V 4.2. Time Base = 20 ms/div 4.3. Channel 1 Range = 1 V/div 4.4. Channel 2 Range = 200 mv/div Rev A Copyright 2016 University of Saskatchewan Page 6 of 15

5. If your circuit is working correctly, you should see something similar to Figure 7-2. The example shown is using the Analog color: Light option in Settings Options that utilizes a white background which should use less resources when printing. Figure 7-2: 1N4005 Oscilloscope Window 6. To determine the current through the diode, we can measure the voltage across resistor R1, and then using Ohm's law, simply divide this voltage by the resistance value of R1 (i.e. 100 Ω) to get the current value I D1. Rather than moving Channel 1 or Channel 2 to measure V R1, we can recognize that V R1 can be found by (V in V D1): 6.1. Click on Add Channel and select Custom" (see Figure 7-3). 6.2. Click on the bottom field of Math 1 (highlighted in red in Figure 7-4) to bring up the configuration dialog shown in Figure 7-5. 6.3. Enter (C1 C2) / 100 in the top field. This is the calculation of current running through R1 (and as R1 and D1 are in series, D1 as well). Set the Units to A (Amperes). 6.4. Change the Range on Math 1 to 10 ma/div and the Scope window should look similar to Figure 7-6. Rev A Copyright 2016 University of Saskatchewan Page 7 of 15

Figure 7-5: Math Channel Configuration Figure 7-6: Scope with Current Waveform 7. Use "View Add XY" to show a graph of the diode I-V characteristic (set "X: C2" and "Y: M1"). 8. Adjust "Time", "Channel 1", "Channel 2", and "Math 1" to get a better view of the waveforms (example shown in Figure 7-7, set to Analog color: Light in Settings Options, may be less resources to print). Include a screen capture of the Scope window in your lab submission. Rev A Copyright 2016 University of Saskatchewan Page 9 of 15

Figure 7-7: Scope Window with 1N4005 I-V Characteristic 9. REQUIRED: Demonstrate to a lab instructor and make sure your demonstration is recorded by the lab instructor (only required for 1N4005). 10. Study the I-V curve carefully and fill in the following table with appropriate values (go to full screen to be see the graph better). You can either try and read it off of the XY plot, or use the X cursor in the main window (ask a lab instructor if you are unsure of how to do this). Document the "knee" voltage of this diode in your report. Diode Voltage (V) Diode Current (A) Characteristic 0 0 One of "Off", "Just turning on", "Fully on" Every 50 mv until max Rev A Copyright 2016 University of Saskatchewan Page 10 of 15

EK04 Forward Bias I-V Characteristics Repeat Section 7.2 but replace the 1N4005 diode with an EK04 Schottky Barrier diode. 1N4733 Forward Bias I-V Characteristics Repeat Section 7.2 but replace the 1N4005 diode with a 1N4733 Zener diode. LED Forward Bias I-V Characteristics Repeat Section 7.2 but replace the 1N4005 diode with a C566C-RFS-CT0W0BB2 Red LED. Comparison of I-V Characteristics Graph all four I-V characteristics (sections 7.2 to 7.5) on the same graph so you can compare the I-V characteristics. Half-Wave Rectifier 1. Construct the circuit shown in Figure 7-8 on your breadboard: 1.1. Use Wavegen Channel 1 (W1) to generate "Vin". Set to a 60 Hz 4 V p-p "sine wave" (i.e. Amplitude = 2 V, Offset = 0 V). Remember to click "Run" to start the output from Wavegen. D1 1N4005 + Vin R1 1 kω Vout _ Figure 7-8: Half-Wave Rectifier Schematic 2. Connect "Channel 1" (1+ and 1-) to measure the input voltage V IN. 3. Connect "Channel 2" (2+ and 2-) to measure the output voltage V OUT. 4. Open the Scope tool and select Run. Set Time Base to 5 ms/div. Add measurements for "C1 Frequency", "C1 Maximum", "C2 Maximum", and "C2 Minimum". You should see something similar to Figure 7-9. 5. Include a screen shot of the Scope window with the waveforms in your lab submission. Label the peak voltages of the waveforms. Explain the amplitude and time differences between V IN and V OUT. Rev A Copyright 2016 University of Saskatchewan Page 11 of 15

Half-Wave Rectifier with Capacitor Figure 7-9: Half-Wave Rectifier Waveforms 1. Add a 10 uf Capacitor in parallel to Resistor R1 from section 7.5 (resulting in the circuit shown in Figure 7-10). If you are using a "polarized" capacitor (usually indicated by having a "+" and/or "-" signs on the capacitor), make sure the capacitor is inserted correctly. D1 1N4005 + Vin R1 1 kω C1 10 µf Vout _ Figure 7-10: Half-Wave Rectifier with Capacitor Schematic 2. Include a screen shot of the Scope window with the waveforms in your lab submission. 3. REQUIRED: Demonstrate to a lab instructor and make sure your demonstration is recorded by the lab instructor. 4. Calculate the theoretical ripple voltage using information from the text book and compare it to the experimental result. Rev A Copyright 2016 University of Saskatchewan Page 12 of 15

Zener Diode Characteristics The Zener diode has the unique property of maintaining a desired reverse biased voltage. This makes it useful in voltage regulation. In this exercise, you are to tabulate the regulating properties of the Zener diode. 1. Construct the circuit shown in Figure 7-11 on your breadboard: 1.1. Make sure to insert the diode with its Cathode (indicated by the "bar") facing Resistor R1. R1 100 Ω + Vin D1 1N4733 Vdiode _ Figure 7-11: Zener Diode Circuit Schematic 2. Measure the Zener diode properties by varying the input voltage and measuring the voltage across the diode and the current through the diode. Fill in the following table when you measure the voltage and current. Document in your lab book how you connected the circuit to have the input voltage go up to 7V from the Analog Discovery. Regulating means that the output voltage (Vdiode) is basically a constant value, independent of the input voltage Vin. 3. Include a screen capture of the Scope window with the appropriate waveforms to show how you obtained the values for the table. Supply Voltage Vin (V) 3.0 4.0 4.5 5.0 5.5 6.0 6.5 7.0 Diode Voltage (V) Diode Current (A) Regulating (Yes/No) Rev A Copyright 2016 University of Saskatchewan Page 13 of 15