B EE 331 Lab 1 – Diode Characterization - Su23

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B EE 331 Devices and Circuits I Lab 1 – Diode Characterization Rev. 2023 1/15 Lab 1 – Diode Characterization Introduction The objectives for the lab are: • Learn various methods for characterizing diodes. • Understand and observe the nonlinear 𝑪?𝒓𝒓𝒆?? - 𝑽?𝒍?𝒂𝒈𝒆 ( 𝑰 - 𝑽 ) characteristics of various types of diodes. • Explore the “Forward Bias” characteristics of standard semiconductor diodes • Explore the “Reverse Bias” characteristics of Zener diodes . • Learn to use LTSPICE in simulating individual diode characteristics. • Learn how to plot I-V curve Lab 1 has three components. Assess Method Experiment Topic Time allotted Grading point Team Lab 1 - 0 LT Spice Simulation of diode I-V characteristics 2 hours 20 Team Lab 1 - 1 Measuring diode forward I- V Characteristic 1 hour 40 Team Lab 1 - 2 Measuring Zener Diode I-V Characteristics 1 hour 40 Suggestions: • Prioritize Lab 1-1 and Lab 1-2 for in-person lab sessions • Conduct Lab 1-0 in-person or at home

B EE 331 Devices and Circuits I Lab 1 – Diode Characterization Rev. 2023 2/15 Lab 1-0: LTSpice Simulation of Diode Characterization Reading Assignment Until now we have studied linear circuit components such as resistors, capacitors, and inductors. Linear components have a linear current-versus-voltage relationship. If you double the voltage across the component, the current doubles. Now we will look at our first nonlinear component, the diode. The diode is a two terminal device consisting of an anode (arrow) and a cathode (bar) such as the circuit schematic representation, and picture of an 1N4148 diode shows in Figure 1. In the picture, a black ring is used to mark the cathode (bar) of the diode. The polarity of a diode can be tested with a digital multimeter (DMM) in its diode setting. Touch each probe of the DMM voltage terminals across the diode and note the reading. If the display indicates a positive value (i.e. +0.7 V), then the positive probe is touching the anode, and negative probe is touching the cathode. Figure 1 − The diode schematic symbol with polarity and a 1N4148 silicon diode. A textbook diode has a nonlinear current-versus-voltage relationship (also called an 𝑰-𝑽 curve) such as the one shown below in Figure 2. The diode has two major regions of operation known as the forward and reverse bias regions. In the forward-bias region a positive voltage is applied to the anode (arrow) side of diode. When the voltage exceeds a threshold ( V TH ~ 0.7 V in Figure 2), current conducts through the diode in the direction of the arrow. In the reverse-bias region, a negative voltage is applied across the anode to cathode. In the reverse-bias region, the diode conducts no current (or very little leakage current) until a breakdown voltage is reached. Figure 2 − Diode I-V characteristics.

B EE 331 Devices and Circuits I Lab 1 – Diode Characterization Rev. 2023 3/15 • In Lab 1-1 we will measure the Forward I-V characteristic curve of several typical semiconductor diodes ( 1N4148 silicon diode and the small signal 1N5711 Schottky diodes) that are used for rectification and small signal modulation/demodulation/mixing circuits respectively. • In Lab 1-2 we will measure the Forward/reverse I-V characteristic curve of Zener diodes 1N4732 and 1N4744 . LTSpice Simulations of Diode Circuits Introduction SPICE simulations can be used to plot I-V characteristics of individual diodes. In these prelab we prefer to use the LTS pice simulator available for MAC’s or PC’s as a free software download at www.analog.com . However, any SPICE simulator of the student’s choice is equally applicable. We will learn how to use a DC Sweep operation in LTSpice to obtain an I-V characteristic curve for an individual diode. Procedure for LTSpice Simulations of Diode 𝑰 - 𝑽 Characteristics (1) Open the LTS pice simulator and “build” the LT Spice circuit shown in Figure 3 with the step-by- step procedure given below. Figure 3 – LTSpice Diode Curve Tracer Schematic (2) In the toolbar at the top of the screen select the diode symbol. Place it in the schematic. Right click on the diode symbol and a dialog box will appear ( Diode – D1 ). Select: Pick New Diode , and the dialog box ( Select Diode ) will appear. Find the 1N4148 diode and select it. (3) Now, as shown in the schematic, connect a voltage source and a 500 Ω resistor to the anode of the diode. Ground the cathode of the diode and the voltage source. Label the voltage at the voltage source, IN and the output voltage diode . Right click on the voltage source and a dialog box ( Voltage Source V1 ) will appear. Set DC value[V] to 0. (4) Run the simulation. Select DC Sweep and a dialog box ( Edit Simulation Command ) will appear as shown below in Figure 4. Enter the quantities shown in Figure 5 and click OK.

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B EE 331 Devices and Circuits I Lab 1 – Diode Characterization Rev. 2023 4/15 Figure 4 – Edit Simulation Command (5) A blank plot window will appear after the simulation has run. Add traces by right clicking in the plot window and selecting Add Traces . A dialog box ( Add Traces to Plot ) will appear. Select I(R1) since R1 is the resistor in series with the forward biased diode. A plot of the series current versus the V1 voltage sweep should appear. (6) Now we will show how to format this plot for cutting and pasting into a Lab Report. Points will be subtracted in lab reports where plots are not given with white backgrounds, visible waveform widths, legible axis, gridlines and labels . To change the color of the background to white, select Tools in the plot window toolbar and then select Color Preferences . A dialog box ( Color Palette Editor ) will appear and select; Item Background Selected Item Color Mix: All the colors to 255 (7) To make the traces thicker, select Tools in the plot window toolbar and then select Control Panel . A dialog box ( Control Panel ) will appear and select Waveforms , Data Trace Width = 3. The plot output of I(R1) versus V1 should look like Figure 5.

B EE 331 Devices and Circuits I Lab 1 – Diode Characterization Rev. 2023 5/15 Figure 5 – LTSpice DC Sweep (8) To plot the diode current I(R1) versus the diode voltage V(diode) on the horizontal axis (like an I-V characteristic on an x-y instrument display) move the cursor over the horizontal axis until a ruler appears. Right click and a dialog box ( Plot Limits ) appears. Enter the Quantity Plotted: V(diode) . (9) To set the horizontal and vertical axis, select Plot Settings in the plot window toolbar and then select Manual Limits . A dialog box will appear ( Plot Limits ) and set the limits to the values shown below; Vertical Axis Top: 20mA Tick: 1mA Bottom: 0mA Horizontal Axis Left: 0V Tick: 50mV Right: 750mV The plot should now appear as given in Figure 6 below.

B EE 331 Devices and Circuits I Lab 1 – Diode Characterization Rev. 2023 6/15 Figure 6 – LTSpice Output Diode Current versus Diode Voltage for 1N4148 (10) Now the student can further format and annotate this plot if it is asked for in the Lab Report. One can then copy a screenshot of the output by choosing Copy bitmap to Clipboard under Tools in the toolbar. This bitmap screenshot can then be pasted directly into a Lab Report if asked for. However, in this lab we will export the simulated data and plot our LTSpice simulations along with measured data in the same Excel plot. Therefore, we will discuss how to do this next (11) To export the data into a text file (an ASCII text file that can be read by any text editor or Excel spreadsheet), we can choose Export Data as Text under the File toolbar. When the dialog box ( Select Traces to Export ) appears, hold the control key and select V(diode) and I(R1) before clicking OK . In File , enter the name 1N4148 SPICE.txt. Now it can be opened in Excel and plotted along with the measured data. (12) Repeat this procedure for generating LTspice simulation data for the 1N5711 Schottky diode. 2.2 LTspice Simulations of Zener Diode Circuits (1) Repeat procedure for generating LTSpice simulation data for the 1N4732 Zener diode. Note: These diodes are not supplied with LTSpice, therefore you will have to download a SPICE model from the web and set it up in your LTSpice simulator . Manufacturers typically supply these SPICE models, which include the parameters for the diode. Read and research the LTSpice manual on how to do this. (2) For Zener diode, please simulate for voltages -5 V to 1V so that the I-V curve shows both the reverse breakdown and forward bias.

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B EE 331 Devices and Circuits I Lab 1 – Diode Characterization Rev. 2023 7/15 Lab 1-1 Measuring Standard Diode Forward 𝑰 - 𝑽 Characteristic 1.0 Objective The objective of this lab is to measure the forward bias 𝐼𝑉 characteristics of standard semiconductor diodes. In this lab we will investigate the characteristics of the 1N4148 Silicon diode, and the 1N5711 Schottky diode. We will obtain and plot the forward voltage drops. This data will be compared to the values given by the manufacturer datasheets for each diode. In Figure 1, a black ring is used to mark the cathode (bar) of the diode. The polarity of a diode can be tested with a digital multimeter (DMM) in its diode setting. Touch each probe of the DMM voltage terminals across the diode and note the reading. If the display indicates a positive value (i.e. +0.7 V), then the positive probe is touching the anode, and negative probe is touching the cathode. Figure 1 − The diode schematic symbol with polarity and a 1N4148 silicon diode. 1.1 Procedure for Measuring Diode Forward 𝑰 - 𝑽 Characteristics 1.1.1 Prior to building the circuit, measure the values of the chosen resistors ( 𝑅 = 10KΩ, 1KΩ, and 100 Ω ) with an Ohmmeter and record them in Table 1 below. 1.1.2 Build the circuit as shown as shown in Figure 2, the Forward Bias Diode Test Circuit. The circuit consists of a DC power supply across a resistor and forward biased 1N4148 diode in series. Use the previous measurement of the diode polarity, to make sure that the diode is forward biased. Three different values ( 𝑅 = 10KΩ, 1KΩ, and 100 Ω ) of resistors will be used in this measurement technique.

B EE 331 Devices and Circuits I Lab 1 – Diode Characterization Rev. 2023 8/15 Figure 2 − Forward bias diode test circuit. 1.1.3 Record the diode current (measured by the power supply current meter). Use the DMM voltmeter to measure the voltage across the resistor and the diode. This can be done by fixing the negative terminal of the voltmeter to a common point between the resistor and diode, then alternating the positive terminal to measure the voltage drop across the resistor or diode. Keep in mind that the voltage measured across the diode with the voltmeter using this technique is the negative of the voltage entered into the table. If you are using the voltmeters contained in the Analog Discovery modules, you can setup the two channels (Voltmeter CH1 and CH2 simultaneously). Enter these values along with the power supply voltage (V DC-supply ) with four digits of precision in Table 1 . Data can be entered into your Lab Notebook and then later an Excel spreadsheet containing these data tables. This data table is to be included in the Lab Report Appendix . Plot these discrete data points in the main Report using Excel. 1.1.4 Calculate the current through the circuit using Ohm’s law for the resistor and record this value in Table 1 and your Excel spreadsheet. It is now possible to plot the current (I Diode ) through the diode as a function of the voltage (V Diode ) across the diode (forward I-V characteristic). This calculation can be done outside the lab hour. 1.1.5 Repeat this experiment for the 1N5711 Schottky diode and record the values in your Lab Notebook and your Excel data files.

B EE 331 Devices and Circuits I Lab 1 – Diode Characterization Rev. 2023 9/15 Table 1. Measuring diode forward bias I-V characteristics Setting parameters Measurements 1N4148 Diode Resistors (Ω) V DC-Supply (Volts) Diode current, I Diode (mA) V R (Volts) V Diode (Volts) Calculated diode current = 𝑉 ? 𝑚?𝑎?𝑢??? 𝑅 (𝑚𝐴) Measured R = for a 10 kΩ resistor 0 0.5 0.6 0.7 0.8 0.9 1 2 3 4 5 Measured R = for a 1 kΩ resistor 0 0.5 0.6 0.7 0.8 0.9 1 2 3 4 5 Measured R = for a 100 Ω resistor 0 0.5 0.6 0.7 0.8 0.9 1 2 3 4 5

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B EE 331 Devices and Circuits I Lab 1 – Diode Characterization Rev. 2023 10/15 Lab 1-2 Measuring Zener Diode reverse 𝑰 - 𝑽 Characteristic 2.0 Objective The objective of this lab is to measure the reverse bias 𝐼𝑉 characteristics of Zener diodes. In this lab we will investigate the characteristics of the 1N4632 Zener diode. We will obtain and plot the reverse voltage drops. This data will be compared to the values given by the manufacturer datasheets for each diode. In this experiment we will measure the reverse I-V characteristic curves of two Zener diodes ( 1N4732 and 1N4744 ) that are used for voltage regulation. The procedure for taking data in lab 1-2 is the same as in 1-1 with exception of the Zener diodes being measured in the reverse bias direction. The voltage and current will be negative since Zener diodes operate in the reverse region (see Figure 3). Warning: Care must be taken not to increase the voltage (hence the current) suddenly as this might damage the diode. 2.1 Procedure for Measuring Diode Reverse 𝑰 - 𝑽 Characteristics 2.1.1 Prior to building the circuit, measure the values of the chosen resistors ( 𝑅 = 10KΩ, 1KΩ, and 100 Ω ) with an Ohmmeter and record them in Table 2 below. 2.1.2 Build the circuit as shown as shown in Figure 3, the Reverse Bias Zener Diode Test Circuit. The circuit consists of a DC power supply across a resistor and reverse biased 1N4632 Zener diode in series. Use the previous measurement of the diode polarity, to make sure that the diode is reverse biased. Three different values ( 𝑅 = 10KΩ, 1KΩ, and 100 Ω ) of resistors will be used in this measurement technique. Figure 3 – Reverse bias Zener diode test circuit. R v Z + - v DC A V Bench power supply DMM Power supply current meter R V DMM

B EE 331 Devices and Circuits I Lab 1 – Diode Characterization Rev. 2023 11/15 2.1.3 Record the diode current (measured by the power supply current meter). Use the DMM voltmeter to measure the voltage across the resistor and the diode. This can be done by fixing the negative terminal of the voltmeter to a common point between the resistor and diode, then alternating the positive terminal to measure the voltage drop across the resistor or diode. In this case the voltage across the diode measured on the voltmeter will be negative with correct polarity. If you are using the voltmeters contained in the Analog Discovery modules, you can setup the two channels (Voltmeter CH1 and CH2 simultaneously). Enter these values along with the power supply voltage (V DC-supply ) with four digits of precision in Table 2 of your Lab Notebook . Create an Excel spreadsheet containing these data tables which can be used to plot the data. 2.1.4 Calculate the current through the circuit using Ohm’s law for the resistor and record this value in the data table and Excel spreadsheet. It is now possible to plot the current through the diode as a function of the voltage applied (measured) across the diode (reverse I-V characteristic).

B EE 331 Devices and Circuits I Lab 1 – Diode Characterization Rev. 2023 12/15 Table 2. Measuring Zener Diode reverse-bias I-V characteristics Setting parameters Measurements 1N4732 Diode Resistors (Ω) V DC-Supply (Volts) Diode current, I Diode (mA) V R (Volts) V Diode (Volts) Calculated diode current = 𝑉 ? 𝑚?𝑎?𝑢??? 𝑅 (𝑚𝐴) Measured R = for a 10 kΩ resistor 0 1.0 1.5 1.6 1.7 1.8 1.9 2.0 3.0 3.5 0.25 Measured R = for a 1 kΩ resistor 0 1.0 1.5 1.6 1.7 1.8 1.9 2.0 3.0 3.5 0.25 Measured R = for a 100 Ω resistor 0 1.0 1.5 1.6 1.7 1.8 1.9 2.0 3.0 3.5 0.25

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B EE 331 Devices and Circuits I Lab 1 – Diode Characterization Rev. 2023 13/15 Lab Report Guideline 3 Lab 1-1 Report for both 1-1 and 1-2 3.1 Download the Lab Report Template and finish your Lab 1 using the template as guidance. 3.2 In your Objective section of the report, state the objective of this lab. 3.3 In the Procedure section give a short synopsis of the procedure taken and include a simplified schematic (you may use your LTspice schematic here) showing the measurement technique. Do not copy the procedure given in this Lab Manual. Instead write your own single short paragraph description of the procedure. Copied manual will be considered as a misconduct. Place a photograph of your circuit here. 3.4 In the Discussion of Measurements and Results plot the diode current versus diode voltage discrete data points in Excel obtained for three different resistors on the same plot. Do this for both 1N4148 and 1N5819 didoes. Identify the diode voltage drop in the middle of the linear region of the I-V curve for each diode. • Are those I-V curves matched for three resistors? If not, explain why the same diode exhibits different I-V curves and justify which one you want to use. 3.5 Generate the current versus voltage (I-V) characteristic (in Excel) of a silicon diode using the diode equation from the textbook. 𝐼 𝐷 = 𝐼 ? (? 𝑣 𝐷 𝑉 𝑇 ⁄ − 1) • You can find I s from your measured data by plotting them in semi-log scale (ln(I D ) vs V D ). • Use V T = 25.9mV. In your plot, compare the theoretical I-V curve to experimental I-V data points of the 1N4148 and the 1N5711 diodes. Comment on the differences between the results. 3.6 Also in the Discussion of Measurements and Results plot the diode current versus diode voltage from LTSpice simulations and measured data points in Excel for two forward biased diodes ( 1N4148 Silicon and 1N5711 Schottky). Each diode should be plotted on a separate plot along with a short discussion on LTSpice simulations and measurements. Any data used from a m anufacturer’s datasheet should be highlighted and stapled to the Appendix at the end of the Lab 1 Report. Only attach the page of the datasheet of the information that was used, not the entire datasheet. 3.7 In your Summary and Conclusions section give short summary of the differences between the two diodes and compare their experimental characteristics versus their data given in the manufacturer datasheets. • Describe how you find the reverse saturation current (I S ) of the diode and show the values for 1N4148 and 1N5819. • Comment on the differences between the LTSpice simulations and the measured data. In forward biased 1N4148 and 1N5711 diodes, compare the measured forward bias resistance (diode voltage-drop in the middle of the linear region of the forward I-V curve) to the LTSpice derived values.

B EE 331 Devices and Circuits I Lab 1 – Diode Characterization Rev. 2023 14/15 3.8 Give two different applications of these diodes. Briefly explain how the diode circuits operate in those applications. 4 Lab1-2 Report 4.1 In your Objective section of the report, state the objective of this lab. 4.2 In the Procedure section give a short synopsis of the procedure taken and include a simplified schematic (you may use your LTSpice schematic here) showing the measurement technique. Do not copy the procedure given in this Lab Manual. Instead write your own single short paragraph description of the procedure. Copied manual will be considered as a misconduct. Place a photograph of your circuit here. 4.3 In the Discussion of Measurements and Results plot the diode current (negative polarity) versus diode voltage (negative polarity) data points in Excel for the two Zener diodes on the same plot. Identify the Zener voltages 𝑉 𝑧 and the equivalent series resistance ? 𝑧 from the plots shown below in Figure 4. Figure 4 – Operation in the Zener diode breakdown region. • In the reverse biased 1N4732 Zener diode, compare the Zener voltages 𝑉 𝑧 and the equivalent series resistance ? 𝑧 as calculated from the measured data and LTspice simulations. • In the reverse biased 1N4732 Zener diode, compare the Zener voltages 𝑉 𝑧 from the measured data and manufacturer data sheet. • What is the main application of the Zener diode? Briefly explain how the Zener diodes operate in those applications. 5 Simulation Report • Individual simulation report must be attached. Mark your name in the report

B EE 331 Devices and Circuits I Lab 1 – Diode Characterization Rev. 2023 15/15 Appendix: lab kit components This is based on the DigiKey order form from Dr KT Kim. Part number # Description How to identify notes semiconductors BAT 85 2 Schottky diode Small, transparent Unreadable 2 Schottky diode Small, transparent 1N4148 4 Diode Small, transparent Lab 1, Lab 2 1N4732 2 4.7v Zener diode Medium, transparent Lab 1 1N4744 1 15v Zener diode Medium, transparent Lab 1 1N5711 2 Schottky diode Medium, blue Lab 1 2N3904 2 NPN BJT transistor TO-92 (3-pin) Lab 4 2N7000 2 NMOS transistor TO-92 (3 pin) Lab 3 CD4007 2 CMOS transistors 14-pin DIP Lab 3 LM741 2 Op amp 8-pin DIP package optional inductor 107C 1 100mH inductor Large black cylinder optional capacitor 1 30 uF cap Small black cylinder 2 10 uF Small black cylinder 2 100nF cap Small axial resistor 1 49.5 ohm 1 100 ohm 1 200 ohm 1 498 ohm 5 1.0K 1 1.3K 1 1.7K 2 10K 1 24.5K 1 44K 1 100K 1 106K

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