Electronics I - Laboratory 1
Diode I/V Characteristics
I. Objectives
1.
2.
3.
4.
Develop I/V characteristics of a silicon diode.
Develop I/V characteristics of a germanium diode.
Develop I/V characteristics of a light emitting diode (LED).
Utilize a current limiting resistor to power a LED from a voltage source.
II. Pre-Lab Requirements
1. None
III. Laboratory Requirements
1. Required Parts and Equipment
A.
B.
C.
D.
E.
F.
G.
H.
DC power supply.
One bench DMM
2 - Fluke hand-held DMMs
1 - Proto-Board (PB-103)
1 – 1N4148 silicon diode
1- 1N34A germanium diode
1- Red LED
Resistors of the following values:
#
1
1
Value
220 Ω
1000 Ω
I. Wires and leads for circuit connections.
2. Required Information
A. Diode Pin Out Orientation
The diodes used for this experiment and their respective pin-out orientations are
shown in Figure 1 below. Generally diodes are marked with a colored band that
denotes the negative pin. For LEDs the pins are usually different lengths with the
short pin being negative; however, on the LEDs that you will be using the pins are
the same length. The negative pin on the LEDs is connected to the larger internal
structure.
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Figure 1. Diode I/V Test Circuit
B. Diode Data Sheets
The diode data sheets may be found at the following web sites:
IN4148 – http://www.nxp.com/documents/data_sheet/1N4148_1N4448.pdf
IN34A - http://www.circuitspecialists.com/products/pdf/1n34a.pdf
3. Laboratory Procedure
A. Silicon Diode I/V Characteristics
In Experiment 1, a 1N4148 silicon diode will be tested to produce voltage and
current data that will be used to plot the I/V characteristic curve of the diode. To
produce the data, a test circuit will be constructed using the PB-103 Proto-Board.
The test circuit will be powered by a DC power supply. Test equipment (TE)
consisting of DMMs will be used to measure the following parameters:
Circuit input voltage (Vin)
Voltage drop across the diode (Vd)
Current through the diode (Id).
Experiment 1 – Measuring the I/V Characteristics of a Silicon Diode.
1. Construct the circuit shown in Figure 2. Utilize the Keithley DMM to measure the
current flowing through the diode (Id), a Fluke DMM to measure the voltage drop
across the diode (Vd), and a Fluke DMM to measure the voltage input (Vin) to the
circuit.
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Figure 2. Diode I/V Test Circuit
2. Take data samples between Vd = -2V and Vd = 1V. Collect 4 evenly spaced
samples between -2V and 0V and 10 evenly spaced samples between 0V and 1 V.
Make sure you do not exceed the wattage rating for the diode
B. Germanium Diode I/V Characteristics
In Experiment 2, a 1N34A germanium diode will be tested to produce voltage and
current data that will be used to plot the I/V characteristic curve of the diode. To
produce the data, a test circuit will be constructed using the PB-103 Proto-Board.
The test circuit will be powered by a DC power supply. Test equipment (TE)
consisting of DMMs will be used to measure the following parameters:
Circuit input voltage (Vin)
Voltage drop across the diode (Vd)
Current through the diode (Id).
Experiment 2 – Measuring the I/V Characteristics of a Germanium Diode.
1. Construct the circuit shown in Figure 2. Utilize the Keithley DMM to measure the
current flowing through the diode (Id), a Fluke DMM to measure the voltage drop
across the diode (Vd), and a Fluke DMM to measure the voltage input (Vin) to the
circuit.
2. Take data samples between Vd = -2V and Vd = 0.75V. Collect 4 evenly spaced
samples between -2V and 0V and 10 evenly spaced samples between 0V and 0.75
V. Make sure you do not exceed the current rating for the diode.
B. Light Emitting Diode I/V Characteristics
In Experiment 3, a LED will be tested to produce voltage and current data that will
be used to plot the I/V characteristic curve of the LED. To produce the data, a test
circuit will be constructed using the PB-103 Proto-Board. The test circuit will be
powered by a DC power supply. Test equipment (TE) consisting of DMMs will be
used to measure the following parameters:
Circuit input voltage (Vin)
Voltage drop across the LED (Vd)
Current through the LED (Id).
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Experiment 3 – Measuring the I/V Characteristics of a LED.
1. Construct the circuit shown in Figure 2. Utilize the Keithley DMM to measure the
current flowing through the diode (Id), a Fluke DMM to measure the voltage drop
across the diode (Vd), and a Fluke DMM to measure the voltage input (Vin) to the
circuit.
2. Take data samples between Vd = -2V and Vd = 1.8V. Collect 4 evenly spaced
samples between -2V and 0V and 10 evenly spaced samples between 0V and 1.8 V.
Make sure you do not exceed the wattage rating for the diode. Also, make sure you
note when the LED begins to illuminate.
4. Data Reduction and Lab Report
This Lab submittal will be an informal report. Your report should be in Word with
graphics pasted in.
The items listed below are the minimum that should be included in your report.
A. Experiment 1 Data: Measuring the I/V Characteristics of a Silicon Diode
1. A schematic of your test circuit.
2. A table showing the measured values Vin, Vd, Id, and computed power being
dissipated by the diode (Wd).
3. An Excel scatter graph of your I/V data. Use smooth lines and size 3 markers.
Make sure all graph axes are labeled properly and the graph has a proper title.
4. Answers to the following questions:
a. At approximately what voltage does the diode begin to conduct any
appreciable current (≈1mA)?
b. After the diode begins to conduct appreciable current, what is its
approximate average resistance?
c. What is the purpose of the resistor (Rs) in series with the diode?
d. What is the most current that could flow through the diode in the test circuit
if Vin was set at 30V?
A. Experiment 2 Data: Measuring the I/V Characteristics of a Germanium Diode
1. A schematic of your test circuit.
2. A table showing the measured values Vin, Vd, Id, and computed power being
dissipated by the diode (Wd).
3. An Excel scatter graph of your I/V data. Use smooth lines and size 3 markers.
Make sure all graph axes are labeled properly and the graph has a proper title.
4. Answers to the following questions:
a. At approximately what voltage does the diode begin to conduct any
appreciable current (≈1mA)?
b. After the diode begins to conduct appreciable current, what is its
approximate average resistance?
c. What is the most current that could flow through the diode in the test circuit
if Vin was set at 30V?
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A. Experiment 3 Data: Measuring the I/V Characteristics of a LED
1. A schematic of your test circuit.
2. A table showing the measured values Vin, Vd, Id, computed power being
dissipated by the diode (Wd) and values when the LED illuminates.
3. An Excel scatter graph of your I/V data. Use smooth lines and size 3 markers.
Show the region where the LED produces light. Make sure all graph axes are
labeled properly and the graph has a proper title.
4. Answers to the following questions:
a. At approximately what voltage does the diode begin to conduct any
appreciable current (≈1mA)?
b. After the diode begins to conduct appreciable current, what is its
approximate average resistance?
c. At what value of current does the LED commence illumination?
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