Colegio de Muntinlupa
College of Engineering
Computer Engineering Department
Fundamentals of Electronics
Experiment No.1
Diode Fundamentals
Group 4
CpE-2
Razo, Ivan Webster J.
DOP: JANUARY 25, 2022
DOS: JANUARY 30, 2022
Engr. Roselito Tolentino
Instructor
Experiment No. 1
Diode Fundamentals
Objectives
This experiment will enable the student
1. To identify the two types of bias in a diode.
2. To prove principles of the existence of the threshold voltage and characteristic curve
of the diode
Equipment and Materials
Qty
Equipment/Materials
1
DC Power Supply
1
VOM
2
DMM
1
Diode (1N4001)
1
1Kiloohm resistor
1
Breadboard
1 set Connecting wires
Procedures
I.
Biasing
1. Connect the circuit as shown below.
2. Measure the current flowing to the circuit and the voltage across the diode.
3. Repeat the procedure to the circuit below
II.
Threshold Voltage and Characteristic Curve
1. Connect circuit below
2. Set the voltage source to zero. Record the current readings indicated by the ammeter
and the voltmeter across the diode on the circuit.
3. Repeat step 2 for each value of voltage source indicated below.
Data Gathering
In this section, the students gathered data based from the readings given by the voltmeter
and ammeter from the simulation. The provided data shown below were used for data analyzation
for the conducted experiment.
Table 1 – Biasing
Circuit
ID (mA)
VD (V)
Bias
1
0.00999
9.99
Reverse Bias
2
9.287
0.7127
Forward Bias
This table represents the values of the current through the diode and the voltage across
the diode depending on the biasing of the diode which were indicated by the voltmeter and
ammeter.
Table 2 – Threshold Voltage and Characteristic Curve
Supply Voltage
ID (mA)
VD (V)
Remarks
(Conducting / Not Conducting)
0
0
Not Conducting
0V
0.0001
0.0999
Not Conducting
0.1V
0.0002
0.1998
Not Conducting
0.2V
0.000301
0.2997
Not Conducting
0.3V
0.000451
0.3995
Not Conducting
0.4V
0.002735
0.4973
Not Conducting
0.5V
0.03332
0.5667
Conducting
0.6V
0.1037
0.5963
Conducting
0.7V
0.1882
0.6118
Conducting
0.8V
0.2781
0.6219
Conducting
0.9V
0.3706
0.6294
Conducting
1.0V
1.337
0.6626
Conducting
2.0V
2.323
0.6769
Conducting
3.0V
3.314
0.6861
Conducting
4.0V
This table represents the data gathered by conducting the experiment in forward biasing
in which setting the supply voltage as the independent variable while the voltage across the diode
(VD) as the dependent variable.
Graph 1 – Characteristic Curve of the Diode’s Threshold Voltage
Characteristic of the Diode's Threshold Voltage
3,5
Current through Diode (mA)
3
2,5
2
1,5
1
0,5
0
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
Voltage Across Diode (V)
This graph represents the relationship of ID and VD in which states an increasing graph,
creating an exponential function from the two variables.
Analysis of Data
In this section, the gathered data was given interpretation through observation of the graph.
Likewise, correlating all gathered data to the objectives of this experiment specifically on proving
the principles of the existence of the threshold voltage and characteristic curve of the diode.
According from Table 1, the first experiment showed that a diode in reverse biasing, the
measured VD was approximately close to the supply voltage of 10 V with minimal ID almost close
to 0 A. In contrast, the diode in forward biasing, the measured VD was 0.7127 V having 9.287 mA
of ID.
Based from Table 2, the second experiment presented that by increasing the voltage of the
DC supply, the measured VD and ID also increased. Another point was that, if by rounding off the
values of ID to the nearest hundredths from 0 – 0.5 V supply voltage, it was remarked that the
circuit was not conducting.
Figure 1 – Conductive Behavior of the Diode
Aside from that, Graph 1 represented an exponential function from the values of VD and
ID. The values of ID can be described that it started to increase slowly from 0 mA relatively to VD
and increased faster as the value increase over 0.5 V as shown by figure 1 above.
Conclusion
In conclusion, the first experiment presented that there are two types of biasing which were
Forward biasing and Reverse biasing. Reverse biasing was shown by measuring the voltage
across the diode and it was concluded that it has the same voltage as the supply voltage by having
0.99 V with minimal leakages of current close to 0 A. On the other hand, forward biasing was
shown by the value of VD as 0.7127 V. Based from this data, it can be determined that the Diode
acted as a semiconductor with reverse biasing as an insulator while with forward biasing it acted
as a conductor.
Correspondingly, the second experiment was conducted to establish the characteristic
curve of the diode’s threshold voltage. Firstly, increasing the supply voltage also increases VD and
ID however from 0 V to 0.5 V it was concluded that the circuit was not conducting. This is because
the values of ID from that voltage range were approximately as close to zero that if the students
measured its current in a real-life simulation, the value given by the ammeter will negligibly be 0.
Subsequently, as the value was over 0.5 V, the increases faster as it approaches 0.7 V. Therefore,
it can be concluded that the diode was a silicon diode and it does not allow the current to flow
unless VD > 0.5 V and that it will be a fully conducting diode if VD > 0.7 V. Similarly, the second
experiment can be described as a pipe with a cover fixed by a hinge. With increasing water flows,
the cover slowly opens up as it passes through a certain threshold. After a while, significant higher
flow rates can fully open the cover after reaching the limit of the threshold in which this was how
a Diode works when compared to the example.
Lastly, as a student who conducted the experiment, I was able to identify the two types of
bias in a diode and how a diode acts as a semiconductor and how the principles of the existence of
the threshold voltage and characteristic curve of the diode will help me in creating future projects
concerning with diode applications.