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Sample Laboratory Report Format
Diode Circuits
Name:
1
ENGNXXXX Spring 201X
Lab # Sample
Summary
Two diode/resistor circuits were built according to the circuit diagrams in both the Prelab and Lab. The
Prelab circuits were simulated in MultiSim and the Lab circuits were created on a breadboard. The voltage into
the circuit (Vin pk) and the voltage out of the circuit (Vout pk) was measured for each of the circuits and viewed
using an oscilloscope. The purpose of this was to demonstrate the characteristics and applications of using
diodes in circuits. The results verify the properties of a rectifier diode.
2
Method
Figures 1 & 2, show the circuits that were used in the Prelab. In the Prelab, the circuits were constructed in
MultiSim and a table of data for Vin pk, Vout pk and the oscilloscope waveforms for Vin and Vout were obtained.
Figures 3 & 4 show the circuits that were built on the breadboard and a table of data and screen shots or pictures
of the oscilloscope waveforms that were taken in order to verify and replicate results between the Prelab and
Lab.
Lab Circuits 3 & 4 were constructed on a breadboard. The AC generator was set for a sine-wave at the
voltage and frequency shown in the corresponding Figures. The oscilloscope was set to the DC coupling mode
with the Channel 1 scope probe connected across the generator leads to measure Vin. Both the + and - peak
voltages were recorded and the waveform captured using a camera. The Channel 1 scope probe was then
connected across the diode to measure Vout.. Both the + and - peak voltages were recorded and the waveform
captured using a camera.
R
Vout
1N4001
8 V(p-p)
1 K HZ AC
Vout
2.2 KΩ
Si
R
2.2 KΩ
8 V(p-p)
1 K HZ AC
Si
1N4001
Figure 2 – PreLab Circuit 2
Figure 1 - Pre Lab Circuit 1
Page 1 of 4
Sample Laboratory Report Format
Diode Circuits
Name:
ENGNXXXX Spring 201X
Lab # Sample
R
Vout
2.2 KΩ
1N4001
8 V(p-p)
1 K HZ AC
Si
R
8 V(p-p)
1 K HZ AC
2.2 KΩ
Figure 3 –Lab Circuit 3
3
Vout
Si
1N4001
Figure 4 – Lab Circuit 4
Results
The values obtained for Vin and Vout for Figures 3 & 4 are listed in Table 2.
Figures 5 shows the Vin and Vout waveforms for Figure 3. Figures 6 shows the Vin and Vout waveforms
for Figure 4.
The results show that when a diode is biased in the proper direction (+ to the anode, - to the cathlode)
and reaches it’s junction potential, current will flow. The voltage across the diode will be its junction
potential, approximately 0.6 V for a silicon diode. When the diode is biased in the opposite direction (- to
the anode, + to the cathode), no current will flow and the diode will essentially act as an open circuit, which
means that voltage across the diode will equal the source voltage.
Table 1. Prelab Circuit Results of Diode circuits
PreLab Circuit
Number
1
2
+VIN, peak
(V)
3.93
3.929
+VOUT, peak
(V)
3.374
3.929
-VIN, peak
(V)
-3.923
-3.946
-VOUT, peak
(V)
-0.000026
-0.557
Table 2. Lab Circuit Results of Diode circuits
Lab Circuit
Number
3
4
+VIN, peak
(V)
3.96
3.96
+VOUT, peak
(V)
3.28
3.23
Page 2 of 4
-VIN, peak
(V)
-3.96
-3.96
-VOUT, peak
(V)
0
-.67
Sample Laboratory Report Format
Diode Circuits
Name:
ENGNXXXX Spring 201X
Lab # Sample
Fig. 5 – Lab Circuit 1
Fig. 6 – Lab Circuit 2
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Sample Laboratory Report Format
Diode Circuits
Name:
4
ENGNXXXX Spring 201X
Lab # Sample
Discussion of the Results
The Lab results demonstrate a strong correlation when compared to the Prelab results. In Figure 3, the
resistor is connected across the output of the circuit, Vout = VR1.
The diode is forward biased for the positive ½ cycle of input voltage, reverse biased for the negative ½
cycle of input voltage. The voltage waveform at the output will mimic the Vin waveform for the positive ½
cycle since current flows through the circuit and voltage is developed across the output (R1). The peak output
voltage will be +Vin pk - 0.6V. This verifies KVL for a series circuit as VD + VR1 = Vin .
On the negative ½ cycle of input voltage the diode is reverse biased (open circuit). All of the applied
voltage is developed across the open circuit VD with no current flow in the circuit, therefore no current flow
through the resistor, therefore no voltage is developed across the resistor. Ohms Law equation, IR = V
(0A)(2.2KΩ) = 0V Therefore VR1 = Vout = 0V.
In Figure 4, the diode is connected so that it is at the output of the circuit, VD = Vout.
For the positive ½ cycle of input voltage, the diode is reverse biased. This means that the diode acts as an
open circuit, VD = Vin, therefore the Vout waveform = the Vin waveform.
The diode is forward biased for the negative ½ cycle of input voltage. The voltage across the diode will
be -0.6V (Vout) for the entire negative ½ as shown in Vin and Vout in Figures 5 & 6.
5
Appendix A –Prelab
All Prelab related data is attached.
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