Objective
The objective of this lab is to study the voltage characteristics of a diode to draw it's diode curve.
Equipment Used
1) ET Trainer
2) Multimeter
3) EL - 200 Lab kit
Procedure
1) Measure the forward and reverse resistance of the diode
2) Assemble
the following circuit:
3) Measure the voltage across the resistor
4) Measure the current through the circuit
5) Reverse the diode, and change the resistor to 1MW and repeat steps 3 and 4
6) Repeat steps 3 through 5 changing the using the following voltages:
a) 1.0v
b) 2.0v
c) 4.0v
d) 6.0v
e) 8.0v
f) 10v
g) 15v
7) Assemble the following circuit
8) Measure the voltage across the resistor
9) Measure the current through the circuit
10) Reverse the diode and repeat steps 8 and 9
Data
A) Table 1: Forward and Reverse Biased Resistances:
|
|
Forward: |
Reverse: |
|---|---|---|
|
Resistance |
18.5KW |
'W |
B) Table 2: Forward Biased Voltages and Currents:
Circuit voltage:
|
Diode: |
.5v |
1.0v |
2.0v |
4.0v |
6.0v |
8.0v |
10v |
15v |
|---|---|---|---|---|---|---|---|---|
|
Voltage |
.50v |
.55v |
.60v |
.60v |
.60v |
.61v |
.61v |
.61v |
|
Current |
.065mA |
.391mA |
1.370mA |
3.423mA |
6.50mA |
7.92mA |
9.80mA |
15.31mA |
B) Table 2: Reversed Biased Voltages and Currents:
Circuit voltage:
|
Diode: |
1.240v |
2.0v |
4.0v |
6.0v |
8.0v |
10v |
15v |
|---|---|---|---|---|---|---|---|
|
Voltage |
1.179v |
1.814v |
2.401v |
2.606v |
2.727v |
2.819v |
2.974v |
|
Current |
0.0000mA |
0.0000mA |
.0001mA |
.0020mA |
.0035mA |
.0055mA |
.0101mA |
*Note: 1.240v in this circuit is the lowest attainable voltage*
C) Table 3: Forward vs. Reverse Bias for Schematic 2:
|
|
Forward Bias |
Reverse Bias |
|---|---|---|
|
Voltage: |
9.31v |
5.05v |
|
Current: |
44.7mA |
24.24mA |
Results
A) Table 1: Forward Biased Results:
Circuit voltage:
|
Diode: |
.5v |
1.0v |
2.0v |
4.0v |
6.0v |
8.0v |
10v |
15v |
|---|---|---|---|---|---|---|---|---|
|
Voltage |
.50v |
.55v |
.60v |
.60v |
.60v |
.61v |
.61v |
.61v |
|
Current |
.065mA |
.391mA |
1.370mA |
3.423mA |
6.50mA |
7.92mA |
9.80mA |
15.31mA |
|
Resistance |
7.69KW |
1.41KW |
438W |
175W |
92W |
77W |
62W |
40W |
B) Table 2: Reversed Biased Results:
Circuit voltage:
|
Diode: |
1.240v |
2.0v |
4.0v |
6.0v |
8.0v |
10v |
15v |
|---|---|---|---|---|---|---|---|
|
Voltage |
1.179v |
1.814v |
2.401v |
2.606v |
2.727v |
2.819v |
2.974v |
|
Current |
0.0000mA |
0.0000mA |
.0001mA |
.0020mA |
.0035mA |
.0055mA |
.0101mA |
|
Resistance |
'W |
'W |
24.01MW |
1.303MW |
779.1KW |
510.9KW |
294.5KW |
*Note: 1.240v in this circuit is the lowest attainable voltage*
C) Diagram 1: Schematic 1 Enlarged view:
D) Diagram 2: Schematic 2 Enlarged View:
E) Diagram 3: Graph of Diode Curve:
Answers
To Lab Questions
1) Q: Plot the Voltage vs. Current for the diode:
A: 
2) Q: Calculate the bulk resistance for the diode:
A: The bulk resistance is:18.5KW.
3) Q: Why do the values of forward resistance and reverse resistance change as the diode's applied voltage change?
A: During forward biased, the diode has a constant voltage drop so it appears to be a variable resistance. During reversed bias, the diode has enough resistance as to let a nearly constant voltage through until it hits breakdown voltage.
4) Q: What approximations were used in this experiment and why?
A: The primary approximation made was that the resistor values were exact. Also, that the multimeters were accurate and did not influence the circuit's operation.
Conclusions
From the data collected, ample information is given to draw a diode curve. The objective was therefore accomplished.
Attachments