UNIVERSITI TENAGA NASIONAL Dept of Electronics and Communication Engineering College of Engineering Semester: 2 Academic Year: 2011 / 2012
COURSE CODE:
EEEB141
COURSE INSTRUCTOR: TITLE:
EXPERIMENT NO:
1
DATE:
TIME:
Silicone & Zener Diode Characteristics
OBJECTIVE:
MARKS
The objectives of this laboratory experiment are to study the I-V characteristics for normal and zener diodes
PRELAB : 1a 1b 2a 2b
/0.5 /0.5 /0.5 /0.5 / 2
EXPERIMENT RESULT: Part A : Silicon Diode
Table 1-1 Table 1-2 Forward-biased graph Reversed-biased graph
/2 /2 /2 /2
Part B : Zener Diode Table 1-3 Zener diode graph
/2 /2
/ 12 POST LAB: Question 1: a b
/1 /1
Question 2: a b c
/1 /1 /1 / 5
CONCLUSION:
/ 1 TOTAL
INSTRUCTOR COMMENTS:
/ 20 STUDENT NAME:
STUDENT ID:
GROUP MEMBER:
STUDENT ID:
SECTION: WORKBENCH NO:
LAB 1
SILICONE & ZENER DIODES CHARACTERISTICS
LEARNING OBJECTIVES
By the end of this experiment, you should be able to: Measure and plot the forward and reverse-biased characteristics for a diode. • Measure and plot the characteristics for Zener diodes. • MATERIALS
Resistors: Components:
1 × 330Ω, 1 × 1.0MΩ, 560Ω 5W 1 × 1N4148 or equivalent, 1 × 1N4740
EQUIPMENT • •
Tektronix PS280 DC Power Supply Fluke 45 Dual Display Multimeter
PRE-LAB ASSIGNMENT
Answer the following questions: 1.
Silicon Diode Characteristics a. The semiconductor diode is basically a pn junction. Draw a simple diagram to show the cross section of the diode. On the diagram, indicate the p and n regions as well as the anode and the cathode of the diode.
b. Sketch the I-V characteristic of an ideal diode.
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2.
Zener Diode a. Sketch the general I-V Zener diode characteristics indicating all important points.
b. State two differences between normal diodes and Zener diodes.
EEEB 141ELECTRONICS DESIGN LAB, Lab 1
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BACKGROUND
Diode is a device formed from a junction of p-type and n-type semiconductor materials. The lead connected to the p-type material is called ‘anode’ while the lead connected to the ntype material is called ‘cathode’. Normally, the cathode of a diode is marked by a solid line on the diode.
Cathode
Anode
One important application of diode is rectification. When it is forward biased (higher potential connected to the anode), the diode will allow current to pass. When it reversed biased (higher potential connected to the cathode), the current is almost zero or blocked. I
Reverse Bias Breakdown Region
Reverse Bias Region
Forward Bias Region V
The diode can be thought of a switch that closes (on) when the diode is forward biased, and opens (off) when diode is reversed biased. Another important characteristic of a diode is the reverse bias breakdown. Applied reverse bias voltage cannot increase without limit. At some point, breakdown occurs and the reverse-bias direction increases rapidly. Breakdown may damage to a normal diode. However, diodes called Zener diodes can be designed and fabricated to provide a specific breakdown point. IN-LAB ACTIVITIES
PART A (Normal Diode- Characteristic) 1. Measure and record the resistance of the resistors. Then check your diode with the multi-meter. Measure the forward and reverse resistances of the diode. Record and tabulate the data. 2. Construct the forward-biased circuit shown in Figure 1-1. Set the power supply for zero volts.
EEEB 141ELECTRONICS DESIGN LAB, Lab 1
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Figure 1-1 3. Monitor the forward voltage drop, V D,FOR , across the diode, D1. Slowly increase VS to establish 0.35V across the diode. Measure the voltage across the resistor, VR1, and compute ID FOR . Record and tabulate the data in Table 1-1. 4. Repeat step 3 for voltage VD,FOR of 0.40V, 0.45V, 0.50V, 0.55V, 0.60V, 0.65V, 0.70V, and 0.75V. 5. Connect the reverse-biased circuit shown in Figure 1-2. Set the power supply, VS to 5.0V, and then to 10.0V, 15.0V, 20.0V, and 25V. Measure V D REV and compute ID,REV for each voltage applied. Record and tabulate the data in Table 1-2.
Figure 1-2
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RESULTS Resistor Resistances R 330Ω: ……………… Ω
Diode Resistances Forward bias: ……………… MΩ
R 1MΩ: ……………… MΩ
Reverse bias: ……………… MΩ
VD,FOR (V) VS (V) Nominal
VR1 (V)
ID
=
VD,REV (V)
ID
=
Measured
VR1 R 1
(A)
0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 Table 1-1 VS (V) VR1 (V) Nominal
Measured
VR1 R 1
(A)
5 10 15 20 25 Table 1-2
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PART B (Zener Diode characteristic) 1. Build the circuit shown in Figure 1-3 using a 5.0V Zener diode.
Figure 1-3 2. Monitor Vin and Vout and record Vout for Vin values from 0 – 10V at intervals of 0.5V. 3. Record your results in Table 1-3. 4. Plot graphs of current, I against the output voltage, V o for the Zener diode on a graph paper.
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RESULTS
Vin
Vout
VR
(V)
(V)
(V)
I
=
VR R
(mA)
Vin
Vout
VR
(V)
(V)
(V)
0.5
5.5
1.0
6.0
1.5
6.5
2.0
7.0
2.5
7.5
3.0
8.0
3.5
8.5
4.0
9.0
4.5
9.5
5.0
10.0
I
=
VR R
(mA)
Table 1-3
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POST LAB DISCUSSIONS
1.
Silicon Diode Characteristic a. Describe your observation/understanding based on the plotted forward biased diode curve graph.
b. Discuss the difference from the experimental I-V plot, compared to the ideal diode I-V characteristic drawn in the pre-lab question.
2.
Zener Diode Characteristic a. Describe your observation based on the plotted I-V graph in Part B.
b.
If the same experiment was repeated using a 10.0 V Zener Diode, explain the expected resulting I-V characteristic. Sketch the expected I-V graph.
c. Name an example of possible application of a Zener diode? Explain briefly.
CONCLUSIONS
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Free Plain Graph Paper from http://incompetech.com/graphpaper/plain/
Free Plain Graph Paper from http://incompetech.com/graphpaper/plain/
Free Plain Graph Paper from http://incompetech.com/graphpaper/plain/
