SKEE 2742 BASIC ELECTRONICS LAB

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1 Faculty: Subject Subject Code : SKEE 2742 FACULTY OF ELECTRICAL ENGINEERING : 2 ND YEAR ELECTRONIC DESIGN LABORATORY Review Release Date Last Amendment Procedure Number : 1 : 2013 : 2013 : PK-UTM-FKE-(0)-10 SKEE 2742 BASIC ELECTRONICS LAB EXPERIMENT 1 DIODE

2 DIODES PART 1 ZENER DIODE CHARACTERISTIC Objective 1. Become familiar with basic electronic instruments. 2. Understand a Zener Diode IV Characteristic. Materials Required Equipment Theory zener diode 5.1V (1N4733) Resistors (1kΩ) Breadboard (Use own breadboard) Oscilloscope, DC power supply, Ammeter, Voltmeter, Multi-meter Zener Diode All diodes experience avalanche breakdown when the reverse voltage becomes large enough. In the breakdown region, the current may rise rapidly with very little increase in reverse voltage. A zener diode is designed to experience breakdown at a fixed reverse voltage. Commercial zener diodes are available for the range from 3.3V to several hundred volts. When forward biased, a zener diode has the same characteristic as any other forward biased diode. Figure 1.1 shows the I-V characteristic of a typical zener diode. The reverse breakdown region can be approximated to a straight line with a slope of 1/rz where rz is the incremental resistance in this region. rz can be as small as 5Ω. The intercept Vzk is known as the zener knee voltage. Figure 1.1 Application of zener diode employing reverse biased feature can be found in dc power supply system functioned as voltage regulator. 1

3 Pre-lab of Zener Diode Determine the specifications of the zener diode that will be used in the experiment. Use MULTISIM or any equivalent simulation software package and use appropriate circuit to obtain the characteristic graph of the zener diode used in this experiment. (Note: All or any pre-lab works must be completed before coming to the lab and must be handed-in to the lab instructor during entering the lab and at the beginning of lab session) Procedure Zener diode I-V characteristics 1. Connect the circuit in Figure For V s between 0 to 20V, obtain values for I z and V z. (I z and V z have negative values). 3. Complete Table Plot a graph of I z versus V z. 5. From your graph obtain the value of V zk and estimate R z. Figure 1.2 Vs(V) Vz(V) Iz(mA) Table 1.1 2

4 PART 2 ZENER VOLTAGE REGULATOR Objective 1. Become familiar with basic electronic instruments. 2. Practice measurements and calculations for a regulated power supply. Material Required Transformer, 2.25A, 15vrms Zener Diode 12V (1N4742) Capacitor: 100μF 2 diodes (IN4001) 12V IC regulator (7812) Resistors: (2X1kΩ, 100kΩ) Breadboard (Use own breadboard) Equipment Digital Voltmeter (DVM) Oscilloscope Pre-lab of Zener Voltage Regulator Use MULTISIM or any software of equivalence to simulate and to produce all relevant waveforms for zener voltage regulator circuit given in figure 1.3. Procedure 1. Connect the circuit in Figure Observe and sketch the waveform voltage with complete values and labels of V 01 (V across transformer at the secondary), V 02 (V across rectifier) and V L. 3. Measure and record the DC voltage of V L with and without load resistor, R L. Calculate the voltage regulation, V reg. + 1N4742 Figure 1.3 3

5 6. Replace the Zener diode with a LM7812 voltage regulator as in Figure 1.4. No series resistor is necessary with the IC regulator. 7. Measure and record in a table the DC voltage across the load with and without load resistor, R L.. 8. Compare the results of the two experimental circuits and state your observation. Reminding note: Keep this final circuit connected on the breadboard until all experiments completed as it is going to be used again for next two following experiments. Figure 1.4 4