CHARACTERISTICS OF SEMICONDUCTOR DIODE

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Bruce Sullivan
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1 Exp. No #1 CHARACTERISTICS OF SEMICONDUCTOR DIODE Date: OBJECTIVE The purpose of the experiment is to examine characteristics of a silicon diode and to determine the barrier potential of the diode. From the characteristic curve determine the dc resistance, ac resistance, for forward biased conditions and reverse resistance for reverse biased conditions. EQUIPMENT AND COMPONENTS USED 1N4007 silicon rectifier diode 1 kω resistor, ¼ W 0-15 V dc regulated power supply (0-100)mA, (0 100)µA dc ammeter (0 1)V, (0-30)V dc voltmeter Breadboard THEORY The diode is a device made up of a junction of n-type and p-type semiconductor material. An ideal diode has two regions: a conduction region of zero resistance and a non-conduction region of infinite resistance. In forward bias operation, the silicon diode will not conduct significant current until the voltage reaches about 0.7V, called cut-in voltage. After the point of cut-in voltage small change in voltage causes large increase in current. In reverse bias operation, the diode will not conduct significant current until certain threshold voltage called breakdown voltage. DC resistance or static resistance is the ratio of voltage to current in the forward bias characteristics. AC or dynamic resistance is the reciprocal of the slope of the characteristic curve. The resistance offered by the diode under reverse bias is the reverse resistance. FURTHER READING 1. Robert Boylstad, Louis Nashelsky, Electronic Devices and Circuit Theory, PHI, Theodore F.Bogart, Jeffrey S.Beasley, Electron Devices and Circuits, PHI 3. Robert Diffenderfer, Electronic Devices, Delmar Cengage Learning,

2 CIRCUIT DIAGRAM Figure1: Forward Biased Diode Figure2: Reverse Biased Diode PRACTICE PROCEDURE 1. Forward Bias 1. Construct the circuit as per the diagram shown in figure1. 2. Vary the power supply voltage in steps of 0.1V upto cut-in voltage and thereafter in steps of 1V upto a maximum of 10V. 3. Note down the voltage drop across the diode and the corresponding current. 4. Plot the graph: I F against V F 5. From the plot, find the static resistance, R = V F / I F. 6. Find also the dynamic resistance, r = Δ V F /Δ I F. 2. Reverse Bias 1. Connect the circuit as per the diagram shown in figure2. 2. Vary the power supply voltage in steps of 1V upto 15V. 3. Note down the voltage drop across the diode and the corresponding current. 4. Plot the graph: I R against V R. 12

3 PRELAB Read the specifications of the following diodes from its datasheet and compare the types of diodes offered by different manufacturers: Device Part Number: 1N4001 Device Manufacturer: Peak Repetitive Reverse Voltage, V RRM = Average Rectified Forward Current, I F(av) = Maximum RMS Voltage, V RMS = DC Reverse Voltage, V R = Maximum reverse current I RM = Maximum instantaneous forward voltage drop V F = Device Manufacturer: Peak Repetitive Reverse Voltage, V RRM = Average Rectified Forward Current, I F(av) = Maximum RMS Voltage, V RMS = DC Reverse Voltage, V R = Maximum reverse current I RM = Maximum instantaneous forward voltage drop V F = Device Part Number: 1N4007 Device Manufacturer: Peak Repetitive Reverse Voltage, V RRM = Average Rectified Forward Current, I F(av) = Maximum RMS Voltage, V RMS = DC Reverse Voltage, V R = Maximum reverse current I RM = Maximum instantaneous forward voltage drop V F = Device Part Number: 1N914 Device Manufacturer: Peak Repetitive Reverse Voltage, V RRM = Average Rectified Forward Current, I F(av) = Maximum RMS Voltage, V RMS = DC Reverse Voltage, V R = Maximum reverse current I RM = Maximum instantaneous forward voltage drop V F = 13

4 Exp. No.: OBJECTIVE CHARACTERISTICS OF SEMICONDUCTOR DIODE Date: OBSERVATION Forward Bias Circuit Diagram Table 1: Forward Bias Bias voltage, Vin Volts Diode Forward voltage, V F Volts Diode forward current, I F ma 14

5 Inference Reverse Bias Circuit Diagram 15

6 Table 2: Reverse Bias Bias voltage, Vin Volts Diode Reverse voltage, V R volts Diode Reverse current, I R µa Inference 16

7 UNDERSTANDING & LEARNING 17

8 RESULTS AND CONCLUSION Prepared by: Name: Reg. No.: Experiment Date: ASSESSMENT Report Submission Date: Submission Delay:... Student Task Max. Marks Graded Marks Pre-lab Preparation 20 Inference 10 Signature Results & Conclusion 10 Post-lab / Viva-voce 10 Total 50 18

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