Experiment No. 13: Characteristics of Zener Diode (PDF)
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This experiment investigates the characteristics of a Zener diode in reverse bias and determines its reverse breakdown voltage, examining how the output voltage remains constant (voltage regulation) even with fluctuations in the input voltage. The procedure includes connecting a circuit, varying the input voltage and observing corresponding currents and voltages through the diode. This data aids in creating a graph between voltage and current for the Zener diode, illustrating the Zener diode's voltage regulation capability.
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## EXPERIMENT NO. 13 ### CHARACTERISTICS OF ZENER DIODE **Aim:** To study the characteristics of Zener diode in reverse bias and determine its reverse breakdown voltage. **Apparatus:** DC power supply, Milliameter, Voltmeter, Connecting wires etc. **Theory:** The Zener diode is used to regulate t...
## EXPERIMENT NO. 13 ### CHARACTERISTICS OF ZENER DIODE **Aim:** To study the characteristics of Zener diode in reverse bias and determine its reverse breakdown voltage. **Apparatus:** DC power supply, Milliameter, Voltmeter, Connecting wires etc. **Theory:** The Zener diode is used to regulate the voltage across a load when there are variations in the supply or load current. The Zener regulator consists of a current limiting resistor R connected between the output of the bridge rectifier with the filter & the load. The Zener regulator is connected in parallel with the load R<sub>L</sub>. The Zener diode is reverse biased. It is selected with a breakdown voltage V<sub>z</sub> equal to the desired across the load. R<sub>L</sub> = V - V<sub>z</sub> - V. As long as V<sub>i</sub> is greater then V<sub>z</sub> the Zener diode operates in the breakdown region & output voltage remains constant. **Circuit diagram:** ``` + | | I<sub>z</sub> | Variable D.C. Power Supply + | | V | + | | RS Z | | V<sub>z</sub> | | R<sub>L</sub> | + | | I<sub>L</sub> | | - V = Variable input voltage R = Resistance mA = milliameter Z = Zener Diode R<sub>L</sub> = Load Resistance ``` **Procedure:** 1. Connect the circuit as shown in the circuit diagram. 2. Vary the voltage (V<sub>i</sub>) of the D.C. supply as shown in the observation table. 3. Note the current through the Zenerdiode (I<sub>z</sub>). 4. Measure the voltage across Zenerdiode (V<sub>z</sub>) 5. Plot a graph of I<sub>z</sub> (-ve Y axis) V<sub>z</sub> (-ve X axis) 6. Note the breakdown voltage (V<sub>z</sub>). **Observation table:** | Sr. No. | INPUT VOLTAGE (V<sub>i</sub>) volts | CURRENT THROUGH ZENER (I<sub>z</sub>) mA | OUTPUT VOLTAGE ACROSS ZENER (V<sub>z</sub>) volts | |---|---|---|---| | 1 | 1 | 0 | 1.03 | | 2 | 2 | 0 | 2.96 | | 3 | 3 | 0 | 4.86 | | 4 | 5.1 | 0 | 6.28 | | 5 | 6.5 | 0.42 | 6.60 | | 6 | 7.2 | 1.82 | 6.72 | | 7 | 9.4 | 3.75 | 6.75 | | 8 | 12.2 | 8.17 | 6.78 | | 9 | 14 | 11.04 | 6.80 | | 10 | 17.4 | 16.06 | 6.82 | The graph describes a Zener diode characteristic curve. The curve has a steep slope for low values of input voltage, reaching the reverse breakdown voltage at approximately 6.78 volts. As the input voltage increases beyond the breakdown voltage, the current increases significantly, while the output voltage remains relatively constant at around 6.8 volts. This behavior displays the Zener diode functioning as a voltage regulator, maintaining a consistent output voltage despite fluctuations in the input voltage. *** ## Experiment - Graph Visualization ### Scale: * x-axis = V<sub>z</sub> = 2cm = 1 volt * y-axis = I<sub>z</sub> = 2cm = 1 miliampere The graph is a visual representation of the relationship between output voltage (V<sub>z</sub>) across the Zener diode and the current (I<sub>z</sub>) passing through it, as collected in the observation table. The x-axis displays the output voltage, and the y-axis represents the current. The graph shows a fairly flat portion of the curve above the breakdown voltage, which indicates that the Zener diode maintains a constant voltage across it, irrespective of current changes. This demonstrates the Zener diode's ability to regulate voltage effectively. You can imagine the plotted points from the observation table being connected by a smooth line. The line would initially have a small slope until it plateaus at a higher current, which represents the Zener diode entering the breakdown region.
