Zener Diode ExperimentPublished on 24/7/2018 & updated on 7/11/2018
We need to connect the circuit as given in the diagram above. The experiment is fairly simple to perform. First, we will plot the curve in reverse biased mode. For that, we increase the reverse bias voltage slowly and in small steps. While doing so, keep noting down the ammeter reading and the voltmeter reading. There are two ammeters here, one connected in series with the Zener diode and another one connected in series with the resistance 3.3k Ω. Let’s call the first one as A1 and the second one as A2. If you keep doing so, after a particular value of reverse bias voltage, the value of current in A1 will spike suddenly. Note down the voltmeter reading at this point. The voltmeter reading is the Zener breakdown voltage. Keep increasing the reverse bias voltage further. We will see that the voltage across the diode remains constant whereas the current through it keeps on increasing. Note down the ammeters and voltmeter readings at different values of reverse bias voltage. Tabulate the values of current and voltage. Do the same experiment by connecting the Zener diode in the forward bias. Note down the current and voltage reading.
Your table should look something like the one shown above. Populate the values in the table. Then draw the graph corresponding to these values. You will get the characteristic curve of Zener diode. Note down the value at which the current increases rapidly when in reverse biased mode. The voltage at this value is the Zener breakdown voltage. Note down this voltage separately.
Different Zener diodes have a different breakdown voltage. We should select a Zener diode with a breakdown voltage approximately equal to the voltage we need across the device. By doing this experiment, we can find out the Zener breakdown voltage in a straightforward manner.
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