Zener Diode as a Voltage Regulator

In Zener diode, there is a conventional current flow from anode to cathode. This silicon semiconductor is designed to function in the condition of reverse bias. However, this forward flow of current can be reversed if the voltage surpasses a specific value which is known as the breakdown or Zener voltage. Further, the application of reverse voltage on the Zener diode ensures that the voltage remains constant for a significant range of current. 

Here, look at the schematic symbol and appearance of a Zener diode. 

Zener Diode as Voltage Regulator

Before you discuss how this diode can be used as a voltage regulator, you must know what a voltage regulator is. It is a system wherein a constant voltage level is maintained either using positive feedback or negative feedback. Here, the output voltage is balanced even if there is fluctuation in voltage supply. 

Furthermore, you must refer to the image below to see how Zener diode can be used as voltage regulator. 

The image depicts a current versus voltage graph. The Zener diode acts as a conventional diode when it is connected in the forward direction. The current flows without much restriction while there can be a voltage drop of about 0.3 to 0.7 Volts. 

However, when the reverse voltages are applied, or reverse feedback is provided, a tiny leakage current is observed between the zener voltage and 0V. After it attains a voltage VZ, there is unrestricted current flow in the system. This voltage at which seamless current flow begins is known as the breakdown voltage. This is how zener diode is used as voltage regulator. 

For example, if you happen to pass a 6V reverse voltage through a diode of 3V, then the measure of voltage across the diode will be 3V only. 

Subsequently, a P-N junction silicon semiconductor is used to make Zener diode regulator instead of any ordinary junction diode. The reason behind this is, an ordinary diode may get damaged if you apply a voltage greater than its breakdown voltage in reverse bias. 

Furthermore, choosing a Zener diode becomes easy as the required output voltage and the input voltage is known from the beginning. Hence, VZ = VL

Now that you have understood the working of Zener diode as voltage regulator answer a few questions based on your understanding. 

Multiple-Choice Questions 

  1. Zener Diode is Designed to Function in Which Region Without Having Any Damage?

  1. Active region 

  2. Forward bias 

  3. Reverse bias 

  4. Breakdown region

Ans: d


  1. Choose the Appropriate Option Regarding the Level of Doping in the Zener Diode. 

  1. Moderately doped 

  2. No doping 

  3. Heavily doped 

  4. Lightly doped 

Ans: c 


Activity For You 

  1. Draw the Zener Diode Voltage Regulator Circuit Diagram. 

Ans:

By studying these concepts, you will be able to explain Zener diode as a voltage regulator in a better way and solve exercise questions. To have a detailed understanding of Zener diode and its working, you should also read up on the related concepts.

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FAQ (Frequently Asked Questions)

1. How Zener Diode Act as a Voltage Regulator?

Ans. When the Zener diode is given reverse bias feedback, there is a small leakage current until it attains the breakdown voltage or a constant voltage. At this point, the current begins flowing seamlessly without any change in voltage. Therefore, the constant voltage helps Zener Diode as Voltage Regulator. 

2. Why is Zener Diode Used as a Voltage Regulator?

Ans. Zener diode is specifically designed for this purpose. The semiconducting silicon material used in the zener diode as voltage regulator experiment helps it function in the forward as well as reverse voltages without breakdown. However, this would not be possible with a standard diode. 

3. What is the Experiment to Study Zener Diodes as a Voltage Regulator? 

Ans. In this experiment, a voltage versus current graph is drawn, which shows the forward and reverse bias given to the diode. The experiment shows that in both conditions, it acts as a voltage regulator as it allows current to flow without showing any fluctuation in output voltage.