Main Difference Between PN Junction Diode and Zener Diode

The main difference between PN Junction Diode and Zener Diode is, PN Junction diode always conducts current only in one direction but Zener Diode can conduct current in one direction at normal condition and conduct current in both directions when the voltage across it crosses the zener voltage.

There is little constructional difference between PN junction diode and Zener diode. Here we will discuss all important differences between PN Junction Diode and Zener Diode.

PN Junction Diode VS Zener Diode

1. PN Junction diodes are not heavily doped that is why it can not be used in reverse breakdown condition but Zener diodes are heavily doped and it can be used in reverse bias condition.

2. PN junction diode can conduct current in one direction but Zener diode can conduct current in both direction.

3. The breakdown voltage rating of PN Junction diode is more than the Zener diode. Once the PN junction Down breaks down in reverse bias it will damaged while zener diode work properly at reverse bias also.

4. The PN Junction diode will be damaged if a large reverse bias voltage is applied across it but Zener Diode is mainly designed to use in reverse bias condition.

5. PN Junction Diodes are used for rectification purposes and also used as a freewheeling diode in some of the circuits on the other hand Zener Diodes are used for voltage regulation, protection purposes.

6. PN Junction Diodes are to be connected in forward bias for its operation and it cannot be used for voltage regulation purpose but Zener Diode can be connected in reverse bias for voltage regulation.

Difference between the application of PN Junction Diode and Zener Diode

As you see in the above circuit diagram both PN Junction Diode and Zener Diode are used. Here the PN Junction diode is used to convert the Alternating Current(AC) to Direct Current(DC). Obviously, it is a half wave rectifier circuit. During the positive half cycle, the PN Junction diode will conduct and during the negative half cycle, it blocks the flow of current. 

A capacitor is connected in parallel to filter the impure DC supply. The capacitor filter the impure DC.

The Zener Diode is connected in reverse for voltage regulation. When an overvoltage occurs then the voltage across the Zener diode will increase and it goes beyond the Zener break down voltage and the Zener diode will start conducting current through it. 

When current start flowing through the Zener Diode then a voltage will be dropped by the Zener Diode and protect the circuit from overvoltage and it keep constant the voltage across the load.

Thus a PN junction diode and Zener Diode works differently in a circuit.

Read Also:

• How and Why [Zener Diode] Regulate Voltage in Reverse Bias?
• What is Diode? Types, Symbols and Applications of Diode
• [Main Purpose] of using Freewheeling or Flyback Diode
• [Main Difference] Between MOSFET and BJT
• [Actual Difference] between SCR and TRIAC Explained

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