Analog Electronics, Diode, Electronics

Difference Between Diode and Zener Diode (Updated)

A major difference between PN junction Diode and Zener Diode is that a PN junction diode can operate in forward bias only whereas a Zener Diode can operate in Forward bias as well as in reverse bias. There are a number of differences between a normal diode and a Zener diode and in this article, we will cover them one by one.

We will cover differences between a Diode and Zener diode with respect to their Symbols, Constructions, Operations, and Applications and after reading this article you will be able to understand all major differences between a Diode and Zener diode.

 

Difference between Diode and Zener Diode

Chart down below shows the difference between Diode and Zener Diode.

PARAMETERDIODEZENER DIODE
Definition Diode is a semiconductor device which allow current in only one direction.Zener diode is special purpose diode which allows current in forward and reverse bias both.
SymbolDiode symbol (2018)Zener diode
OperationDiode is always operated in forward bias it get damages when operated in reverse bias.Zener diode is special diode it can work in forward bias as well as in reverse bias.
DopingDiode is less doped semiconductor device.Zener diode is 1000 times more doped compared to a diode.
ConductivityDiode is uni-directional device (only allow current in one direction).Zener diode is bi-directional device (can allow current in forward and reverse direction).
Breakdown VoltagesDiode has very low breakdown voltage it can not sustain reverse voltages.Zener diode has high breakdown voltages it can sustain large breakdown voltages.
It ObeyDiode obeys Ohm's LawZener diode does not obey Ohm's Law.
ApplicationsDiode is used in rectification, Clipping, Clamping, Voltage Multipliers, Power supplies, Protection Circuits .etc.Zener diode is mostly used in voltage regulators circuits.

 

Diode


A diode is a semiconductor device which is formed when two alternative semiconductors are joined together i.e. when P-layer of Semiconductor and an N-layer of a semiconductor is joined together a junction is formed called a PN junction also called a Diode.

A diode is a current controlling device which is used to control the current in one direction. It is used for the applications like Switching, Rectification, Clipper circuits, Clamper circuits, Voltage multipliers, etc.

The P-layer can be considered as a positive layer because it has holes in the majority whereas N-layer is considered as a Negative layer which has electrons in the majority.

Diode symbol (2018)

A diode is similar to a switch it has two modes of operation. When the diode is forward bias it behaves like a closed switch (ON Switch), and when the diode is reverse bias it behaves like an open switch (Off switch).

When the P-type material is connected with a positive terminal of the battery and N-type material is connected with a negative terminal of the battery then the diode is said to be as Forward bias.

When the N-type material is connected with a positive terminal of a battery and P-type material is connected with a negative terminal of battery then the diode is said to be as Reverse Bias.

During forward bias of the diode, the diode does not conduct immediately, but after a unique forward voltage, it starts to conduct. That forward voltage is commonly known as Diode knee voltage. If the diode is made up of silicon material than the knee voltage is 0.7V and if the diode is made up of germanium then the knee voltage is 0.5v.

Pn junction diode

During reverse bias of diode, the depletion layer starts to widen. Hence a wide depletion region has more resistance for the movement of majority carries thereby electric conductivity is very low. Therefore; no electric current flows in reverse bias of diode.

 

But the minority carriers can flow during reverse bias condition, constituting a very small current in the diode, that small current is temperature dependent. If the reverse bias increase beyond the value of temperature also increases and the minority carriers also increases, which can cause the diode to damage hence reverse bias condition is not used in diode operation.

Therefore, a diode is always operated in the forward bias mode.

Zener Diode


The Zener diode is a special purpose diode which is always operated in the breakdown region. It has the special ability to allow the current to flow in forward direction as well as in the reverse direction, The Zener diode is highly doped as compared to the normal diode.

Zener diode

In terms of the construction, the Zener diode is constructed similar way as a normal diode is constructed; the only difference in terms of their construction is that a diode is less doped as compared to a Zener diode.

The Zener diode has two modes of operation, When the Zener diode is forward bias It behaves same like a normal diode after the knee voltage of 0.7V it conducts the current in one direction just a like a normal diode, but when the Zener diode is reverse biased, it operates in breakdown region which means it does not get damaged in reverse bias but it works in reverse bias region which makes this diode bidirectional semiconductor device.

zener diode construction

During the reverse bias of the Zener diode, the depletion layer starts to reduce, because a Zener diode is a highly doped diode hence it has very thin depletion region, hence the electric conductivity is high. When the reverse voltage reached at breakdown region the current start to increase in reverse direction and Thus, a Zener diode behaves as a voltage regulator.

Key differences Between Diode and Zener Diode


  1. Normal diode is operated in forward bias, whereas a Zener diode is a special purpose diode which is operated in forward bias and reverse bias.
  2. In terms of their electric current conductivity, a Diode is a uni-directional device which conducts current in only one direction whereas Zener diode is a bi-directional device which can conduct in forward bias as well as in reverse bias.
  3. In terms of their doping, A normal PN junction diode is less doped as compared to a Zener diode whereas Zener diode is highly doped semiconductor diode.
  4. In terms of their breakdown voltage, A normal diode has very low breakdown voltage it can sustain less amount of reverse voltage, whereas A Zener diode has a very high breakdown voltage which means it can sustain greater reverse voltage compared to the normal diode.
  5. In terms of their operation, A normal diode can operate only in forward bias whereas a Zener diode can operate in reverse bias as well in forward bias.
  6. A normal diode is a primary device and a Zener diode is a secondary device by just applying more doping to a normal diode a Zener diode can be obtained.
  7. A normal diode obeys Ohm’s law whereas a Zener diode does not obey Ohm’s law. Hence, a diode is PTC device whereas Zener diode is NTC device
  8. In terms of their applications, A normal diode is used as rectification operation, clipping operations, voltage multipliers, etc. whereas a Zener diode is used as a voltage regulator.

Conclusion


The Diode and Zener diode are different from each other with respect to their symbols, construction, operations, and applications, a major difference between diode and Zener diode is the electric current conduction normal diode can conduct in one direction whereas Zener diode is able to conduct in both forward and reverse direction.

Another major difference is that normal diode is less doped whereas Zener diode is a highly doped semiconductor.

A normal diode can get damaged in reverse direction but Zener diode is designed to operate in reverse direction.

A normal diode is used for rectification purpose, clipping, clamping and voltage multiplication operations whereas the Zener diode is commonly used for voltage regulation operations.

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