Zener Diode: Understanding the Voltage Regulator

lecture 7-8 (basic electronics )

Zener Diode: Understanding the Voltage Regulator

Introduction:

A Zener diode is a specialized semiconductor device that operates in the breakdown region, providing a stable and well-defined voltage reference. Its unique characteristic makes it invaluable in voltage regulation applications. Let’s delve into the details of the Zener diode:

Basic Structure:

1. P-N Junction:
   • Similar to a standard diode, a Zener diode is created by joining a P-type semiconductor with an N-type semiconductor, forming a P-N junction.
2. Zener Breakdown:
   • Unlike regular diodes, Zener diodes are designed to operate in the reverse breakdown region.
   • The breakdown is known as the Zener breakdown or the avalanche breakdown

Working Principle:

1. Reverse Bias:
   • Zener diodes are typically connected in reverse bias (anode to the negative terminal and cathode to the positive terminal).
   • When the reverse voltage exceeds the Zener breakdown voltage (Vz), a significant current flows through the diode.
2. Voltage Regulation:
   • The Zener breakdown results in a stable and well-defined voltage drop across the diode, maintaining a constant voltage (Vz) across its terminals.
   • This makes Zener diodes suitable for voltage regulation applications.

Characteristics:

1. Zener Voltage (Vz):
   • The Zener voltage is the specific voltage at which the diode enters the breakdown region and begins conducting in the reverse bias.
2. Sharp Breakdown:
   • Zener breakdown occurs sharply and abruptly, making Zener diodes suitable for precise voltage regulation.

Applications:

1. Voltage Regulation:
   • Zener diodes are extensively used in voltage regulators to maintain a constant output voltage.
2. Voltage Reference:
   • They serve as stable voltage references in electronic circuits.
3. Overvoltage Protection:
   • Zener diodes are employed to protect sensitive components from overvoltage conditions.

Zener Diode Characteristics:

1. Dynamic Resistance (rZ):
   • The Zener diode exhibits dynamic resistance, which is the small-signal resistance when operating in the breakdown region.
2. Power Dissipation:
   • The maximum power that a Zener diode can dissipate without being damaged is a crucial parameter.

Conclusion:

Zener diodes play a crucial role in voltage regulation and provide stable voltage references in electronic circuits. Their unique ability to operate in the breakdown region makes them indispensable for maintaining a constant voltage under varying conditions, contributing significantly to the stability and reliability of electronic systems.

Diode vs. Zener Diode: Understanding the Differences

1. Basic Structure:

• Diode:
  • A standard diode is a semiconductor device with a P-N junction.
  • It conducts current in one direction, allowing it to function as a rectifier.
• Zener Diode:
  • A Zener diode is a specialized diode designed to operate in the breakdown region.
  • It has a P-N junction like a regular diode but is specifically engineered for controlled breakdown.

2. Operating Principle:

• Diode:
  • A diode conducts current when forward-biased (anode connected to a higher voltage than the cathode).
  • It blocks current in the reverse-biased direction.
• Zener Diode:
  • A Zener diode operates in the reverse breakdown region.
  • It conducts in the reverse-biased direction once the applied voltage exceeds a specific value (Zener voltage).

3. Breakdown Characteristics:

• Diode:
  • In a regular diode, reverse breakdown is an undesired condition, and it can lead to diode failure.
• Zener Diode:
  • Zener breakdown is a deliberately engineered feature in Zener diodes.
  • It is a controlled and predictable breakdown, allowing the diode to operate in the breakdown region without damage.

4. Voltage Regulation:

• Diode:
  • Regular diodes are not designed for precise voltage regulation.
• Zener Diode:
  • Zener diodes are specifically used for voltage regulation applications.
  • They provide a stable and well-defined voltage reference, maintaining a constant voltage across their terminals in the breakdown region.

5. Applications:

• Diode:
  • Regular diodes are commonly used in rectifiers, amplifiers, and signal demodulation.
• Zener Diode:
  • Zener diodes are primarily used in voltage regulation circuits, voltage references, and overvoltage protection.

6. Characteristics:

• Diode:
  • Diodes have characteristics suited for rectification and switching applications.
• Zener Diode:
  • Zener diodes have a unique characteristic of sharply entering the breakdown region, making them suitable for precise voltage references.

7. Symbol:

• Diode Symbol:
• Zener Diode Symbol:

Conclusion:

While both regular diodes and Zener diodes share a common P-N junction structure, the key distinction lies in their operating principles and intended applications. Regular diodes are designed for rectification and switching, while Zener diodes are tailored for controlled breakdown and precise voltage regulation.

MORE EXPLANATION :

A normal PN junction diode allows electric current only forward bias condition when forward biased voltage is applied to the PN junction diode get allows large amount of electric current and blocks only a small amount of electric current hence a forward biased p and junction diode offer only a small resistance to the electric current.
When reverse biased voltage is applied to the p and junction diode it blocks large amount of electric current and allows only a small amount of electric current and rivers biased p and junction diode offer large resistance to the electric current if rivers by voltage applied to the PN junction diode is highly increased to sudden rise in current occurs . At this point a small increas involtage increases the electric current. This sudden rise in electric current causes a junction breakdown called inner or avalanche breakdown. The voltage at the cleaner up break down occurs is called linear voltage and certain increase in current is called zener current.

A normal PN junction diode does not operate in breakdown region because the excess current permanently damages the diode normal PN junction diodees are not designed to operate in reverse breakdown region there for a normal PN junction diode does not operating reverse breakdown region
What is Zener diode?
Zener diode is a special type of device designed to operate in the zener breakdown result zener diode x like a normal PN junction diode under forward biased condition when forward by voltage is applied to the dinner diode it allowed large amount of electric current and blocks only a small amount of electric current zener diode is heavily dot then the normal p and junction diode and it is a very thin depletion region therefor zener diode allow more electric current and the normal p and junction diode.
Zener diode allows electric current in forward direction like a normal diode but also allows electric current in the river direction if the applied reverse voltage is greater than zener voltage Zener diode is always connected in reverse direction because is specially designed to work in reverse direction.

Definition of zener diode is a p and j junction semiconductor device design to operate Indus river breakdown region The breakdown voltage of diode is carefully set by controlling the dropping level during manufacture .
The name zener diode was named after the American physicist Clarance Melvin Zener who discovered the zinar effect s of the basic building blocks of electronics circuits they are widely used in all kinds of electronic it weapons in a diodes are mainly used to protect electronic circuits from our world breakdown in from our voltage.
Breakdown in Zener diode
There are two types of breakdown regions
Avalanche breakdown And Zener breakdown
* Avalanche breakdown
Occurs in both normal diodes and zener diodes at higher reverse voltage and high reverse voltage is a pride to p and junction diode the free electrons minority careers gains large amount of energy and accelerated to greater velocity is the free electron moving at high speed will collides with the atoms and knock of more electrons these electrons are again accelerated and collide with other atoms. Because of this continuous collosion with atoms allowed number of free electrons are generated. As a result electric current in the diode increases rapidly this sudden increase in electric current mein permanently destroys the normal diode our Avalanche diode may not be destroyed because they are carefully designed to operate in breakdown region avalanche breakdown occurs in zener diode with voltage Vz at greater than 6 V
Zener breakdown
Occurs in heavily dopped PN junction diode because of their narrow depletion region. When reverse bite voltage applied to the diode is increased the narrow depletion region generates strong electric field when reverse biased voltage applied to the diode rich is closer to zener voltage electric current in the depletion region strong enough to pull electrons from their valance band .the valence electrons which can sufficient energy from the strong electric field of depletion region will break bonding with the parent atom the valance electron which break bonding with parent atom will become free electrons these free electrons carry electric current from one place to another place at zener breakdown design a small increase in voltage increase in the voltage.
Zener breakdown occurs at low voltage whereas avalanche breakdown occurs in high reverse voltage.
Zener breakdown occurs in zener diodes because they are very thin depletion region.
Breakdown region is the normal operating region for a zener diode .
Zener diode breakdown occurs in zener diodes with zener voltage Vz less than 6V
Symbol of zener diode :
The symbol of zener diode is shown in below figure . Zener diode consist of two terminals .cathode and anode
In Zener diode , electric current flows both anode to cathode and cathode to anode .
The symbol of zener diode is similar to the normal p-n junction diode ,but with bend edges on the vertical bar .
V-I characteristic of zener diode
The V-I characteristic of zener diode is shown in below figure .when forward biased voltage is applied to zener diode ,it works like normal diode .
However when reverse biase voltage is applied to Zener diode ,it works in different manner.
Advantages
1.Power dissipation.

2.capacity is very high accuracy small size .

3. low cost.
Applications
1.It is normally used as voltage reference.
2.Used in voltage stabilizers or should regulator.
3.Are you stills switching operation.
4.Are used in clipping and clamping circuits.
5.Are used in various protection circuits.