Difference between a Zener diode and Schottky diode

A diode is a passive device that allows the flow of current in one direction only. But since there are so many types of a diode, how to differentiate between them and most importantly which one to use according to its requirement in our circuit? So by the end of this post, you will have a clear idea about the Difference between a Zener diode and Schottky diode 

Before jumping to Zener or Schottky diode, let’s look at some of the basic characteristics of a diode.

Basic Characteristics of a Diode:-

Diode’s Property Definition
Vf It indicates the forward voltage drop when current flows from the P to N terminal of the diode.
If It is the maximum fwd current a diode can handle
VR It is the reverse break down voltage when current flows from N to P terminal.
IR The amount of current that flows when a diode is reverse biased.
tRR When a diode is switched off suddenly, the fwd current flowing through the diode takes a small amount of time to die down and this time is called Reverse Recovery Time.
Characteristics of a diode
Characteristics of a diode

Schottky Diode

  • Unlike a simple rectifier diode(1N4007), the junction of the Schottky diode is between an n-type semiconductor and a metal plate.
  • Schottky diode, also known as barrier diode is mainly used in low voltage circuits because the forward voltage drop of Schottky diode(Vf) is less than a rectifier diode. The forward voltage drop of a Schottky diode is typically in the range of .25 to 0.5 V whereas the Vf of a rectifier diode is around 0.7 volts.   
  • Let’s say you are working with a low voltage(say 3v) circuit and a diode is being used in that circuit. In this case, it is better to use a Schottky diode because there would be less voltage drop across it. And there will be enough voltage left for further use.
Schottky diode is a Unipolar device
Schottky diode is a Unipolar device
  • Also, electrons are the majority charge carriers on both sides of the junction, thus it is a unipolar device.
  • It is mostly used in high-frequency applications like SMPS. And that’s because of its low-temperature rise and high switching speed pertaining to its small recovery time.
A Schottky diode in an SMPS
A Schottky diode in an SMPS

RECOVERY TIME:

When a diode is switched off suddenly, the fwd current flowing through the diode takes a small amount of time to die down and this time is called Reverse Recovery Time. compare to a normal diode reverse recovery time of Schottky diodes is much smaller, making it suitable to be used in fast switching circuits.

 

Disadvantages of a Schottky diode:

  • Now disadvantage of Schottky is its low breakdown voltage ( 20v to 40v ) making it unsuitable for a rectifier circuit.
A disadvantage of Schottky Diode
A disadvantage of Schottky Diode

Application of a Schottky diode:

  • As an example, let’s say we are designing a buck converter. Since Mosfet in a buck converter switches with a very high frequency, the diode in this circuit should have a high switching speed. Thus Schottky diode is an optimum choice here.

 

Read Difference between Rectifier and Schottky diode OR Difference between Rectifier and Zener diode instead.

 

Zener Diode:

  • A Zener diode is made up of a PN junction but heavily doped compared to a normal diode. As a result, it can undergo breakdown without being damaged.
  • And Due to this property only, Zener is used as a voltage regulator in electronic circuits.
  • In fact, Zener diodes are never used for rectification purposes.
Zener Diode is Heavily doped
Zener Diode is Heavily doped
What is a Voltage Regulator
What is a Voltage Regulator
  • In the circuit given below, a Zener diode is used to prevent the MOSFET gate from being destroyed by clipping off the voltage.
Zener diode as a Voltage Regulator
Zener diode as a Voltage Regulator
  • The breakdown voltage of this Zener is 5.1 volts. Now if accidentally voltage at the gate of MOSFET exceeds 5v, breakdown of the diode occurs and all the current flows through the diode to ground. Thus preventing the MOSFET from getting destroyed.
  • Here’s another circuit in which two Zener diodes are connected facing each other’s p terminal. If an A.C signal is given at the input, one diode clips of voltage in positive half whereas other in negative half and thus we get voltage under the specified limit in both the half cycle of the input A.C voltage.
Zener diodes in a Circuit
Zener diodes in a Circuit

 

Application of a Zener diode:

Digital Voltmeter using Arduino
Digital Voltmeter using Arduino
  • As an example, I used a 5V Zener in the project “Digital voltmeter using Arduino“. It is connected across the capacitor(analog pin) to prevent the Arduino in case the voltage at its analog pin exceeds the 5 volts limit.

And with that being said now you know all the basic differences between Schottky and Zener diode and when to use one.

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