Difference between a normal Rectifier diode and a Schottky diode

A diode is a passive device or component that allows the flow of current in one direction only while blocking the flow of current completely the other way. 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 in this post, I have tried to give you an insight into the “Difference between a normal Rectifier diode and a Schottky diode

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

Basic Characteristics of a Diode:-

Characteristics of a diode
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.

 

What is a Rectifier Diode?

  • A rectifier diode is the simplest p-n junction diode, used mostly for rectification purposes in a half-bridge and full-bridge rectifier. And that’s because of its high break down voltage, typically of the order of 200 to 1000 volts which is obvious.
  • The forward voltage drop (Vf) of a rectifier diode is between 0.7 to 0.9 volt.
Rectifier Diodes in a Full bridge rectifier circuit
Rectifier Diodes in a Full bridge rectifier circuit
  • As an example, let’s say you want to design a bridge rectifier for your ac to dc converter project. For this bridge rectifier, the diode of the 1N4 rectifier series is an optimum choice.
1N4007 diode in a Bridge Rectifier Circuit
1N4007 diode in a Bridge Rectifier Circuit

 

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

 

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.

And ending with the application above, now you know all the basic differences between Schottky and Rectifier diode.

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