Difference between a normal Rectifier diode and a Schottky diode

A diode is a passive device which 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. “Difference between a normal Rectifier diode and a Schottky diode

So in this post, we are going to see the basic difference between two of the most widely used diodes: Normal rectifier diode and a Schottky diode. 

Before jumping to its type, let’s see some basic specifications of a diode:
1. (Vf): indicates fwd voltage drop when current flows from p to n terminal
2. (If): is the maximum fwd current a diode can handle
3. (Vr): is the reverse break down voltage when current flows from n to p terminal
4. (Ir): The amount of current that flows when a diode is reverse biased

5. (Reverse 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.

 

1. 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 .7 to .9 volt.
Rectifier Diode
Rectifier Diode

 

  • As an example, let’s say you want to design a bridge rectifier for your ac to dc converter project. For this bridge rectifier, diode of 1N4 rectifier series is an optimum choice.
Bridge Rectifier Circuit
Bridge Rectifier Circuit

 

 

2. Schottky Diode

  • Unlike a rectifier diode, junction of Schottky diode is between n-type semiconductor to a metal plate.
  • Schottky diode, also known as barrier diode is mainly used in low voltage circuits because fwd voltage drop of Schottky diode(Vf) is less than a rectifier diode; typically in the range of .25 to .5 v.     
  • Let’s say you are working on a very low voltage(say 3v)  circuit and you need a diode in that circuit. In this case, it is better to use a Schottky diode because there will be very less voltage drop across it. And there will be enough voltage left for further use.

 

Schottky diode
Schottky diode

 

 

  • Also e- 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 in an SMPS. And that’s because of less 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 diode is much smaller, making it suitable to be used in fast switching circuits.

  • 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

 

  • As an example, let’s say we are designing a buck converter like we did in one of the project videos: “Buck converter using Arduino“. Since Mosfet in this circuit is switching with a very high frequency, diode you need in this circuit should have high switching speed. Thus Schottky diode is an optimum choice.

 

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