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.
- 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.
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.
- 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.
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.
- 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.