DIfference between diode, Zener diode and 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 diode, Zener diode and Schottky Diode”
So in this post, we are going to see the basic difference between three most widely used diodes: rectifier, Schottky, and Zener diode and when to use one.
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.
Now let’s study diode’s type one by one:
1. Rectifier Diode:
- 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 break down voltage (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 then a rectifier diode typically in the range of .25 to .5 v.
- 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 is the optimum choice.
3. Zener Diode:
- Zener diode is made up of p-n junction but heavily doped compared to a normal diode. As a result, it can undergo break down 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.
- Here’s a circuit in which zener diode is used to prevent the MOSFET gate from destruction by clipping off voltage. Breakdown voltage of this zener is 5.1 v. Now if accidentally voltage at the gate of MOSFET exceeds 5v, diode breakdown and all current flows through the diode to ground. Thus preventing the MOSFET from any kind of destruction.
- Here’s another circuit in which two diodes are connected facing each other’s p terminal. If an A.C signal is given at 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 half cycle of a.c.
- As an example, I used 5V zener in the project “ Digital voltmeter using Arduino” in which it is connected across the capacitor to prevent Arduino in case voltage at its analog pin exceeds 5v.
And with that being said now you know all the basic differences and when to use a rectifier, schottky or zener diode.