Are you a manufacturer dealing with electronic devices and appliances? Diodes are some of the components that make up a functional electric appliance. In this guide, we are going to look at everything that you should know about diodes. At the end of it, you will be able to buy the best diodes.
- 1 What are diodes?
- 2 How do diodes work?
- 3 Concepts about diodes that you should know
- 4 Types of Diodes for Various Applications
- 5 Diode Characteristics
- 6 Buying diodes in China
- 7 ICRFQ: Diodes Distributor in China
What are diodes?
Diodes are passive electrical components whose full name is “rectifier diodes”. They are designed for making it possible to convert alternating current(AC) into direct current(DC). They work by creating a voltage drop when an electric current passes through them.
The word diode comes from the Greek words di (meaning two) and ode (meaning conduction). This is because the diode has two terminals.
The diodes are manufactured in a semiconductor material that conducts electricity when it is given an electric charge.
When no charges are flowing across them, they are said to be non-conducting or off state. They are designed to conduct current only in one direction.
Also, they are designed to work best with direct current (DC). They can’t be used on low or high frequencies.
How do diodes work?
Diodes are made up of two electrodes. The anode is the electrode that receives current while the cathode is the one that gives off current.
Electricity flows through them in only one direction because there’s no flow when they are not supplied with voltage or if there’s a reverse voltage applied to them.
The voltage drop occurs when besides providing power, the current coming from the anode creates a difference in charge between it and the cathode.
This is what makes the difference between how diodes work and transistors or other semiconductor devices that can be used to amplify or switch signals.
The diode also has two main semiconductor materials such as PN diodes (silicon/germanium), Schottky diodes (metals such as gallium nitride), and PIN diodes.
The diode is placed in a circuit so that the voltage across it would be equal to 0 V when no current flows through it. The anode has a positive charge while the cathode has a negative one.
When a positive voltage is introduced across it, the diode starts conducting. On the other hand, if it’s given a negative charge, it becomes non-conducting or off-state. This is why they are also referred to as rectifiers since they can be used to convert AC into DC.
During this process, an electron from the cathode jumps toward the anode. This reduces the energy level of the cathode which causes a reduction in the voltage of the cathode. Meanwhile, there is an increase in the voltage of the anode because it has acquired an electron.
The difference between these voltages is what determines whether current flows or not through them. If this voltage becomes higher than 0 V, then they become conducting. The direction of the current is determined by which terminal has a higher voltage than the other.
If anode has a higher voltage, they are said to be positively diode while if the cathode is higher it’s negatively diodes.
Concepts about diodes that you should know
Here are some key concepts and terms that you should know about diodes. They will give you a better understanding of the diodes working principle.
Forward bias diode
This is a diode that allows current to flow through it in a single direction. In this type, the anode is the positive terminal while the cathode has a negative charge.
Here, when you give it voltage in the forward direction, there’s a difference in potential across the terminals. This difference comes from electrons jumping from cathode to anode.
Backward or reverse bias diode
Contrary to the forward bias diodes, this type of diode is placed in a circuit so that the anode and cathode terminals carry equal amounts of charge. This happens when you give them reverse voltage.
It’s a type of diode, which allows DC to pass through it until the voltage level reaches its zener level. As soon as this voltage is reached, the diode starts conducting. As a result, the current coming from it maintains a steady level till this voltage remains constant.
As compared to zener diodes that always allow a constant amount of current through them no matter what voltage you apply to them, non-zener diodes start conducting only when it reaches a certain voltage level.
This comes from the amount of power that can be supplied or dissipated by the diodes up to several volts. They are not designed for handling large voltages and can get damaged if this happens.
Diodes are used in circuits so that the current flowing through them could be converted to another form. If you want to convert AC into DC, then one way to do this is by using a bridge rectifier.
This is the voltage at which a diode starts conducting.
Maximum repetitive peak reverse voltage
It’s defined as the maximum value of the reverse voltage that can be applied to a diode in several 1-minute cycles and it must not raise this value more than 5% of its initial value.
Types of Diodes for Various Applications
Besides acting as a rectifier, diodes are also used in many other electronics devices. A few of these devices and their work is given below:
This electronic device can be used in amplifying, switching, and even oscillating the signals. Here a small current begins to flow through them when it’s forward biased.
Light-emitting diodes are commonly used for displaying information or giving light in various devices like forwarding cameras, flashlights, etc. They are available in different colors and can be easily seen because of their bright color.
This is a p-n junction diode that converts incoming photons into electrical signals. It works when light falls on its junction and gives out electrons in this process called the photoelectric effect.
This is a diode used to control the frequency of radio waves that pass through it by changing its capacitance. When you apply a reverse voltage to them, varactors change their capacitances and that’s how their frequencies get controlled.
Although diodes can carry currents, unijunction transistors carry very low currents as compared to normal diodes. They support current to flow only in one direction and allow a much higher voltage to be applied on them as compared to the conventional diodes.
When you put a diode in this circuit, it will allow DC to pass through only when the current reaches its peak value.
A photodetector is a device that works on the photoelectric effect produced by light falling onto it. Hence, they are often used as sensors or even for converting light into electricity.
It can be used as a diode as well as a transistor because of the way it works. This is because it allows electrons to flow across its junction without any bias or forward voltage applied to them. It’s mostly used for low current and high-speed switching applications like solar cells, RF oscillators, etc.
It’s similar to zero-bias Schottky diodes but here light is also produced due to the recombination of electrons and holes at the junction of the diode which causes it to emit photons.
They can be used as photodetectors and even for switching applications due to their quick response. The most complicated part of it is that they need a forward bias and so cannot be used as rectifiers or for creating voltage drops across themselves.
Schottky barrier diode
These are basically the combination of p-n junction diode and a metal-semiconductor diode. Their reverse breakdown voltage is very high so they tend to get destroyed when the voltage exceeds their maximum breakdown voltage. This is why they are used in circuits that involve high voltages like power supply, electric vehicles, etc.
Transient suppression diodes
These are mainly used to suppress voltage spikes that are generated when diodes are turned off.
They allow current flow through them in both directions so they are also called bi-directional or dual diodes. It’s mostly used in power converters, inverters among others.
From these diode types, you will definitely find one that matches your application area.
Diode characteristics are the main factors that you should consider while deciding on a diode for your application. You need to know these before making any decision so don’t forget to check them out!
This is the maximum voltage that can be applied across a diode before it breaks down or gets destroyed. The voltage rating is decided upon the maximum voltage that you can apply without causing any damage to the diode.
If you check out the curves of forwarding current versus the forward voltage, there will be a point where these two intersect and it’s called the breakdown voltage. This is usually considered the highest possible voltage that your diode can withstand. The curve is connected to the normal forward voltage drop graph at that intersection point.
This is the time taken by a diode after getting reverse biased until it starts conducting again. It’s usually given in terms of microseconds and depends mainly on its type, size, and construction material.
Reverse Recovery Time
This is also the time taken by the diode to recover but this time after getting forward biased.
Reverse Leakage Current
It’s the minimum amount of current flowing through a diode when it is reverse biased at its rated voltage. The resistance of that section of the diode in that condition is called Reverse Leakage Resistance and it’s denoted by R.
Forward Voltage Drop
The voltage which is dropped across a forward-biased diode is called Forward Voltage Drop or Forward Voltage. It falls in the range of 0.6V to 1.2V for silicon diodes while germanium diodes have a voltage drop of 0.3V to 0.7V.
This is the maximum amount of current which flows through a diode when it is reverse biased at its rated voltage. The resistance of that section of the diode in that condition is called Reverse Current or Peak Reverse Current and it’s denoted by I.
It’s the amount of current flowing through a diode when it is forward biased at its rated voltage. The resistance of that section of the diode in that condition is called Forward Current or Peak Forward Current and it’s denoted by I.
This is the maximum amount of current which can flow through a diode for a very short period of time without damaging it. As a result, it’s denoted by Ip instead of I.
Maximum Average Forward Current
This is the amount of current that can flow through a diode continuously for many hours or days at its maximum case temperature before the forward voltage drop begins to increase gradually. In other words, it’s the maximum average current that can forward bias a diode.
Maximum Forward Current
It’s the limit where overheating of a semiconductor junction begins and it cannot be used in its continuous form for an indefinite amount of time.
Maximum Reverse Current
This is the maximum amount of current which can flow through a diode in the reverse direction at its rated voltage.
Buying diodes in China
If you want to buy diodes in China, the first thing that you should consider is the documentation. If there’s no proper documentation or anything related to regulation, it’s better to walk away from the deal.
After looking at the documents, check if they meet the minimum requirements for the products that you are developing. Let the diode manufacturer in China clarify all the technical details about the diodes that you want to buy.
Also, the first thing that you should consider is the type of diode that you want. We have already outlined different types of diodes and each type is designed for different applications. So, be sure of the type of diodes that you want to buy before taking any further steps.
It is also prudent to inquire about the diode price in China. Contact the manufacturer directly and let them inform you of the cost of diodes of sale. Keep in mind that numerous factors are considered in determining the diode price.
Finally, choose reputable diodes manufacturers and suppliers in China. This is the surest way of getting quality and reliable diodes for electronics.
ICRFQ: Diodes Distributor in China
In case you want to buy diodes in China, consider allowing us to help you with the process. We are a trusted sourcing agent, supplier, and distributor of diodes in China. Our massive experience in this field separates us from the rest.
We source our diodes from reputable manufacturers in China. This assures our customers of the quality of our electronic components. Contact us for the quality diodes for sale.
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