The official definition of a diode is that it is an element that has a different conductivity, depending on which direction the electric current flows. Its use is necessary in circuits that need to limit its path. This article will tell you more about the device of the diode, as well as what types exist and how to distinguish between them.
History of Appearance
Works related to diodes were started in parallel by two scientists at once - Briton Frederick Guthrie and German Carl Brown. The discoveries of the first were based on tube diodes, the second - on solid state ones. However, the development of science of that time did not allow to make a big breakthrough in this direction, but gave new food for thought.
Then, a few years later, Thomas Edison rediscovered diodes and later patented the invention. However, for some reason, he did not find any application in his works. Therefore, the development of diode technology was continued by other scientists in different years.
By the way, before the beginning of the 20th century, diodes were calledrectifiers. Then the scientist William Henry Eckles applied two word roots - di and odos. The first from Greek is translated as "two", the second - "way". So the word "diode" means "two ways".
Working principle and basic information about diodes
The diode has two electrodes - an anode and a cathode. If the anode has a positive potential with respect to the cathode, then the diode becomes open. That is, the current passes and has a small resistance of the diode.
If there is a positive potential on the cathode, then the diode is not open, has high resistance and does not pass electric current.
How does a diode work?
Basically, the body of the element is made of glass, metal or ceramic compounds. Under the coating are two electrodes. The simplest diode contains a small diameter filament.
There may be a special wire inside the cathode. It has the property of being heated by electric current and is called a "heater".
Substances used in the manufacture, most often silicon or germanium. One side of the element has a shortage of electrons, the other - on the contrary, their excess. There is a boundary between them, which provides a p-n junction. It is he who allows you to conduct current in the right direction.
Diode characteristics
When choosing an element, they are mainly guided by two indicators - the maximum reverse voltage and the maximum current strength.
The use of diodes in everyday life
One of the brightest examplesuse of diodes - car generator. It contains a complex of several such elements, which is called a "diode bridge".
Also, elements are actively used in televisions or radios. In conjunction with capacitors, diodes can extract frequencies from a variety of modulated signals.
Very often a complex of diodes is used in circuits to protect consumers from electric shock.
It is also worth mentioning that any power supply for many electronic devices necessarily contains diodes.
Types of diodes
Basically, the elements can be divided into two groups. The first is a type of semiconductor diodes, the second is non-semiconductor.
It was the first group that became widespread. The name comes from the materials from which the diode is made: two semiconductors or a semiconductor with a metal.
There are also a number of special types of diodes that are used in special circuits and devices.
Zener Diode or Zener Diode
This type is characterized by the fact that when a breakdown occurs, a sharp increase in current occurs with high accuracy. This feature is used in voltage stabilization.
Tunnel
In simple terms, this type of diode forms a negative resistance on the current-voltage characteristic. Mainly used in amplifiers and oscillators.
Inverted diode
It has the ability to significantly lower the voltage in open mode. This is also based on the tunneleffect similar to the previous diode.
Varicap
Refers to a type of semiconductor diodes that have increased capacitance electrically controlled in case of reverse voltage change. Used in tuning and calibration of oscillatory circuits.
LED
The peculiarity of this type of diode is that it emits light when current flows in the forward direction. In the modern world, it is used almost everywhere where lighting with an economical light source is required.
Photodiode
It has the reverse properties of the previous instance. That is, it begins to generate an electric charge when light hits it.
Marking
In order to determine the type, to find out the characteristics of a semiconductor diode, manufacturers put special designations on the body of the element. It consists of four parts.
In the first place - a letter or number, indicating the material from which the diode is made. Can take the following values:
- G (1) - germanium;
- K (2) - silicon;
- A (3) - gallium arsenide;
- And (4) - indium.
On the second - diode types. They can also have different meanings:
- D - rectifiers;
- B - varicap;
- A - microwave;
- I - tunnel;
- С - zener diodes;
- C - rectifier poles and blocks.
In the third place is a number indicating the areaelement application.
Fourth place - numbers from 01 to 99, indicating the serial number of development.
Also, additional designations can be applied to the case. But, as a rule, they are used in specialized devices and circuits.
For ease of perception, diodes can also be marked with a variety of graphic symbols, such as dots and stripes. There is no special logic in such drawings. That is, to determine what kind of diode it is, you will have to look into a special correspondence table.
Triodes
This type of electronic element is somewhat similar to a diode, but it performs other functions and has its own design.
The main difference between a diode and a triode is that the latter has three terminals and the name "transistor" is more commonly used in relation to it. The principle of operation is based on the control of currents in the output circuits with a small signal.
Diodes and triodes (transistors) are used in almost every electronic device. Including processors.
Pros and cons
Before the conclusion, you can summarize all the information about diodes and make a list of their advantages and disadvantages.
Pros:
- Low price of diodes.
- Excellent efficiency.
- High work resource.
- Small size, which makes it convenient to place them on the diagrams.
- Possibility of using a diode in alternating current.
Of the minuses, perhaps, one can single out the fact that there is no semiconductor type for high voltages of several kilovolts. Therefore, you will have to use older lamp counterparts. Also, exposure to high temperatures adversely affects the operation and condition of the element.
Some interesting facts about diodes
The first copies were produced using low precision. Therefore, the spread of the resulting characteristics of the diodes was very large, as a result of which the already finished devices had to be, as they say, “sorted out”. That is, some diodes, it would seem, of the same series could get completely different properties. After screening, the items were labeled according to their actual characteristics.
Diodes made in a glass case have one interesting feature - sensitivity to light. That is, if the device, which includes such an element, has an opening cover, then the whole circuit can work differently in the closed and open state.
Conclusion
In general, in order to fully understand and understand how to properly apply and where to use diodes, you need to study more literature. Appropriate experience is required to determine the type of element by eye. Well, for beginners, tables and marking guides can help with this.
It is also necessary to have at least a basic understanding of the electric current, its properties. Of course, this was all passed at school, but now who can remember offhand even Ohm's law?
Therefore, without basic knowledge, diving into the world of electronics will be very problematic.
