The official definition of the diode says that it is an element that has a different conductivity, depending on the direction in which the electric current flows. Its use is necessary in chains that need to limit its path. This article will talk in more detail about the device of the diode, as well as what types exist and how to distinguish them.
Appearance story
Work related to diodes began to be carried out simultaneously by two scientists at once - the British Frederick Guthrie and the German Carl Brown. The discoveries of the first were based on tube diodes, the second on solid-state. However, the development of science of that time did not allow a major breakthrough in this direction, but they gave new food for the mind.
Then, after a few years, Thomas Edison re-opened the 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, until the beginning of the 20th century, diodes were called rectifiers. Then the scientist William Henry Ickles applied the two roots of the words - di and odos. The first is translated from Greek as "two", the second - "way". Thus, the word "diode" means "two ways."
Principle of operation 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 low diode resistance.
If there is a positive potential at the cathode, then the diode is not open, it has high resistance and does not pass electric current.
How is a diode arranged?
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 thread of small diameter.
There may be a special wire inside the cathode. It has the property of heating under the influence of electric current and is called a “heater”.
The substances used in the manufacture, most often silicon or germanium. One side of the element has a lack of electrons, the second - on the contrary, their overabundance. Between them there is a boundary, which provides a pn transition. It is he who allows you to conduct current in the right direction.
Characteristics of Diodes
When choosing an element, they are mainly guided by two indicators - the limiting reverse voltage and the maximum current strength.
The use of diodes in the home
One vivid example of the use of diodes is a car generator. It contains a complex of several such elements, which is called the "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 unit of many electronic devices necessarily contains diodes.
Types of Diodes
Basically, elements can be divided into two groups. The first is the type of semiconductor diodes, the second is not semiconductor.
The first group was widely spread. The name comes from the materials of which the diode is made: two semiconductors or a semiconductor with metal.
There is also a number of special types of diodes that are used in special circuits and devices.
Zener diode or zener diode
This type is characteristic in that when a breakdown occurs, a sharp increase in current occurs with high accuracy. This feature is used in voltage stabilization.
Tunnel
In simple words, this type of diode forms a negative resistance on the current-voltage characteristic. It is mainly used in amplifiers and generators.
Reversed diode
It has the property of significantly lowering voltage in the open mode. It is also based on a tunneling effect similar to the previous diode.
Varicap
Refers to the type of semiconductor diodes, which have an increased capacity, controlled electrically in the event of a change in reverse voltage. Used in tuning and calibration of oscillatory circuits.
Light-emitting diode
A feature of this type of diode is that it emits light when the 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
Has properties that are inverse to the previous instance. That is, it starts 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 cell body. It consists of four parts.
In the first place - a letter or number, meaning the material of which the diode is made. It can take the following values:
- G (1) - germanium;
- K (2) is silicon;
- A (3) - gallium arsenide;
- And (4) - indium.
On the second - the types of diode. They can also have different meanings:
- D - rectifying;
- B - varicap;
- A - microwave;
- And - tunnel;
- C - zener diodes;
- C - rectifying columns and blocks.
In third place is a figure indicating the area of application of the element.
Fourth place - numbers from 01 to 99, meaning the serial number of the 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, for example, dots and stripes. There is no special logic in such figures. 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, however, it performs other functions and has its own design.
The main difference between the diode and the triode is that the latter has three conclusions and the name “transistor” is more often used in its relation. The principle of operation is based on the control of currents in the output circuits using a small signal.
Diodes and triodes (transistors) are used in almost every electronic device. Including processors.
Pros and cons
Before concluding, you can summarize all the information about the diodes and make a list of their advantages and disadvantages.
Pros:
- Low price of diodes.
- Excellent efficiency.
- High resource of work.
- Small sizes, which makes it convenient to place them on the schemes.
- Possibility of using a diode in alternating current.
Of the minuses, perhaps we can distinguish that there is no semiconductor type for high voltages of several kilovolts. Therefore, you will have to use older tube analogues. Also, the effect of high temperatures adversely affects the operation and condition of the element.
Some interesting information about diodes
The first copies were produced using low accuracy. Therefore, the scatter of the resulting characteristics of the diodes was very large, as a result of which the finished devices had, so to speak, to be “scattered”. That is, some diodes, it would seem, of one series could get completely different properties. After dropping out, the elements were marked in accordance with the actual characteristics.
Diodes made in a glass case have one interesting feature - sensitivity to light. That is, if the device, in the composition of which there is such an element, has an opening lid, then the whole circuit can work differently in 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. To determine the type of element by eye, appropriate experience will be required. Well, for beginners, tables and reference books on markings can help.
It is also necessary to have at least a basic understanding of electric current and its properties. Of course, all this took place at school, but who can now randomly remember even Ohm's law?
Therefore, without basic knowledge, diving into the world of electronics will be very problematic.