Black diode with a spiral white stripe. Diode designation

Diodes are considered "valves" in an electrical circuit. This is a two-terminal semiconductor element with two active electrodes, an anode and a cathode, between which current can only flow unidirectionally. They are used in various electrical circuits where a one-way diode effect is required. Silicon and germanium are most often used for the manufacture of devices.

Types of diodes

Diodes based on the same principle of operation are not the same in their mode of operation. There are several types of devices, which differ in designations on the diagram, as well as in appearance:

1. Light emitting diodes (LED). When this element allows current to pass between the electrodes, light is generated. The color spectrum depends on the energy gap of the semiconductor;
2. Avalanche diode. Operates in reverse bias and uses the avalanche effect. Since the avalanche process achieves a high degree of sensitivity, it is used for photodetection in other schemes;
3. Laser diode. It differs from an LED in that it generates coherent light. Used in laser pointers, CD and DVD players;
4. Schottky diodes. Have a low forward voltage drop compared to silicon diodes (0.15-0.4 V compared to 0.6 V for silicon diodes). They are built on metal-semiconductor contact;
5. Zener diode. Provides a stable reference voltage;
6. Photodiode. Used to detect light. It is also used in photometry and in generating electricity in solar cells;
7. Varicap. Acts as a capacitor whose capacitance changes depending on the applied reverse voltage;
8. Rectifier diodes;
9. Gunn diodes. Made from GaAs or InP materials and have a negative differential resistance range;
10. Thyristors, or controlled diodes. They have three output contacts.

There are other types of diode elements: point, signal, tunnel, gold-doped, etc.

Structurally, diodes are made in metal, glass, plastic or ceramic cases. Each diode has its own technical parameters for current, voltage, temperatures, etc. Special designations are used to identify the elements.

Marking refers to colored symbols applied to the body of the diode element, providing direct or encoded information about its characteristics.

Marking of domestic diodes

Russian and Soviet devices have a coded color inscription consisting of stripes and dots, the decoding of which can be found in reference books. From it you can understand the material of manufacture, the purpose of the element and its performance characteristics.

In turn, each combination of color symbols corresponds to a code of letters and numbers (GOST 20859.1-89). The color coding of the diodes along with the letter code is included in the table. Partially the code of letters and numbers can be understood immediately, the remaining parameters are grouped in other tables.

For example, the table indicates that the purple stripe on the cathode side indicates KD243A:

• the letter “K” means that the element is made from silicon; instead of the letter for silicon there may be the number 1;
• D – indicates a rectifier diode, maybe a zener diode (C), varicap (V), tunnel diode (I), etc.;
• 2 – operational characteristics (in this case it is intended for a current of 0.3-10 A);
• 43 – number under which the device was developed;
• A – class of a group of elements produced using a common technology.

Diodes from foreign manufacturers

Marking of a diode produced outside of Russia is also done using a certain color marking, indicating alphabetic and digital codes, which can be read from a table. Two main standards apply:

• JEDEC (American);
• PRO-ELECTRON (European).

In the European standard, like the Russian one, the first symbol indicates the material used, then the type and purpose of the element and then the series number are reported. By this number you can understand whether the diode is used in commonly used devices (from 100 to 999) or is produced for installation in a special circuit, then an alphabetic symbol and a two-digit number are used (for example, A96).

Everything is tabulated, and identifying any diode is not difficult.

Important! The location of the cathode terminal should always be looked for where wide stripes are applied.

The American JEDEC standard is less informative than the European standard, but the main characteristics of the device are easy to read.

SMD diodes

SMDs are surface mount devices, microscopic electronic components soldered to the copper side of the board and without long connecting leads. Often it is impossible to apply markings on it, since there is no space for this. If the size is slightly larger, numbers or letters are applied to the element. Some reference data can be found in various tables, but they are incomplete and it is not always possible to find the required element.

SMD diode polarity

Radio amateurs sometimes have difficulty correctly determining the poles of an SMD element.

Polarity designation options:

1. Often there is a triangle, the vertex of which points to the cathode. Simplified, the same symbol is represented by a horizontal line with a protrusion facing the cathode;
2. If only one bar is designated, it is on the negative pole;
3. PLLC devices (white plastic coated) have a slot on the cathode side.

Of the SMD diodes shown in the figure, the one on the far right does not fit any description. In this case, only viewing in the data sheet helps.

LED markings

LED is used in semiconductor optoelectronic devices that emit radiation in the range of visible, infrared and ultraviolet rays.

Most common varietiesSMD LED:

1. RGB-LED. A multicolor diode with structures that allow it to generate three primary colors (R - red, G - green, B - blue). By mixing these colors, you can get any spectrum;
2. Warm White LED – warm white. Color temperature is below 3300 K;
3. Neutral white with a color temperature in the range of 3300-5300 K;
4. Cool white diode with a color temperature above 5300 K.

Numerical symbols indicate the size of the diode element:

1. 3528. Dimensions 3.5 x 2.8 mm. This is a first generation LED;
2. 5050. Dimensions 5.0 x 5.0 mm. Gained high popularity due to good parameters;
3. 5630/5730. Size – 5.6 x 3.0 mm. Successor to the 5050 LED. Generates a large luminous flux. Used for devices with increased power and brightness;
4. 3014. Dimensions 3.0 x 1.4 mm. It appeared on the market not long ago. Small size and high brightness guarantee growth in its use;
5. 2835. Size – 2.8 x 3.5 mm. Also recently sold. Brighter than LED 3014. Increasingly used in lamps with E27, E14 socket;
6. OWL diode (chip on board). A large element consisting of small ones. Reaches power up to 200 W with a luminous flux of up to 10,000 lm. It has a long service life and is used in floodlights.

The designation 30 SMD, 60 SMD indicates how many LEDs are located on a 1 m segment of LED strip. There are 150, 300 or 600 SMD in 5 meter rolls, also with bulbs. The inscription 16 SMD 5730 indicates that the lamp contains 16 LEDs 5.7 x 3.0 mm.

LEDs manufactured using DIP technology have a glass or plastic body and long leads, and are marked in the Russian Federation using a developed color code system.

Color rendering index CRI

This is an important parameter that determines color accuracy. The example here is the sun, which has a CRI of 100. Artificial light sources range from 0-100. The higher the CRI, the more natural the lighting looks.

Important! It is worth looking for LED lamps with CRI > 80.

Different LED manufacturers use their own coding system, which is not standardized. Therefore, you need to look for decoding in special reference books.

Video

Diode marking is a short graphic symbol for the element. The elemental base is currently so diverse that the abbreviations differ quite noticeably. It is difficult to identify the diode: zener diode, tunnel diode, Gunn diode. Varieties have been released that resemble a gas-discharge light bulb. The LEDs light up, adding to the confusion.

Semiconductor diodes

Perhaps the section is called somewhat trivially, when you simply need to distinguish typical diodes from obsolete electronic tubes and modern SMD modifications. Ordinary semiconductor diodes are an easily solvable problem for a radio amateur. The side of the cylindrical body with a disk base and legs contains an easily visible inscription painted with paint.

Semiconductor resistors. Can you tell the difference with the naked eye?

The color of the case does not matter; the size indirectly indicates the power dissipation. Powerful diodes often have a thread for the radiator mounting nut. The result of calculating the thermal regime shows the lack of the body’s own capabilities; the cooling system is supplemented by an external element. Today, power consumption is falling, reducing the linear dimensions of device housings. This allowed the use of glass. The new housing material is cheaper, more durable, and safer.

• The first place is occupied by a letter or number that briefly characterizes the material of the element:

1. G (1) – germanium compounds.
2. K (2) – silicon compounds.
3. A (3) – gallium arsenide.
4. And (4) – indium compounds.

• The second letter in our case is D. Rectifier or pulse diode.
• The third place was chosen by the figure characterizing the applicability of the diode:

1. Low frequency, current below 0.3 A.
2. Low frequency, current 0.3 - 10 A.
3. Not used.
4. Pulse, recovery time over 500 ns.
5. Pulse, recovery time 150 – 500 ns.
6. The same, recovery time 30 – 150 ns.
7. The same, recovery time 5 – 30 ns.
8. The same, recovery time 1 – 5 ns.
9. Pulsed, minority carrier lifetime below 1 ns.

• The development number is composed of two digits and may be absent altogether. Denominations below 10 are padded on the left with a zero. For example, 07.
• The group number is indicated by a letter and determines the differences in properties and parameters. The letter often becomes a key letter, indicating the operating voltage, direct current, etc.

In addition to the markings, the reference books provide graphs by which the problems of choosing the operating point of a radio element are solved. Information about production technology, body material, and weight is indicated. The information helps the equipment designer, but has no practical meaning for amateurs.

Imported designation systems differ from domestic ones and are well standardized. Therefore, using special tables it is not difficult to find suitable analogues.

Color coding

Every radio amateur knows the difficulty of identifying diodes surrounded by a glass housing. One person. Sometimes the manufacturer bothers to apply clear marks and multi-colored rings. According to the notation system, three characteristics are introduced:

1. Markers of cathode and anode areas.
2. Body color, replaced by a colored dot.

According to the state of affairs, at first glance we can distinguish the types of diodes:

1. The D9 family is marked with one or two colored rings in the anode area.
2. KD102 diodes in the anode area are indicated by a colored dot. The case is transparent.
3. KD103 have a color body that complements the dot, with the exception of 2D103A, which is indicated by a white dot in the anode area.
4. The KD226, 243 families are marked with a cathode region ring. No other marks are provided.
5. Two colored rings in the cathode area can be seen in the KD247 family.
6. KD410 diodes are indicated by a dot in the anode area.

Other visible marks are present. You will find a more detailed classification by studying the publication of A.P. Kashkarov. On the labeling of radioelements. Beginners are concerned about the issue of determining the location of the cathode and anode.

1. You see: one side of the cylinder is equipped with a dark stripe - a cathode has been found. Colored may be part of the labeling discussed today.
2. If you know how to operate a multimeter, the anode is easy to find. An electrode where we will apply the red probe to open the valve (we will hear a bell).
3. The new diode is equipped with an anode antenna that is longer than the cathode.
4. Let's look through the glass body of the LED with a magnifying glass: the metal anode resembles the tip of a spear, smaller in size than the cathode.
5. Old diodes contained arrow markings. The tip is the cathode. Allows you to determine the direction of activation visually. Modern radio installers have to train their intelligence, visual acuity, and precision of manipulation.

Foreign products received a different designation system. When choosing an analogue, use special correspondence tables. For the rest, the import base differs little from the domestic one. Marking is carried out according to JEDEC standards (USA), European system (PRO ELECTRON). Colorful color code decoding tables are massively provided by online sources.

Color coding

SMD diodes

In the SMD version, the diode body is sometimes so small that there are no markings at all. The characteristics of the devices depend little on the dimensions. The latter greatly influence the dissipated power. A larger current flows through the circuit; a diode must be larger in size to remove the resulting heat (Joule-Lenz law). As written, the marking of an SMD diode can be:

1. Full.
2. Abbreviated.
3. Lack of markings.

SMD elements in the total volume of electronics occupy approximately 80% of the volume. Surface mounting. The invented method of electrical connection is as convenient as possible for automated assembly lines. The SMD diode marking may not match the contents of the case. With a large volume of production, manufacturers begin to cheat, putting inside something that is not at all what is marked with the symbol. A large number of inconsistent standards causes confusion in the use of microcircuit pins (for diodes - microassemblies).

Frame

The marking may include 4 digits indicating the housing size. They do not directly correspond to the dimensions, take a closer look at the question in GOST R1-12-0.062, GOST R1-12-0.125. For hobbyists who cannot afford to obtain regulations, it is easier to use reference tables. Let's keep in mind the fact: SMD cases can differ in small things from company to company, because each manufacturer tailors the element base to its own products. Samsung has one distance from the motherboard of the washing machine, LG has another. The dimensions of SMD housings will require different conditions, heat dissipation conditions, and other requirements will be met.

Therefore, when purchasing an element according to the numbers in the reference book, take additional measurements if this is important. For example, when repairing household appliances. Otherwise, the purchased diodes may not fit at their destination. Amateurs do not bother with SMD due to the apparent complexity of installation, but for craftsmen this is a common thing, since microelectronics is impossible without such a successful technology.

When choosing a diode, it is worth keeping in mind the fact: many cases are the same, but are marked differently. Some designations do not have numbers. Convenient to use search engines. The cross table of size correspondence shown is taken from the site selixgroup.spb.ru.

SMD diodes are often available in SOD123 package. If one end has a stripe of some color or embossing, then this is the cathode (the place where negative polarity needs to be applied to open the pn junction). If only the case has inscriptions, then this is the designation of the case. If there is more than one line, the one characterizing the shell is larger.

Item type and manufacturer

It is clear that the type of case is a secondary thing for the designer. Some heat is dissipated through the surface of the element. It is from this point of view that the diode should be considered. Other important characteristics are:

• Operating and reverse voltage.
• The maximum permissible current through the p-n junction.
• Power dissipation, etc.

These parameters for semiconductor diodes are indicated in reference books. Labeling helps you find what you need among mountains of waste paper. In the case of an SMD element, the situation is much more complicated. There is no unified notation system. At the same time it is easier - the parameters from one diode to another do not change too much. The power dissipation and operating voltage differ by and large. Each SMD element is marked with a sequence of 8 letters and numbers, and some of the acquaintances may not be used at all. This is the case with industry veterans, giants of the electronics industry:

1. Motorola (2).
2. Texas Instruments.
3. Now converted and partially sold to Siemens (2).
4. Maxim Integrated Product.

The mentioned manufacturers are sometimes marked with two letters MO, TI, SI, MX. In addition, a couple of letters address:

• AD – Analog Devices;
• HP – Hewlett-Packard;
• NS – National Semiconductors;
• PC, PS – Philips Components, Semiconductors, respectively;
• SE – Seiko Instruments.

Of course, the appearance of the case does not always make it possible to determine the manufacturer, then you need to immediately type the alphanumeric sequence into a search engine. Other examples have been noticed: the NXP diode assembly in the SOD123W package does not carry any information other than the line indicated above. The manufacturer considers the information provided sufficient. Because SOD itself stands for small outline diode. We’ll find more on the company’s official website (nxp.com/documents/outline_drawing/SOD123W.pdf).

Printing space is limited, which explains these simplifications. The manufacturer tries to make the marking process as minimal as possible. Laser or screen printing is often used. This will allow you to fit 8 characters in an area of ​​only 4 square millimeters (Kashkarov A.P. “Marking of radio elements”). In addition to those indicated for diodes, the following types of housings are used:

1. Cylindrical glass MELF (Mini MELF).
2. SMA, SMB, SMC.
3. MB-S.

To top it off, the same alphanumeric code sometimes corresponds to different elements. In this case, you will have to analyze the electrical circuit. Depending on the purpose of the diode, operating current, voltage, and some other parameters are assumed. According to the catalogs, it is recommended to try to determine the manufacturer, since the parameters have an insignificant scatter, making it difficult to correctly identify the product.

other information

In addition to those indicated, other information is sometimes provided. Batch number, release date. Such measures are taken to make it possible to track new product modifications. The design department issues corrective documentation with a number and date. And if the assembly shop needs to take a feature into account when working on the changes made, the craftsmen should read the markings.

If you assemble equipment according to new drawings (electrical diagrams), using old parts, the result will not be what was expected. Simply put, the product will fail; it is gratifying if the process turns out to be reversible. Nothing will burn. But the shop manager will probably get hit in the head; the product will have to be remade in terms of the unaccounted factor.

Except for diodes

A billion modifications of diodes have been created based on p-n junctions. This includes varicaps, zener diodes and even thyristors. Each family has its own characteristics; there are many similarities with diodes. We see three global views:

• today's outdated element base is relatively large in size, clearly visible markings formed by standard letters and numbers;
• glass cases equipped with color symbols;
• SMD elements.

Analogues are selected based on the conditions specified above: power dissipation, maximum voltage, current flow.

The designation of diodes by graphic elements is a conditional indicator of the characteristics that the device has. At the moment there are quite a lot of elements, their base is diverse. Therefore, the abbreviations differ as much as possible from each other.

Various diodes have complex graphic symbols, including tunnel diodes, zener diodes and others. There are now varieties that can resemble a discharge light bulb. Moreover, such LEDs light up, which helps a person become even more confused in their use.

Semiconductor diodes

Such devices are as simple as possible; they are known to a large number of radio amateurs. There is a cylindrical base, a disk shape, and diode symbols are marked on the legs. Labels are as clear and visible as possible. The color of the case does not play any role at all. Low power will be indicated by small size.

If we talk about a fairly powerful diode, then we are talking about the presence of a thread for a nut. As a rule, this is needed to mount the radiator. To carry out the operation of the cooling system, attachments are used. At the moment, power consumption is consistently falling, and accordingly, the dimensions of the housings of any device are decreasing. Thanks to this, glass can be used. Such material will be cheaper, stronger and much safer to use.

Marking

If we talk about the designation of diodes, then it should be said that in the first place there will be a letter or number that characterizes the material. These can be gallium, silicon, germanium and indium. Accordingly, the following letters (numbers) will be printed on the body: A (3), K (2), G (1), I (4). In second place will be the diode characteristic. It must be said that, as a rule, its decoding should be found in the instructions. The most popular designation is D. This means that the device is rectifier or impulsive type. In third place there will be a number that characterizes the scope of application of the diode. Numbers from 1 to 9 are used here. The minimum characteristic is 1 - low-frequency, which have a current below 0.3. Nine means impulsiveness, in which the carrier lifetime will be much lower than 1 ns. The development number may or may not be specified.

It should be noted that a denomination that has a single-digit number is always preceded by a zero. For example, batch 7 will be written as 07. The group number of manufacturers is usually indicated by a letter. Thanks to it, you can find out various properties and parameters of the device. It also indicates the voltage, current supplied, and so on.

Nuances

In addition to such diode designations, some graphical indicators are also used. Thanks to them, you can solve the problem and understand how high the operating point of the device is. Sometimes the diodes are marked with information about what production technique was chosen, what housing material is available, and the weight of the device. In principle, such information will be useful to those who create equipment; amateurs do not need such data.

It should be noted that imported manufacturers work according to a different scheme. The marking of a diode of this type will be quite simple; its meaning can be found in a special table. That is why analogues will be very easy to find.

Color coding

Many radio amateurs know that most diodes, unfortunately, are alike. However, it should be noted that some devices are still marked with special color markings, which make it possible to immediately identify such devices. If you look at the diode marking table, you can say that they are divided into 2 main types. We are talking about the designation of the anode and cathode, and manufacturers often replace the body color with a regular colored dot.

At first glance, you can distinguish any colored diodes, which will be discussed below.

For example, diodes of the KD410 family are distinguished by the fact that they have a point in the area of ​​​​the anode. The case is transparent for KD102 diodes. The KD274 device has two colored rings near the cathode. It should be noted that there are also other distinguishable marks that will make it easy to distinguish devices from each other.

Many beginners, when considering the types of diodes, unfortunately, cannot determine where the anode is and where the cathode is. It should be noted that new devices that are being created in modern times operate in such a way that the anode has a tendril slightly longer than the cathode. Also, if a person knows how to use a multimeter, he can easily distinguish the anode from the cathode. The cathode can also be found by a dark stripe when looking at the side of the cylinder. This is also color coded.

Foreign manufacturers have their own designation system. If you need to select an analogue, you should use correspondence tables. Otherwise, the characteristics of the devices do not differ from domestic ones. Color marking, as well as many other designations of diode parameters, as a rule, corresponds to either US standards or the European system.

SMD diodes

Unfortunately, when SMD devices are created, they are so small that markings are often not applied. It should be noted that the characteristics of such devices practically do not depend on their dimensions.

The only thing that needs to be specified is that the dimensions affect the power dissipation. In order for a large current to pass through the circuit, the diode must be large.

Nuances of marking SMD diodes

If we still consider devices that have a color designation, the following types of markings should be distinguished for diodes:

• full;
• abbreviated.

In electronics, unfortunately, SMD elements occupy about 80% of all devices. They can be surface mounted. Especially when it comes to automated assemblies, these devices are as convenient as possible.

It should be noted that often the markings do not correspond to the actual contents of the case. When a huge batch size is created, the manufacturer sometimes begins to cheat: the same characteristics are indicated, but the diode works in a completely different way. Due to such inconsistencies, there can be confusion when it comes to the use of the device in chips.

Frame

As for the housing, here the designation of semiconductor diodes, just like others, is unique. Four numbers are indicated that indicate the standard size. In general, they do not correspond to the dimensions in any way. If you want to know about this in more detail, then you need to refer to GOSTs. People who do not have the opportunity to work with regulations due to some nuances can use regular reference tables.

It should be noted that the housings of SMD devices may differ in small details from manufacturer to manufacturer. The fact is that any manufacturer creates a base for its equipment, and accordingly, some parts have to be changed.

Accordingly, the housing dimensions of the above-described SMD devices also need to be different; they must also fulfill other requirements for correct operation, such as heat dissipation conditions and so on. Therefore, before purchasing, you should not only be guided by the numbers in the directory, but also take measurements. Especially when it comes to repairing any equipment. Otherwise, such diodes may simply not be installed in the places where they are needed.

Additional Information

SMD devices are quite difficult to install, so many beginners do not risk working with them. However, craftsmen must be excellent at managing such electronics, since at the moment such devices are among the most popular among other types of diodes. You should also take into account that when choosing devices you need to look at their characteristics and external differences. Sometimes the cases are essentially the same, but the markings are different. Some symbols may not contain letters or numbers. Accordingly, it is necessary to have tables on hand that allow you to navigate this issue as much as possible. The rectifier diode designation can also be found in a similar reference table.

A diode usually refers to vacuum or semiconductor devices that pass alternating electric current in only one direction and have two contacts for inclusion in an electrical circuit. One-way conductivity of a diode is its main property. This property determines the purpose of the diode:

• conversion of high-frequency modulated oscillations into audio frequency currents (detection);
• rectification of alternating current into direct current.

Detection also means signal detection.

Classification of diodes

Based on the source semiconductor material, diodes are divided into four groups:

• germanium,
• silicon,
• from gallium arsenide,
• from indium phosphide.

Germanium diodes are widely used in transistor receivers, as they have a higher transmission coefficient than silicon.

This is due to their greater conductivity at a low voltage (about 0.1...0.2 V) of the high-frequency signal at the detector input and a relatively low load resistance (5...30 kOhm).

According to design and technological characteristics diodes are distinguished:

• point,
• planar.

By purpose semiconductor diodes are divided into the following main groups:

• rectifying,
• universal,
• impulse,
• varicaps,
• Zener diodes (reference diodes),
• stabilizers,
• tunnel diodes,
• reverse diodes,
• avalanche-span (ALD),
• thyristors,
• photodiodes, s
• LEDs and optocouplers.

Diodes are characterized by such main electrical parameters:

• current passing through the diode in the forward direction (direct current Ipr);
• current passing through the diode in the opposite direction (reverse current Irev);
• the highest permissible rectified CURRENT Ivypr.max;
• the highest permissible direct current Ipr.add.;
• direct voltage Unp;
• reverse voltage IOBR;
• highest permissible reverse voltage iobr.max
• capacitance CD between the diode terminals;
• dimensions and operating temperature range.

Old notation system

In accordance with the notation system developed before 1964, the abbreviated designation for diodes consisted of with two or three elements.

First element letter, D - diode.

Second element- number corresponding to the type of diode: 1...100 - point germanium, 101...200 - point silicon, 201...300 - planar silicon, 801...900 - zener diodes, 901...950 - varicaps, 1001...1100 - rectifying columns. Third element- a letter indicating the type of device. This element may be missing if there are no diode varieties.

Currently There is a notation system corresponding to GOST 10862-72. In the new, as in the old system, the following division into groups according to the maximum (limiting) frequency of amplification (current transmission) is accepted into:

• low-frequency LF (up to 3 MHz),
• midrange frequency (from 3 to 30 MHz),
• high frequency HF (over 30 MHz),
• ultra-high frequency microwaves;

By power dissipation:

• low-power (up to 0.3 W),
• average power (from 0.3 to 1.5 W),
• high (over 1.5 W) power.

New notation system

New diode marking system more perfect. It consists of four elements.

First element(letter or number) indicates the source semiconductor material from which the diode is made: G or 1 - germanium* K or 2 — silicon, A or 3 - gallium arsenide , And or 4 - indium phosphide.

Second element- a letter indicating the class or group of the diode.

Third element- a number that determines the purpose or electrical properties of the diode.

Fourth element indicates the serial number of the technological development of the diode and is designated from A to Z.

For example:

• diode KD202A stands for: K - material, silicon, D - rectifier diode, 202 - purpose and development number, A - variety;
• 2C920 - high power silicon zener diode of type A variety;
• AI301B is a gallium arsenide tunnel diode of the switching type B.

Sometimes there are diodes designated according to outdated systems: DG-Ts21, D7A, D226B, D18. D7 diodes differ from DG-Ts diodes in their all-metal housing design, as a result of which they operate more reliably in a humid atmosphere.

Germanium diodes of the DG-Ts21...DG-Ts27 type and diodes D7A...D7Zh, which are similar in characteristics, are usually used in rectifiers to power radio equipment from an alternating current network.

The diode designation does not always include some technical data, so you need to look for them in reference books on semiconductor devices.

One of the exceptions is the designation for some diodes with the letters KS or a number instead of K (for example, 2C) - silicon zener diodes and stabilistors.

After these designations there are three digits, if these are the first digits: 1 or 4, then taking the last two digits and dividing them by 10 we get the stabilization voltage Ust.

For example:

• KS107A - stabistor, Ust = 0.7 V,
• 2S133A - zener diode, Ust = 3.3 V.

If the first digit is 2 or 5, then the last two digits show Ust, for example:

• KS 213B - Ust = 13 V,
• 2C 291A - Ust = 91 V.

If the number is 6, then you need to add 100 V to the last two digits, for example: KS 680A - Ust = 180 V.

Diode marking

The diode body usually indicates the semiconductor material from which it is made (letter or number), type (letter), purpose or electrical properties of the device (number), the letter corresponding to the type of device, and the date of manufacture, as well as its symbol.

The diode symbol (anode and cathode) indicates how the diode should be connected on device boards. The diode has two terminals, one of which is the cathode (minus), and the other is the anode (plus).

A conventional graphic image on the diode body is applied in the form of an arrow indicating the forward direction; if there is no arrow, then a “+” sign is placed.

The flat terminals of some diodes (for example, the D2 series) are directly stamped with the symbol of the diode and its type. When applying a color code, a color mark, dot or stripe is applied closer to the anode (Fig. 1).

For some types of diodes, color markings in the form of dots and stripes are used (Table 1). Old types of diodes, in particular point diodes, were produced in glass and were marked with the letter “D” with the addition of a number and a letter indicating the subtype of the device. Germanium-indium planar diodes were designated “D7”.

Rice. 1. Applying a color code to the diodes.

Table 1 Color coding of semiconductor diodes.

* Body color is brown.

Literature: V.M. Pestrikov. Encyclopedia of amateur radio.

Despite the simple principle of the diode, there are many varieties of this device. Markings on the case help to distinguish them - color coding of diodes. It allows you to determine the desired device when purchasing, as well as correctly connect it to the circuit. However, the large number of diode categories and multiple symbol systems can easily be confusing.

Types of diodes

The main division of diodes occurs according to their type. There are three categories: material of manufacture, p-n junction area and purpose.

Material

To produce diodes, one of four initial semiconductors is used:

• germanium - in low-power and precision circuits, has a higher transmission coefficient;
• silicon - inexpensive and durable, resistant to temperature, but has lower conductivity;
• gallium arsenide – more expensive and more complex than silicon, high radiation resistance;
• indium phosphide - in LEDs and for operation at ultrahigh frequencies.

Each material in different systems has its own letter or number, which is indicated at the beginning.

Transition area

There are two options for the structural placement of the cathode and anode:

1. Point diode. One of the electrodes in the form of a narrow needle is fused into the crystal, forming a p-n boundary. It has a small area, which results in a high operating frequency. They are almost out of use due to low strength, vulnerability to overloads and low maximum current.
2. Planar diode. The transition area is larger - the contact passes over the area of ​​the semiconductor wafer connected to the crystal. They are distinguished by higher capacity, low noise level, and low voltage drop. An example is a Schottky diode.

In modern marking, separation practically does not occur - planar diodes are gradually replacing point diodes.

Subtype

The following designation depends on the purpose of the device. There is a classification of diodes used in different areas: tunnel, laser, varicaps, zener diodes. There is also a division within the subtype– already according to technical parameters:

• operating frequency;
• recovery time;
• forward and reverse current;
• permissible values ​​of reverse and forward voltage;
• temperature regime.

This results in a large number of possible combinations, hence the difficulty of creating a unified labeling system.

Marking of domestic diodes

Russian-made diodes were marked in their own way in different periods. The standard was constantly changing; three versions were developed before the modern system was approved. Low and high power diodes were labeled differently. Combinations of letters and numbers correspond to color symbols, according to the table.

Old notation system

The least informative marking, from the point of view of the modern variety of diodes, was used until 1964. It included only three elements:

• letter “D” – semiconductor diode;
• a number indicating the design features of the diode and its purpose;
• letter identifying the variety (if any).

All useful information was encoded in the second part - the serial number. For example, a number up to 200 meant that the diode was a point diode, from 200 to 400 - a planar diode; Zener diodes were assigned a value from 801 to 900 and so on. It was difficult to navigate such a system.

In 1964, the system was improved. At the beginning of the code, an indication of the material of manufacture was placed: 1, 2, 3 or G, K, A - for germanium, silicon and gallium arsenide, respectively. The next letter indicated the type of device:

• varicap – B;
• Zener diode - C;
• diodes with high operating frequencies - A;
• rectifiers and diode bridges - D.

Then came the serial number, but it already belonged to a specific subclass. This made it possible to divide, for example, a tunnel diode into several groups: generator (up to 299), switching (up to 399) and reverse (up to 499). At the same time, for zener diodes the number indicated the stabilization voltage. For example, 1C273 can be deciphered as follows:

• 1 – germanium;
• C – zener diode;
• 273 – low power, stabilization voltage – 73 V.

At the end there could be a letter indicating the type of device, as in the first version. This marking was more convenient, but technological progress and the emergence of new types of diodes required further refinement.

New notation system

For modern models of domestic diodes, a new marking principle is used, based on several industry standards. The designation of the semiconductor material and diode category remained unchanged. The changes affected the three-digit number that determines the operating principle.

It cannot be considered separately, since each type of diode requires a special division according to technical parameters. For example:

• pulse diodes - the first digit indicates the recovery time (from less than 1 ns to 500 or more);
• rectifiers – average value of forward current;
• Zener diodes - different power (from 1 to 3 - less than 0.3 W, from 4 to 6 - up to 5 W) and stabilization voltage (less than 10 V, up to 100, more than 100).

The following numbers, unlike the old system, indicate the development number - the characteristics of a particular diode are not included in them. If there is a further division within the diode class, the corresponding letter appears after the number.

Important! Depending on the purpose of the diode, the marking may contain additional elements, for example, a number on a packaged device that determines the design features.

Diodes from foreign manufacturers

A similar principle with some differences is used in the marking system for imported diodes. There are three standards:

1. JEDEC - American. Each diode is represented by a set of designations in the form 1NXY, where X is the serial number and Y is the modification. All devices have the first two symbols, so they are not taken into account in the color marking. Each number or letter has its own color, according to the table.
2. PRO-ELECTRON – European. The two letters at the beginning are the material and subcategory of the diode. The serial number can take the form of a value from 100 to 999 (household appliances) or with the addition of letters (Z10-A99), implying industrial use. Each of the values ​​is encoded into a color element.
3. JIS - Japanese. It is noticeably different from the previous ones - the functional type is indicated at the beginning: photodiode, conventional diode, transistor or thyristor. Then comes S - the designation of the semiconductor; the next letter is the type of device within the category, then the serial number and modification letter (one or two).

It is almost impossible to remember all the combinations. If you understand at least the basic correspondences, you will be able to understand the purpose of the diode much faster.

SMD diodes

The peculiarity of SMD diodes mounted directly on the surface of the boards is the impossibility of full marking due to their small size. Hence the unique identification system. Several ways to distinguish such diodes:

1. Pay attention to the shape of the housing. Each type has a characteristic appearance, for example, electrolytic capacitors are cylindrical, ceramic capacitors are parallelepiped-shaped.
2. Check the size chart. Usually these are four digits that indicate the dimensions of the resistor in inches.

Each type of case and purpose has its own designation system, which makes decoding inconvenient.

SMD diode polarity

The small size also does not allow for the usual visible polarity markings. When determining the cathode, the following is used:

• markings in the form of colored rings are applied to its side;
• some cases without color symbols have a groove on the cathode side;
• if a triangle is depicted on the case, its apex points to the negative pole.

This helps avoid confusion. Most often, in all marking systems, symbols are applied to the cathode side, this is also true for SMD elements.

LED markings

There are fewer difficulties in identifying LEDs. Each type has characteristic external distinctive features. There are two categories:

1. SMD LED color. In turn, they are divided into groups according to radiation: multi-color diodes, neutral, warm and cold white.
2. Element size. By analogy with foreign coding, 4 digits are used, which indicate the size in millimeters. 3014 – size 3 x 1.4 mm.

The number in front of the LED type means the quantity per 1 meter of strip. For devices with long leads enclosed in a plastic or glass case, a system of color elements is used, which can be found in the table.

Color rendering index CRI

One of the non-obvious parameters in the encoding is the CRI value, which determines how natural the glow looks. The average parameter is 100 - this is sunlight; a lower value applies to artificial light sources. Accordingly, the higher the CRI, the better.

In addition to identifying the right type of appliance in a store, color coding can be used for practical purposes. For example, knowing the location and color of the elements, you can calculate the resistance of the resistor. To do this, just enter the data in the online calculator form. Understanding marking systems makes it easier to use diodes correctly and solves many problems associated with choosing the right type of device.

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