Diode marking

Diode marking is a short graphical symbol for the element. The element base is currently so diverse, the cuts are very noticeable. It is difficult to identify a diode: zener diode, tunnel, Gunn. Released varieties resembling a discharge lamp. LEDs are lit, adding to the confusion.

Semiconductor Diodes

Perhaps the section is called somewhat trivial, when you just need to distinguish typical diodes from obsolete electronic tubes, the most up-to-date SMD modifications. Ordinary semiconductor diodes - easily solvable grief radio amateur. The side of the cylindrical body with a disk base, the legs contain an easily visible inscription painted with paint.

Semiconductor Resistors. Distinguish with the naked eye?

Case color does not matter, size indirectly indicates power dissipation. Powerful diodes often have a thread for a radiator mount. The result of the calculation of the thermal regime shows the lack of its own capabilities of the case, the cooling system is complemented by a hinged element. Today, power consumption drops, reducing the linear dimensions of the instrument cases. Specified allowed to use glass. New case material is cheaper, more durable, safer.

  • The first place is taken by the 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 diode or pulsed.
  • 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. Pulsed, recovery time over 500 ns.
  5. Pulsed, 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, lifetime of minority carriers below 1 ns.
  • The development number is two digits, it may be absent altogether. A par below 10 is padded to the left with zero. For example, 07.
  • The group number is denoted by a letter, it defines the differences of properties, parameters. The letter often becomes the key, indicates the operating voltage, direct current, etc.

In addition to labeling, reference books provide graphs for solving the problem of selecting the operating point of a radio element. Specify information about the production technology, material of the body, mass. Information helps the hardware designer, lovers of practical meaning is not.

Import notation systems differ from domestic ones, they are well standardized. Therefore, using special tables, it is easy to find suitable analogues.

color marking Every amateur radio operator knows the difficulty of identifying diodes surrounded by a glass case. On one face. At times, the manufacturer bothers to put clear marks, colored rings. According to the notation, three signs are introduced:

  1. Marks of cathode and anode regions.
  2. Case color, replaced by a color dot.

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

  1. The D9 family is marked with one or two colored rings of the anode region.
  2. Diodes KD102 in the anode area are indicated by a colored dot. The case is transparent.
  3. KD103 have a color-supplementing dot body, excluding 2D103A, indicated by the white dot of the anode area.
  4. Families KD226, 243 are marked with a ring of the cathode region. Other tags are not provided.
  5. Two colored rings in the cathode area can be seen in the KD247 family.
  6. Diodes KD410 indicated by a point in the anode.

Other distinguishable labels are present. A more detailed classification will find, having studied the edition of Kashkarov APBy marking radio elements. Beginners are concerned with the issue of determining the location of the cathode and the anode.

  1. You see: one side of the cylinder is provided with a dark stripe - a cathode was found. Colored may be part of the marking discussed today.
  2. Knowing how to exploit a multimeter, the anode is easy to find. Electrode, where we attach the red probe to open the valve( hear the bell).
  3. The new diode is equipped with the anode tendril longer than the cathode.
  4. We look through a magnifying glass through the glass case of the LED: a metal anode resembles a spear tip, smaller than the cathode.
  5. Older diodes contained a switch. The tip is a cathode. Allows you to determine the direction of inclusion visually. Modern radio installers have to train ingenuity, visual acuity, accuracy of manipulation.

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

Color marking

SMD diodes

In the SMD version, the diode package is sometimes so small that there is no marking at all. Characteristics of devices depend a little on dimensions. The latter strongly affect the power dissipation. The greater the current passes through the circuit, the diode must be large in size, which dissipates the arising( Joule-Lenz law) heat. According to the written SMD diode marking can be:

  1. Complete.
  2. Abbreviated.
  3. Lack of marking.

SMD elements in the total volume of electronics occupy about 80% of the volume. Surface mounting. The invented method of electrical connection is extremely convenient for automated assembly lines. The marking of the SMD diode may not coincide with the filling of the case. With a large volume of production, manufacturers begin to cheat, put inside not at all what is caused by a symbol. From a large number of uncoordinated standards, there is confusion about the use of microcircuit pins( for diodes - microassemblies).


Marking may include 4 digits indicating the size of the enclosure. Directly do not correspond to the dimensions, ask for more details in the GOST R1-12-0.062, GOST R1-12-0.125.For lovers who cannot afford to get regulations, it is easier to use reference tables. We keep in mind a fact: SMD cases from a company to a company can change little things, because each manufacturer podgadvaet element base for its own products. Samsung has one distance from the washing machine's motherboard, LG another. Dimensions of SMD packages will require different conditions of heat removal, other requirements are met.

Therefore, acquiring, according to the digits of the directory element, make additional measurements, if this is important. For example, when repairing household appliances. Otherwise, the purchased diodes may not get up at their destination. SMD lovers are not contacted due to the seeming complexity of installation, but for wizards this is common, since microelectronics is impossible without such a successful technology.

When choosing a diode, it is worth keeping in mind a fact: many cases are the same, but labeled differently. Some designations are devoid of numbers. Convenient to use search engines. The given cross-table of correspondence of standard sizes is taken from the site selixgroup.spb.ru.

Size Chart

SMD diodes are often manufactured in SOD123 packages. If there is a strip of any color or embossing on one end, this is the cathode( the place where you need to apply negative polarity in order to open the pn-junction).If only on the case there are inscriptions, then this is the designation of the case. If lines over one - characterizing the shell larger.

Element type and manufacturer

It is clear that the type of housing for the designer is secondary. Some heat dissipates through the surface of the element. From this point of view, it is necessary to consider a diode. In the rest of the important characteristics:

  • Operating and reverse voltage.
  • Maximum allowed current through pn-junction.
  • Power dissipation, etc.

These parameters for semiconductor diodes are indicated by references. Marking helps to find the right place among the mountain waste paper. In the case of an SMD element, the situation is much more complicated. There is no uniform notation. At the same time it is easier - the parameters from one diode to another do not change too much. Differ by and large power dissipation, operating voltage. Each SMD element is marked with a sequence of 8 letters and numbers, and some of the familiarity may not be used at all. This is the case with industry veterans, electronic industry giants: Motorola’s

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

The above-mentioned manufacturers are marked at times by two letters MO, TI, SI, MX.In addition, a couple of letters addresses:

  • 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 allow to determine the manufacturer, then in the search engine you need to immediately type the alphanumeric sequence. Other examples are noted: the NXP diode assembly in the SOD123W package does not carry any information other than the indicated line above. The manufacturer considers the information provided sufficient. Because SOD in itself is decrypted as a small outline diode. Others will find on the official website of the company( nxp.com /documents/ outline_drawing / SOD123W.pdf).

Space for printing is limited, and this simplification explains. The manufacturer tries to make it difficult to minimally mark itself. Often used laser or screen printing. This will allow to fit 8 characters in an area of ​​only 4 square millimeters( A. Kashkarov, "Labeling of radio elements").In addition to those indicated for diodes, the following types of enclosures are used:

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

To top it up, the same alphanumeric code sometimes corresponds to different elements. In this case, it is necessary 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 identify the manufacturer, since the parameters are not significant, making it difficult to correctly identify the product.

Other information

In addition to the above, other information is occasionally present. Batch number, release date. Such measures are taken, making it possible to track new product modifications. The design department issues corrective documentation with a number, date is present. And if the assembly workshop feature needs to be taken into account, practicing the changes made, the masters should read the markings.

If you assemble the equipment according to new drawings( wiring diagrams) using old parts, you will not get what you expected. Simply put, the product will be released into failure, it is gratifying if there is a reversible process. Nothing will burn. But the head of the shop will certainly get a hat, the goods will have to be redone in terms of the unaccounted factor.

In addition to

diodes Billion modifications of diodes were created on the basis of pn-junctions. These include varicaps, zener diodes and even thyristors. Each family has its own characteristics, with diodes there are many similarities. We see three global views:

  • , the outdated element base of relatively large size today, clearly distinguishable markings, formed in standard letters, numbers;
  • glass cases, equipped with color symbols;
  • SMD elements.

Analogs are selected on the basis of the conditions specified above: dissipation power, voltage limits, current flow.

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