Editing Pro Electron (section)

==Semiconductor diodes and transistors==

===The first letter gives the semiconductor type===
(see above)

===The second letter denotes the intended use===

{|class="wikitable"
|-
! 2nd letter !! Usage  !! Example
|-
|A||Low-power/small-signal diode || AA119, BA121
|-
|B||[[Varicap|Varicap diode]] ||BB105G
|-
|C||Small signal transistor, R<sub>thJC</sub>&nbsp;>&nbsp;15K/W || BC546C
|-
|D||High-power, low-frequency power transistor, R<sub>thJC</sub>&nbsp;≤&nbsp;15K/W || BD139
|-
|E||[[Tunnel diode|Tunnel (Esaki-)diode]] || AE100
|-
|F||Low-power, [[Radio Frequency|RF]] (high-frequency) [[BJT|bipolar]] or [[FET]], R<sub>thJC</sub>&nbsp;>&nbsp;15K/W || BF245
|-
|G||[[Hybrid integrated circuit|Hybrid device]] || BGY32, BGY585
|-
|H||[[Hall effect sensor]]/diode ||
|-
|L||High-frequency, high-power transistor (for transmitters), R<sub>thJC</sub>&nbsp;≤&nbsp;15K/W || BLW34
|-
|M||[[Ring modulation|Ring modulator]]-type [[frequency mixer]] ||
|-
|N||[[Opto-isolator]] || CNY17 
|-
|P||Radiation detector ([[photodiode]], [[phototransistor]])|| BPW34
|-
|Q||Radiation generator ([[Light-emitting diode|LED]])|| CQY99 
|-
|R||Low-power control or switching device: [[thyristor]]s, [[diac]]s, [[TRIAC|triac]]s, [[Unijunction transistor|UJT]]s, programmable unijunction transistors (PUT), silicon bidirectional switch (SBS), opto-triacs etc. || BR100 
|-
|S||Low-power switching transistor, bipolar or [[MOSFET]], R<sub>thJC</sub>&nbsp;>&nbsp;15K/W || BS170
|-
|T||High-power control or switching device: [[thyristor]]s, [[TRIAC]]s, silicon bidirectional switch (SBS), etc. || BT138 
|-
|U||High-power switching transistors, bipolar or [[MOSFET]], R<sub>thJC</sub>&nbsp;≤&nbsp;15K/W || BU508, BUZ11
|-
|V||[[Antenna (radio)|Antenna]] ||
|-
|W||[[Surface acoustic wave#Application in electronic components|Surface-acoustic-wave device]] ||
|-
|X||[[Frequency multiplier]]: [[varactor]], [[step recovery diode]] ||
|-
|Y||High-power rectifying diode || BY228 
|-
|Z||[[Avalanche diode|Avalanche]], [[Transient voltage suppressor|TVS]], [[Zener diode|Zener]] diode || BZY91 
|}

===The serial number===
Following these two letters is a 3- or 4-digit serial number (or another letter then digits), assigned by Pro Electron. It is not always merely a sequence number; there is sometimes information conveyed in the number:
* In early devices only, the serial number often indicated the case/package type (e.g. AF114-7 for TO-5 case, while AF124-7 were TO-72 versions of the same transistors); modern surface-mount devices often begin with "8",
* early silicon transistors followed the convention of using a middle digit of 0-5 for NPN and 6-9 for PNP. 
* the last digit often indicated a particular specification or application grouping, e.g. the AF117 and AF127 were similar IF amplifier devices in different cases; the BC109, BC149, BC169 and BC549 are similar low-noise transistors).
* some modern devices use letters, such as "B" to indicate HBT bipolar transistors.<ref name="D15/2010-07">{{cite web |url=https://www.eusemiconductors.eu/images/downloads/PRO%20ELECTRON_D15%20final%20version%202007_12%20ESIA%20updated%2016%2007%2010.pdf |title=European Type Designation Code System for Electronic Components |edition=16 |publisher=Pro Electron |place=Brussels, Belgium |date=July 2010 |access-date=2022-05-04 |archive-url=https://web.archive.org/web/20170714160626/http://www.eusemiconductors.eu/images/downloads/PRO%20ELECTRON_D15%20final%20version%202007_12%20ESIA%20updated%2016%2007%2010.pdf |archive-date=2017-07-14}}</ref>

===Suffixes and version specifiers===
Suffixes may be used, letters or perhaps blocks of digits delimited by "/" or "-" from the serial number, often without fixed meanings but some of the more common conventions are:
* for small-signal transistors "A" to "C" often means low to high h<sub>FE</sub>, such as in: BC549C<ref>[http://www.fairchildsemi.com/ds/BC/BC549.pdf Datasheet for BC549, with A,B and C gain groupings]</ref>),
* numeric suffixes may be used as an alternative way to show h<sub>FE</sub> (e.g. BC327-25), or voltage rating (e.g. BUK854-800A<ref>[http://www.datasheetcatalog.org/datasheet/philips/BUK854-800A.pdf datasheet for BUK854-800A (800 volt IGBT)]</ref>).
* for voltage reference diodes letters show the tolerance ("A","B","C","D","E" indicate 1%/2%/5%/10*/20%) and may be followed by the V<sub>z</sub> value, e.g. 6V8 for 6.8 Volts or 18V for 18 volts.
* "R" can mean "reverse polarity".

Examples of suffixes and manufacturers' extensions to the basic sequence number include:

{|class="wikitable"
|-
! Prefix class !! Usage  !! Example || Notes
|-
|AC||[[Germanium]] small signal transistor || AC127/01 || an AC127 (TO-1 case) with built-on heat-conducting block
|-
|AF||[[Germanium]] [[Radio Frequency|RF]] transistor || AFY40R || the "Y40" sequence number implies industrial uses, <br />the "R" indicates reduced specifications
|-
|BC||Silicon, small-signal transistor ("allround" or "G.P.") || BC183LB || the "L" indicates Base-Collector-Emitter pinout while <br />the "B" suffix indicates medium gain (240-500 h<sub>FE</sub>) selection
|-
|BC||Silicon, small-signal transistor || BC337-25 || -25 indicates an h<sub>FE</sub> of around 250 (140-400 range)
|-
|BD||Silicon Darlington-pair power transistor || BDT60B || the "B" suffix here indicates medium voltage (-100V<sub>CBO</sub>)
|-
|BF||Silicon [[Radio Frequency|RF]] (high-frequency) [[BJT]] or [[FET]] || BF493S || a BF493 with a -350V<sub>CEO</sub> rating
|-
|BL||Silicon high-frequency, high-power (for transmitters) || BLY49A || BLY49 in a TO-66 case
|-
|BS||Silicon switching transistor, bipolar or [[MOSFET]] || BSV52LT1 || SOT-23 (surface-mount) package
|-
|BT||Silicon Thyristor or TRIAC || BT138/800 || 800V-rated TRIAC
|-
|BU||Silicon high-voltage (for [[Cathode-ray tube|CRT]] horizontal deflection circuits) || BU508D || a BU508 with integral damper diode
|-
|BZ||Silicon regulator ("Zener") diode || BZY88-C5V6 || "C" indicates 5% tolerance, "5V6" indicates 5.6V<sub>z</sub>
|}

Note: A BC546 might only be marked "C546" by some manufacturers, thus possibly creating confusion with JIS abbreviated markings, because a transistor marked "C546" might also be a 2SC546.

Short summary of the most common semiconductor diode and transistor designations:
       BC549C
      / |--- \___ variant (A,B,C for transistors implies low, medium or high gain)
     /  |   \____ serial number (at least 3 digits or letter and 2 digits)
    /  device type:
 A=Ge     A=Signal diode
 B=Si     C=LF low-power transistor
          D=LF Power transistor
          F=RF transistor (or FET) 
          P=Photosensitive transistor etc.
          T=Triac or thyristor
          Y=Rectifier diode
          Z=Zener diode

===Usage in the Eastern Bloc===
Poland, Hungary, [[Electronics industry in the Socialist Republic of Romania|Romania]], and Cuba mostly used Pro Electron designations for discrete semiconductors just like Western Europe. Starting in 1971, in Poland the letter "P" was inserted, e.g. BUY54 became BUY'''P'''54.<ref>{{cite journal |author=Matuschek |title=Typenbezeichnungssystem für polnische Halbleiterbauelemente |trans-title=System of type designations for Polish semiconductor devices |language=de |pages=340 |journal=Radio Fernsehen Elektronik |publisher=VEB Verlag Technik |place=Berlin |issue=10 |year=1973 |volume=22 |issn=0033-7900}}</ref> [[Kombinat Mikroelektronik Erfurt]] (KME) in [[East Germany]] and [[Tesla (Czechoslovak company)]] used designations derived from the Pro Electron scheme. In particular, the first letter specifying the material differed while the second letter followed the table above (with the few exceptions for KME noted below).<ref name=tgl38015>{{cite book
|title=TGL 38015: Halbleiterbauelemente; Diskrete Halbleiterbauelemente und integrierte Halbleiterschaltkreise; Bildung der Typbezeichnung und Gestaltung der Typkennzeichnung
|trans-title=TGL 38015: Semiconductor Devices; Discrete Semiconductor Devices and Integrated Semiconductor Circuits; Formation of Type Designation and Marking
|publisher=Verlag für Standardisierung
|place=Leipzig
|language=de
|date=May 1986
|url=https://www.bbr-server.de/bauarchivddr/archiv/tglarchiv/tgl30001bis40000/tgl38001bis38500/tgl-38015-mai-1986.pdf
|access-date=2017-12-02
}}</ref>
{|class="wikitable"
|-
!Material
!1st letter Pro Electron
!1st letter KME East Germany
!1st letter Tesla
|-
|Germanium
|A
|G
|G
|-
|Silicon
|B
|S
|K
|-
|Compound materials (GaAs etc.)
|C
|V
|L
|-
|Multiple materials (e.g. Si + GaAs)
|C
|M
| —
|}

{|class="wikitable"
|-
!2nd letter
!KME East Germany usage
|-
|B
|Optoisolator (varicaps were included with other diodes under letter A)
|-
|M
|MOSFET (Pro Electron includes MOSFETs in letters C, D, F, L, S, U)
|-
|W
|Sensors other than radiation detectors
|}

Examples: [[Commons:File:GD241 Transistor.jpg|GD241C]] - Germanium power transistor from KME; [[Commons:File:Opto-isolator (aka).jpg|MB111]] - optoisolator from KME; [[KD503]] - Silicon power transistor from Tesla; [[Commons:File:Tesla LQ100.jpg|LQ100]] - LED from Tesla.