Pro Electron

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Pro Electron or EECA is the European type designation and registration system for active components (such as semiconductors, liquid crystal displays, sensor devices, electronic tubes and cathode ray tubes).

Pro Electron was set up in 1966 in Brussels, Belgium. In 1983 it was merged with the European Electronic Component Manufacturers Association (EECA) and since then operates as an agency of the EECA.

The goal of Pro Electron is to allow unambiguous identification of electronic parts, even when made by several different manufacturers. To this end, manufacturers register new devices with the agency and receive new type designators for them.

Designation system[edit]

Examples of Pro Electron type designators are:

Pro Electron took the popular European coding system in use from around 1934 for valves (tubes), i.e. the Mullard–Philips tube designation, and essentially re-allocated several of the rarely used heater designations (first letter of the part number) for semiconductors. The second letter was used in a similar way to the valves naming convention: "A" for signal diode, "C" for low-power bipolar transistor or triode, "D" for high-power transistor (or triode), and "Y" for rectifier, but other letter designations did not follow the vacuum tube mode so closely.

The three digits (or letter followed by two digits) after the first two letters were essentially a sequence number, with (at first) a vestige of the valve-era convention that the first one or two digits would indicate the base (package) type in examples such as in this family of general-purpose transistors:

Package NPN PNP
TO-18 BC10x BC17x
Lockfit BC14x BC15x
TO-92 BC54x BC55x

... where x may be:

  • 7 for high voltage
  • 8 for general purpose
  • 9 for low noise/high gain

Pro Electron naming for transistors and Zener diodes has been widely taken up by semiconductor manufactures around the world. Pro Electron naming of integrated circuits, other than some special (e.g. television signal-processing) chips, did not greatly take hold (even in Europe). Other popular designation systems were used for many integrated circuits.

Differences between Pro Electron and earlier valve-naming conventions[edit]

  • Unlike the tube naming convention, if there are two transistors in a single envelope, the type letter was never repeated - so a dual NPN RF transistor might get a type "BFM505" rather than something like "BFF505" for instance.
  • Although some of the most popular devices conform to a pattern of serial numbers that identified package type and polarity, many do not.
  • The letters assigned for the second character of transistor and diode type numbers differ in several ways, e.g.
    • "B" tends to be used for dual varicap diodes
    • "L" in the context of transistors designates RF power (transmitting) transistors; for valves it meant a high-power pentode tube (the usual choice for power RF)
    • "Z" is used for semiconductor Zener diodes instead of (full-wave) rectifier valves (tubes).

Frequently used first letters in European active devices[edit]

    • A Germanium (or any semiconductor with junctions in a material with a band gap of 0.6 to 1.0eV)
    • B Silicon (or band gap of 1.0 to 1.3eV)
    • C III-V semiconductors with a band gap of 1.3eV or more, like gallium arsenide in LEDs
    • D may be...
    • E (Mullard–Philips) tubes with a 6.3V heater
    • F Digital integrated circuits
    • P (Mullard–Philips) tubes for a 300mA series heater supply
    • R Devices without junctions, e.g. cadmium sulfide in a photoresistor
    • S Solitary digital integrated circuits
    • T Linear integrated circuits
    • U may be...
      • (Mullard–Philips) tubes for a 100mA series heater supply, or
      • Mixed digital/analogue integrated circuits

Electron tubes[edit]

   /  \ \\__ last digit(s) give serial number
  /    \ \__ first digit(s) indicate base (3=octal, 8 or 18 or 80=Noval (B9A), 9=Miniature 7-pin (B7G).
 /      \___ one letter per valve unit in the tube:
D=1.4v or less      A=single-diode (low power)
E=6.3v*             B=double-diode (usually shared cathode, but not always)
P=300mA             C=triode
U=100mA             F=pentode (low power)
                    L=pentode (high power)
                    Y=Single-phase rectifier
                    Z=Full-wave rectifier
* Note: some 6.3 volt heater types have a split heater allowing series (12.6 volt; the
  default for Noval pins 4 to 5) or parallel (6.3 volt) operation.

Semiconductor diodes and transistors[edit]

The first letter gives the semiconductor type[edit]

(see above)

The second letter denotes the intended use[edit]

2nd letter Usage Example
A Low-power/small-signal diode AA119, BA121
B Varicap diode BB105G
C Small signal transistor, RthG > 15K/W BC546C
D High-power, low-frequency power transistor, RthG ≤ 15K/W BD139
E Tunnel (Esaki-)diode AE100
F Low-power, RF (high-frequency) bipolar or FET, RthG > 15K/W BF245
G Hybrid device BGY32, BGY585
H Hall-effect sensor/diode
L High-frequency, high-power transistor (for transmitters), RthG ≤ 15K/W BLW34
M Ring modulator-type frequency mixer
N Opto-isolator CNY17
P Radiation detector (photodiode, phototransistor) BPW34
Q Radiation generator (LED) CQY99
R Low-power control or switching device: thyristors, diacs, triacs, UJTs, programmable unijunction transistors (PUT), silicon bidirectional switch (SBS), opto-triacs etc. BR100
S Low-power switching transistor, bipolar or MOSFET, RthG > 15K/W BS170
T High-power control or switching device: thyristors, TRIACs, silicon bidirectional switch (SBS), etc. BT138
U High-power switching transistors, bipolar or MOSFET, RthG ≤ 15K/W BU508, BUZ11
V Antenna
W Surface-acoustic-wave device
X Frequency multiplier: varactor, step recovery diode
Y High-power rectifying diode BY228
Z Avalanche, TVS, Zener diode BZY91

The serial number[edit]

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.[1]

Suffixes and version specifiers[edit]

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 hFE, such as in: BC549C[2]),
  • numeric suffixes may be used as an alternative way to show hFE (e.g. BC327-25), or voltage rating (e.g. BUK854-800A[3]).
  • 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 Vz 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:

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 RF transistor AFY40R the "Y40" sequence number implies industrial uses,
the "R" indicates reduced specifications
BC Silicon, small-signal transistor ("allround" or "G.P.") BC183LB the "L" indicates Base-Collector-Emitter pinout while
the "B" suffix indicates medium gain (240-500 hFE) selection
BC Silicon, small-signal transistor BC337-25 -25 indicates an hFE of around 250 (140-400 range)
BD Silicon Darlington-pair power transistor BDT60B the "B" suffix here indicates medium voltage (-100VCBO)
BF Silicon RF (high-frequency) BJT or FET BF493S a BF493 with a -350VCEO 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 CRT horizontal deflection circuits) BU508D a BU508 with integral damper diode
BZ Silicon regulator ("Zener") diode BZY88-C5V6 "C" indicates 5% tolerance, "5V6" indicates 5.6Vz

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:

     / |--- \___ 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[edit]

Poland, Hungary, Romania, and Cuba used Pro Electron designations for discrete semiconductors just like Western Europe. 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).[4]

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
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: GD241C - Germanium power transistor from KME; MB111 - optoisolator from KME; KD503 - Silicon power transistor from Tesla; LQ100 - LED from Tesla.

Integrated circuits[edit]

  • Linear ICs begin with the letter "T", e.g. TAA570 limiter–amplifier and FM detector.
  • Logic ICs begin with the letter "F".
  • Mixed analog/digital ICs begin with the letter "U", e.g. UAA180 LED bargraph A/D and driver.
  //  \ \__ serial number, gives the count and type of gates for example
 //    \___ H=gate ("Combinatorial circuit") J=flip-flop K=monostable Q=RAM R=ROM etc.

Unfortunately the serial number does not specify the same type of gate in each family, e.g. while an FJH131 is a quadruple 2-input NAND gate (like the 7400), an FCH131 is a dual 4-input NAND gate.[1]

See also[edit]


  1. ^ a b "European Type Designation Code System for Electronic Components" (PDF) (16 ed.). Pro Electron, Brussels, Belgium. July 2010. Retrieved 2018-02-06.
  2. ^ Datasheet for BC549, with A,B and C gain groupings
  3. ^ datasheet for BUK854-800A (800 volt IGBT)
  4. ^ TGL 38015: Halbleiterbauelemente; Diskrete Halbleiterbauelemente und integrierte Halbleiterschaltkreise; Bildung der Typbezeichnung und Gestaltung der Typkennzeichnung [TGL 38015: Semiconductor Devices; Discrete Semiconductor Devices and Integrated Semiconductor Circuits; Formation of Type Designation and Marking] (PDF) (in German). Leipzig: Verlag für Standardisierung. May 1986. Retrieved 2017-12-02.

External links[edit]