Transistor & Diode Part Numbering Codes

Pro-Electron, JEDEC & JIS are industry schemes for numbering semiconductor devices: diodes, bipolar transistors & FETs - they enable sourcing of devices from different manufacturers.

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There are many thousands of different types of diode, bipolar transistor and FET. These semiconductor devices have different characteristics according to the way they are designed and made.

As a result it is essential that the different semiconductor devices are given different part numbers to distinguish them from each other.

Initially manufacturers had to give their own numbers to devices, but soon standard part numbering schemes were used for semiconductor devices including diodes, bipolar transistors and FETs - both JFETs and MOSFETs.

Having industry standard numbering schemes for semiconductor devices has many advantages, not only for large scale manufacturers of electronic equipment right down to the hobbyist and student.

BC547 plastic leaded transistor: part number code indicates it is a silicon audio frequency low power transistor
BC547 transistor - BC in the part number indicates it is a silicon audio frequency low power transistor

Semiconductor device numbering / coding schemes

There are many different ways of organising a numbering scheme. In the early days of thermionic valve (vacuum tube) manufacture, each manufacturer gave a number to the types they manufactured. In this way there were vast numbers of different numbers for devices many of which were virtually identical. It soon became obvious that a more structured approach was required, so that the same device could be bought regardless of the manufacturer.

The same is true for semiconductor devices, and manufacturer independent numbering schemes are used for diodes, bipolar transistors and FETs. In fact there a few semiconductor numbering schemes in use:

  1. Pro-electron numbering scheme   This diode, bipolar transistor and FET numbering scheme was originated in Europe and is widely used for transistors developed and manufactured here.
  2. JEDEC numbering scheme   This diode and transistor numbering scheme was originated in the USA and it is widely used for diodes and transistors that originate from North America.
  3. JIS numbering scheme   This semiconductor device numbering system was developed in Japan and can be seen on diodes, transistors and FETs that are made in Japan.
  4. Manufacturers own schemes:   There are some devices, particularly specialised bipolar transistors and some FETs for which individual manufacturers may wish to retain all the manufacturing rights. They may not want to open up the specifications and manufacturing methods to others is they are using a technique they have developed. In these and similar instances, manufacturers will use their own part numbering schemes that do not conform to the industry standard schemes

The aim of the the industry standard numbering schemes is to allow for the identification and description of electronic components and in this case semiconductor devices including diodes, bipolar transistors and field effect transistors, to have common electronic components and component numbering across several manufacturers. To achieve this, manufacturers register a definition for new electronic components with the relevant agency and then receive a new part number.

This approach enables electronic equipment manufacturing companies to have second sources for their components and in this way assure the supply for large scale manufacturing and also to reduce the effects of obsolescence.

To varying degrees these numbering schemes allow for a broad description of the function of the diode, transistor or FET. The Pro-Electron scheme providing far more information than the others.

Pro-Electron or EECA Numbering Coding System

The Pro-Electron numbering scheme to provide a standardised scheme for semiconductor numbering - in particular diodes, transistors and fild effect transistors was set up in 1966 at a meeting in Brussels, Belgium.

The scheme for the numbering of semiconductor diodes, bipolar transistors and FETs was based around the format of the system developed by Mullard and Philips for thermionic valve or vacuum tube numbering that had existed since the early 1930s. In this the first letter designated the heater voltage and current, the second and subsequent letters the individual functions within the glass envelope and the remaining numbers indicated the valve based and the serial number for the type.

The Pro-Electron scheme took this and used letters that were seldom used for the heater descriptions to designate the semiconductor type and then used the second letter to define the function. Similarities existed between the valve / tube designations and those used for the semiconductor devices. For example, "A" was used for a diode, etc.

The scheme was widely used and in 1983 its management was taken over by the European Electronic Component Manufacturers Association, EECA.

First letter

  • A = Germanium
  • B = Silicon
  • C = Gallium Arsenide
  • R = Compound materials

Second letter

  • A = Diode - low power or signal
  • B = Diode - variable capacitance
  • C = Transistor - audio frequency, low power
  • D = Transistor - audio frequency, power
  • E = Tunnel diode
  • F = Transistor - high frequency, low power
  • G = Miscellaneous devices
  • H = Diode - sensitive to magnetism
  • L = Transistor - high frequency, power
  • N = Photocoupler
  • P = Light detector
  • Q = Light emitter
  • R = Switching device, low power, e.g. thyristor, diac, unijunction
  • S = Transistor - switching low power
  • T = Switching device, low power, e.g. thyristor, triac
  • U = Transistor - switching, power
  • W = Surface acoustic wave device
  • X = Diode multiplier
  • Y = Diode rectifying
  • Z = Diode - voltage reference

Subsequent characters

The characters following the first two letters form the serial number of the device. Those intended for domestic use have three numbers, but those intended for commercial or industrial use have letter followed by two numbers, i.e. A10 - Z99.


On some occasions there may be a suffix letter that is added:

  • A = low gain
  • B = medium gain
  • C = high gain
  • No suffix = gain unclassified

This is useful to both manufacturers and users because when transistors are manufactured, there is a large spread in the levels of gain. They can then be sorted into groups and marked according to their gain.

Using the numbering scheme it can be seen that a transistor with the part number BC107 is a silicon low power audio transistor and a BBY10 is silicon variable capacitance diode for industrial or commercial use. A BC109C for example is a silicon low power audio transistor with a high gain

JEDEC Numbering or Coding System

JEDEC, Joint Electron Device Engineering Council is an independent industry semiconductor engineering trade organisation and standardisation body. It provides many functions, one of which is the standardisation of semiconductor, and in this case, diode, bipolar transistor and field effect transistor part numbering.

The earliest origins of JEDEC can be traced back to 1924 when the Radio Manufacturers Association was established - many years later this became the Electronic Industries Association, EIA. In 1944, the Radio Manufacturers Association and the National Electronic Manufacturers Association established a body called the Joint Electron Tube Engineering Council, JETEC. This was set up with the aim of assigning and coordinating type numbers of electron tubes, (thermionic valves).

With the increasing use of semiconductor devices, the scope of JETEC was broadened and it was renamed JEDEC, Joint Electron Device Engineering Council in 1958.

Initial numbering of the semiconductor devices followed the broad outlines of the tube of valve numbering scheme that had been developed: "1" stood for "No filament / heater" and the "N" stood for "crystal rectifier".

The first digit for semiconductor device numbering was repurposed from indicating no filament to the number of PN junctions in the semiconductor device, and the numbering system was described in EIA/JEDEC EIA-370.

  • First Number =
    • 1 = Diode
    • 2 = Bipolar transistor or single gate field effect transistor
    • 3 = Dual gate field effect transistor
    The number equates to the number of junctions, although this has to be interpreted a little for MOSFETs.
  • Second Letter = N
  • Subsequent numerals = Serial number

Thus a device with the numbering code 1N4148 is a diode and a 2N706 is a bipolar transistor.

Sometimes extra letters are added to the part number and these often refer to refer to the manufacturer. M means the manufacturer is Motorola, while TI means Texas Instruments, although an A added to the part number often means a revision of the specification, e.g. 2N2222A transistors are widely available and these are an updated version of the 2N2222. Interpreting these numbers sometimes requires a little background knowledge.

JIS semiconductor device numbering scheme

The Japanese Industrial Standards, JIS part numbering scheme for semiconductor devices is standardised under JIS-C-7012.

This scheme uses a type number that comprises of a number followed by two characters and then this is followed by a serial number.

First Number

The first number indicates the number of junctions int he semiconductor device.

  • 1 = Diode
  • 2 = Bipolar transistor or single gate field effect transistor
  • 3 = Dual gate field effect transistor

Letters in positions 2 & 3

  • SA = PNP high frequency bipolar transistor
  • SB = PNP audio frequency bipolar transistor
  • SC = NPN high frequency bipolar transistor
  • SD = NPN audio frequency bipolar transistor
  • SE = Diodes
  • SF = Thyristor (SCR)
  • SG = Gunn devices
  • SH = UJT (Unijunction transistor)
  • SJ = P-channel JFET / MOSFET
  • SK = N-channel JFET / MOSFET
  • SM = Triac
  • SQ = LED
  • SR = Rectifier
  • SS = Signal diode
  • ST = Avalanche diode
  • SV = Varactor diode / varicop diode
  • SZ = Zener diode / voltage reference diode

Serial number

The serial number follows the first digit and the two semiconductor device type letters. The numbers run between 10 and 9999.


Following the serial number a suffix can be used to indicate the device has been type approved, i.e. there is a guarantee that it has been manufactured under the right conditions to produce the required semiconductor device.

Manufacturer numbers

Despite the fact that there are industry organisations in place to generate device numbers, some manufacturers wanted to produce devices that were unique to them. In some areas it would provide a device with a unique selling point that other manufacturers could not copy.

These semiconductor devices numbers are unique to the manufacturer and as a result they can be used to identify the source.

Some common examples are given below:

  • MJ = Motorola power, metal case
  • MJE = Motorola power, plastic case
  • MPS = Motorola low power, plastic case
  • MRF = Motorola RF transistor
  • TIP = Texas Instruments power transistor (plastic case)
  • TIPL = TI planar power transistor
  • TIS = TI small signal transistor (plastic case)
  • ZT = Ferranti
  • ZTX = Ferranti

The Pro-electron transistor and diode numbering or coding system provides more information about the device, than the JEDEC system. However both of these diode and transistor numbering schemes are widely used and enable the same device types to be made by a number of manufacturers. This enables equipment manufacturers to buy their semiconductors from a number of different manufactures and know that they are buying devices with the same characteristics.

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