Transistor & Diode Numbering Systems & Codes

- the Pro-electron and JEDEC numbering systems or codes are the msot widely used for transistors, FETs and diodes, although for surface mount components much smaller codes are used to indicate which type of transistor diode of FET it is.

There are two main numbering systems for semiconductor diodes, transistors and FETs.

One numbering or code system is used more widely in Europe and the other in the USA.

The European based system is known as the Pro-electron system, sometimes also written as Proelectron system, and the one used more widely in North America is the JEDEC coding system.

The numbers using the Pro-electron and JEDEC systems have different formats as seen below:

Pro-Electron Numbering or Coding System


Pro-Electron Numbering or Coding System
for Diodes, Transistors and FETs
First Letter
Specifies semiconductor material
Second Letter
Specifies type of device
Subsequent Characters
  • A:Germanium
  • B:Silicon
  • C:Gallium Arsenide
  • R:Compound materials
  • 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
  • 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.

    From this it can be seen that a BC109 is a low power audio transistor and a BBY13 is variable capacitance diode for industrial or commercial use.


    JEDEC Numbering or Coding System


    JEDEC Numbering or Coding System
    for Diodes, Transistors & FETs
    First Number Second Letter Subsequent numbers
    1: Diode

    2: Bipolar transistor

    3: FET
    N Serial number of device

    Thus a 1N914 is a diode and a 2N706 is a transistor.

    By Ian Poole


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