Transistor and diode numbering

- the numbering or code systems used for transistors, diodes and FETs.

There are many thousands of different types of diode and transistor. These have different characteristics according to the way they are designed and made. Some may be intended for high power applications, like those used in power amplifiers of power supplies, whereas others may be intended for small signal applications where low current consumption is an issue. Other types of transistor may be required for radio frequency applications.

As there is a vast number of different types of transistor, each type is given a unique code so that it can be identified and identical ones bought. In this way it is possible to specify a specific type of transistor by using its type number or code.

Semiconductor numbering 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 both diodes and transistors. In fact there are two main semiconductor numbering schemes in use:

1. Pro-electron scheme   This diode and transistor numbering scheme was originated in Europe and is widely used for transistors developed and manufactured here.



2. JEDEC 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.

Using these diode and transistor numbering schemes it is possible to look at the part number and identify certain properties it will possess and what applications it may be used for. In particular, the Pro-electron diode and transistor numbering scheme makes it possible to broadly identify the capabilities of the transistor. For example parameters such as the transistor being intended for low frequency power, RF, etc can be determined.

The JEDEC semiconductor numbering system details far less, being intended to be purely a numbering system. From the number it can be determined how many PN junctions are in the device.

Pro-Electron Numbering or Coding System

This a BC107 is a low power audio transistor and a BBY10 is variable capacitance diode for industrial or commercial use.

JEDEC Numbering or Coding System

Thus a 1N4148 is a diode and a 2N706 is a transistor.

Summary