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.
Numbering schemes
There are many different ways of having numbering systems. The first is that
each manufacturer gives each type of transistor that the company manufactures a
type number. This would lead to a huge number of different type numbers. There
would also be a huge overlap as different manufacturers made transistors that
were virtually the same. To overcome this problem, and to allow electronic
equipment manufacturers to be able to buy the same part from a number of
different manufacturers, there are international numbering schemes that have
been developed. One is known as the Pro-electron scheme and was originated in
Europe. The other is known as the JEDEC scheme and originated in the USA.
By looking at the transistor of diode type number, or code, to is possible to identify elements about it. The Pro-electron 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 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
First Letter Specifies semiconductor material |
Second Letter Specifies type of device |
Subsequent Characters | ||||||||||||||||||||||||||||||||||||||||||||||||
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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. |
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
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 2N3866 is a transistor.
Summary
The Pro-electron transistor and diode numbering or coding system provides more
information about the device, than the JEDEC system. However both 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.