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.

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

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.

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.