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Transistor Coding – The 4 Standard Coding Schemes

About Transistor Coding. One of the most common electronic components is a transistor. You will find it on almost all devices. But do you know that there are various transistor types? Also, what kind of transistor do you use on a simple circuit?

Identifying the transistor types can be quite confusing. However, if you understand the coding schemes of transistors, you can select the best for a particular circuit topology. 

Thus, our article will answer the various component questions of transistors by primarily explaining the transistor coding system. Join us as we delve into the basics of transistor coding. 


Pro-Electron or EECA Numbering Coding System


Several Transistors

Figure 1: Several Transistors


The EECA coding system represents the coding scheme adopted in European nations. It is designed to name the signal diode (s), bipolar transistors, and FETs. In our case, we'll look at how the system is useful in naming a signal transistor. 

According to this European naming system, two letters precede numbers in transistors.

The first letter of the code will represent the type of materials used to manufacture the transistor.

Here are the materials represented by the 1st letter in this naming system. Note, you'll find the letter B as the first letter in most codes for transistors. Thus, the most common transistor types are made of Silicon. 

First Letter Component type of Material
A Germanium
B Silicon
C Gallium Arsenide
D Indium Antimonide
R Compound Materials


A three-pin transistor

Figure 2: A three-pin transistor


Next, an additional letter gives further info on transistor coding. The second letter code for transistors represents the device application. Thus, from the second letter, you can identify the device type compatible with the type of transistor.

Here are the codes for the suffix letter. 

Second Letter Device Application
A Diode Radio Frequencies (RF)
B Variac
C Audio frequency amplifier, Transistor, Small frequency
D Audio frequency power amplifier, Power Transistor, 
E Tunnel diode
F Low power radio frequency amplifier
K Hall effect device 
L High-Frequency power transistor
N Optocoupler
P Devices that are sensitive to radiations
Q Devices that produce radiations
R Low power Thyristor
T Power thyristor
U Power thyristors for use in switching functions
Y In rectifiers
Z In Zener diodes or a voltage regulator diode

Third Letter


Additionally, the other important part of this transistor code system is the third letter. A transistor with the third letter is common in industrial/professional applications.  On the other hand, those without a letter are used in commercial applications. 

The third letters you'll find on transistors include W, X, Y, or Z. Lastly, and there is a serial number system that runs from 100-9999. Now that we know how the naming system works, we can assign a name to this transistor: AD 140

The A prefix means that the transistor is made of Germanium. 

The second letter, D, is used in the audio frequency power amplifiers.  


JEDEC Numbering or Coding System



Several Transistors

Figure 3: Several Transistors


The Joint Electron Device Engineering Council (JEDEC) is used for transistors and diodes naming in the US. Also, it is a simplistic naming system that takes a first number, second letter, serial number, and suffix format. 

The second letter in the JEDEC numbering will always be an 'N.' Also; you can also identify the number of legs on the transistor by adding one to the first letter. 

The serial numbers for this naming system also run from 100-9999. However, they don't say anything about the transistor. Still, you can use the serial numbers to identify when the transistor came into the market. 

Lastly, there is an optional suffix in this naming system. It will provide the gain (hfe) group of the component you are processing. The table below shows the gain groups for various suffixes in the JEDEC numbering system. 

Suffix Gain Group
A Low gain
B Medium gain
C High gain
No suffix Any gain

Gain grouping in transistors is important, especially in the selection process. Mostly, high gain transistors are more expensive than the low gain types. As a result, high volume users of transistors will significantly save on costs if they buy low gain transistors.

Note, there are no extra letters in this naming system after the gain grouping. The various transistors under the JEDEC system include 2N2221A, 2N3819, and 2N904.


JIS semiconductor device numbering scheme


A Coded Transistor

Figure 4: A Coded Transistor


The Japanese Industrial Standard of naming takes the format of a digit, two letters, a serial number, and an optional suffix. 

Again, adding one to the first number will give you the number of legs of the device. Next, the two letters represent the type and the area of application of the device. The table below elucidates the particular representations of the letters in this system. 

Letters Intended Application
SA PNP HF Transistor
SB PNP AF Transistor
SC NPN HF Transistor 
SD NPN AF Transistor
SE Diodes
SF Thyristors
SG Gunn diode 
SH Unijunction Transistor (UJT)
SM Triacs
SR Rectifiers
SS Signal diodes
ST Avalanche Diode
SV Varicaps 
SZ Zener Diodes

Thirdly, there are serial numbers in this naming system that run from 10 to 9999. Lastly, there are optional suffixes. They represent the various types of transistors approved for particular uses by Japanese companies. 

Also, note that the first digit in this naming system is a 2 for transistors and 1 for diodes.

Moreover, as you may have noted, the first letter in this naming system is an S. Hence, the first two letters in a transistor will be '2S'. 

Because the '2S' will be synonymous in all transistors, you can ignore it during writing. Thus, you can write a transistor coded as 2SA1187 as A1187. 


Manufacturer Numbers


Some manufacturers also have their unique naming system for transistors. Often, this is usually for commercial reasons and marketing. For instance, Motorola has transistors such as MJE, MJ, MPS, and MRJ.

Similarly, Texas Instruments have transistors codes such as TIP, TIPL, and TIS. 




The above coding systems are the universally accepted ways of naming transistors. We have provided an in-depth explanation of identifying transistors using the various systems. However, you might still find that there are a few things you don't understand. If that's your case, feel free to contact us