Transistor Marking Code

Transistor is a semi conductor device which is made as a separate electronic component or as part of integrated circuits. These are made from Silicon or Germanium material. Majority of transistors are Silicon types and they can tolerate high temperature.
Transistors may be Bipolar or Field effect transistor. Information for a particular transistor is shown as a code on the body of the transistor.

Transistor marking code examples

Information for a particular transistor is shown as a code on the body of the transistor. According to the European system of coding, there are two alphabets before the number. First alphabet represents the type of semiconductor used and the second alphabet represents the use of transistor.

First letter
A – Germanium
B – Silicon
C – Gallium Arsenide
D – Indium Antimide

Second letter

C – Audio frequency Amplifier
D – Audio frequency power amplifier
F – Low power Radio frequency amplifier
P – High power Radio frequency amplifier

Thus the transistor BC548 is

B – Silicon C – Audio frequency amplifier – Silicon Audio frequency Amplifier
BD 140 – B – Silicon, D- Audio frequency power amplifier
AD 140 – A – Germanium, D- Audio frequency power amplifier
AC 187 – A- Germanium, C- Audio frequency amplifier

According to the American system, the code begins with 2N followed by a number that indicates the time of design. A higher number indicates recent design.

Eg. 2N 2222A


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    Thanks a googal these data sheets are unobtainable for me and sweeping the Net give a lot of info but not in ways that are good for amateurs

  • Rkphadke

    Dear sir

    I am very much happy to have information from you regarding Transistor .Same way if you can please send the information on LED and how to use them on main supply

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