TRANSISTOR CODES

Transistor codes

There are three main series of transistor codes used in the UK:

• Codes beginning with B (or A), for example BC108, BC478
  
  The first letter B is for silicon, A is for germanium (rarely used now).
  The second letter indicates the type; for example C means low power audio frequency;
  D means high power audio frequency; F means low power high frequency.
  The rest of the code identifies the particular transistor.
  There is no obvious logic to the numbering system.
  Sometimes a letter is added to the end (eg BC108C) to identify a special version
  of the main type, for example a higher current gain or a different case style.
  If a project specifies a higher gain version (BC108C) it must be used,
  but if the general code is given (BC108) any transistor with that code is suitable.
  
• Codes beginning with TIP, for example TIP31A
  
  TIP refers to the manufacturer: Texas Instruments Power transistor.
  The letter at the end identifies versions with different voltage ratings.
  
• Codes beginning with 2N, for example 2N3053
  
  The initial '2N' identifies the part as a transistor and the rest of the code
  identifies the particular transistor.
  There is no obvious logic to the numbering system.