BC556 BC557 BC558 BC559 SMD Equivalent

BC556/7/8/9 SMD Equivalent is BC856/7/8/9

The transistor part number nomenclature are JIS, Pro Electron, and JEDEC.

• IS is an acronym for Japanese Industrial Standard, and it is used in Japan,
• Pro Electron is a European standard.
• JEDEC is a North American standard developed in the United States that is also worldwide.

JEDEC is relatively user-friendly, SMD equivalent of 2N3904 is simply MMBT3904, 2N3906 is MMBT3906, and so on.

• MPSA05 (TO-92) MMBTA05 ( SOT-23 )
• MPSA55 (TO-92) MMBTA55 ( SOT-23 )
• MPSA06 (TO-92) MMBTA06 ( SOT-23 )
• MPSA56 (TO-92) MMBTA56 ( SOT-23 )
• 2N4401 (TO-92) MMBT4401 ( SOT-23 )
• 2N4403 (TO-92) MMBT4403 ( SOT-23 )
• 2N5551 (TO-92) MMBT5551 ( SOT-23 )
• 2N5401(TO-92) MMBT5401 ( SOT-23 )
• 2N3904 (TO-92) MMBT3904 ( SOT-23 )
• 2N3906 (TO-92) MMBT3906 ( SOT-23 )
• MPSA42 (TO-92) MMBTA42 ( SOT-23 )
• MPSA92 (TO-92) MMBTA92 ( SOT-23 )

Pro Electron is less user friendly, SMD equivalent of BC547 is not simply MMBT547.

a) There are some part numbers follow a system that BC8xx is an SMD version of BC5xx.

• BC546 (TO-92) BC846 ( SOT-23 )
• BC547 (TO-92) BC847 ( SOT-23 )
• BC548 (TO-92) BC848 ( SOT-23 )
• BC549 (TO-92) BC849 ( SOT-23 )
• BC556 (TO-92) BC856 ( SOT-23 )
• BC557 (TO-92) BC857 ( SOT-23 )
• BC558 (TO-92) BC858 ( SOT-23 )
• BC559 (TO-92) BC859 ( SOT-23 )

b) Some part numbers follow a system BC8_x is a SMD version of BC5_x.

• BC337 (TO-92) BC817 ( SOT-23 )
• BC338 (TO-92) BC818 ( SOT-23 )
• BC327 (TO-92) BC807 ( SOT-23 )
• BC328 (TO-92) BC808 ( SOT-23 )

IS system is a mess. Suppliers have no intent to make it systematic.

Some cross-reference suggests that the SMD versions of the 2SC1815 are available as the 2SC2712 (SOT-23), 2SC4738 (SOT-23), KTC3875 (SOT-23) and KTC3875S (SOT-23).

You have to compare the specifications in detail. Good luck!

Conclusion

Understanding the transistor nomenclature system will help you find the SMD version of a transistor much easier and much accurate.

The author was the global business manager of the Discrete division of National Semiconductor in Silicon Valley in the late ’80s.

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