I have a SOT-23 SMD component marked \$\underset{\bullet}{\vert}3\bar{\textrm{S}}\;\bar{4}\$ as shown in the following images

Marking code pic 1

Marking code pic 2

I managed to find out that \$\textrm{3S}\$ stands for MMBT5551 NPN transistor. But I couldn't find the meaning of the prefix \$\underset{\bullet}{\vert}\$ and of the \$\bar{4}\$. I appreciate any help you can give me with it.

  • \$\begingroup\$ BTW, +1 for the excellent markup \$\endgroup\$ – Huisman Apr 19 '19 at 12:19

The bars on the top of the S and 4 mean "Non Lead-Free Marking".
Production year is 2005, week 4.

The dot of the \$\underset{\bullet}{\vert}\$ mark is the pin 1 marking (do check the datasheet, it has a pin numbering as well).

The combination of \$\underset{\bullet}{\vert}\$ means it was manufactured by a Philippine Subcontractor.

RoHS- Compliant Product Identification

| improve this answer | |
  • 1
    \$\begingroup\$ I knew the bars had to do with RoHS-Compliance (non compiance in this case). That's the way how I found the linked document. \$\endgroup\$ – Huisman Apr 19 '19 at 11:58

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.