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I've got a SOT-23 transistor (I think, but it could also be an IC) marked with 1E. Another one is marked with A7W. Then I can also see WR5. How are you supposed to decode these?

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    \$\begingroup\$ Do you know the manufacturer? \$\endgroup\$
    – Kevin Vermeer
    Nov 3, 2010 at 15:12
  • \$\begingroup\$ No idea on the manufacturer. \$\endgroup\$
    – Thomas O
    Nov 3, 2010 at 15:12
  • \$\begingroup\$ You can get some choices but it's hard to know for sure. 3 letters at 34 choices (I/1 and O/0 are too close) = "only" 39304 different parts, and I doubt there are fewer than 39304 different SOT-23 parts. \$\endgroup\$
    – Jason S
    Nov 11, 2011 at 16:59
  • \$\begingroup\$ Pls, whitch transistor has marking 3DG? (SOT 23, NPN, propably 400Vc-e) \$\endgroup\$
    – user26914
    Jul 30, 2013 at 13:06

3 Answers 3

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You could try the "SMD code book" or get the actual schematic or package for the device, but there may not really be a clear way to identify many SMD parts from the surface.

1E for example might be a plain BC847A according to the list.

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A bit late reaction, so I guess you've found out by now, but for completeness:

WR5 in SOT23 = BZX84-B6V2, 6.2V zener, by Philips

A7W in SOT23 = BAV99, dual diode, by Philips

1E in SOT23 = probably BC847A, NPN transistor, by Philips, but may also be either:
CM9NB847A, NPN transistor, by Canaan Microelectronics
FMMTA43, NPN transistor, by Zetex
KST43, NPN transistor, by Samsung
MMBTA43, NPN transistor, by ITT
R3131N29EC3, Vdet-IC 2.9V, by Ricoh
SMBTA43, NPN transistor, by Infineon
TMPTA43, NPN transistor, by Allegro

All found in the SMD databook 2011, 2500 comprehensive pages. Recommended.

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    \$\begingroup\$ Hmm, all the 43's look like drop-in replacements, and same with the 847A's. \$\endgroup\$
    – Mike DeSimone
    Nov 12, 2011 at 4:47
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    \$\begingroup\$ @Mike - yes, I thought they might be, but I didn't go and check the datasheets. That's why I list them as they appeared in the book. And highlighted the BC847, because that's a common one. \$\endgroup\$
    – stevenvh
    Nov 12, 2011 at 8:54
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    \$\begingroup\$ The 2010 version of the data book can be downloaded for free here. \$\endgroup\$
    – Federico Russo
    Jan 24, 2013 at 18:21
  • \$\begingroup\$ @FedericoRusso (and all who are about to click): 404 by now. \$\endgroup\$
    – Sz.
    Nov 6, 2015 at 13:53
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The A7W is a double diode. I took a guess and googled "transistor marking A7W". Good luck on the rest.

Here's a PDF that shows the markings for SMD Philips chips. Most are standard parts, so then you can look up a real datasheet.

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