PNDS / Marking codes / 3B

Identify an unknown SMD part: marking code “3B”

Packages rarely print the full part number. The marking below is shared by several part numbers — use the package, pin count and the manufacturer family together to narrow it down, then confirm against the datasheet.

25 candidates 15 with manufacturer source-traceable

Candidate part numbers

Part number	Manufacturer	Package	Mapping source
2SD2620J	ROHM ^*	SC-89 18ta - 3a Pan	Public marking directory
BC856B	NXP	SOT-23	Public marking directory
BC856BT	NXP	SOT-416	Public marking directory
BC856BT	PHI	SC-75/SOT416	Public marking directory
BC856BW	PHI	SOT-323	Public marking directory
BC856BW	DIODES	—	Public marking directory
BC857A	MCC	SOT-23	Public marking directory
CH450FPT	WCH ^*	SOT-323 16dc - 3a Chm	Public marking directory
FMMT918	FERRANTI	SOT-23	Public marking directory
MMBT918	FSC	SOT23	Public marking directory
R3111N131A	RICOH ^*	SOT-23-5	Public marking directory
RB461F	ROHM	SOT-323	Public marking directory
RH5RL23AA	RICOH ^*	SOT-89	Public marking directory
RN5RL23AA	RICOH ^*	SOT-23-5	Public marking directory
RQ5RW31AA	RICOH ^*	SOT-143R	Public marking directory
BC856BDW	—	SOT-323	Public marking directory
CMBT918	—	SOT-23	Public marking directory
MM3Z47V	—	SOD-323	Public marking directory
R1161D131A	—	—	Public marking directory
R3131N23EC	—	SOT-23	Public marking directory
R3132Q41EA	—	SOT-143	Public marking directory
RN5VD13CA	—	SOT-23-5	Public marking directory
TMPT918	—	SOT-23	Public marking directory
VD4	—	—	Public marking directory
VD5	—	—	Public marking directory

How we narrow this down

Package first — SOT-23 vs SOD-123 vs SC-59 eliminates most candidates immediately.
Pin count and body size — a 3-pin SOT-23 LDO cannot be a 6-pin dual transistor.
Marking style — laser-marked parts are usually newer production; ink marking often indicates older or second-source vendors.
Circuits around it — a part sitting on a rail with an inductor is a regulator, not a diode.
Datasheet check — every credible candidate lists its marking scheme in the “marking information” section.

FAQ

Same code, several parts — which one do I actually have? Compare package + pin count + surrounding circuit; if it still fits two parts, request a sample verification before production.
Can I substitute between the candidates? No — the same marking may sit on electrically different parts. Always match the electrical spec sheet, not just the marking.
Where do these mappings come from? Public SMD marking directories and historical stock tables; each row keeps its source so you can trace it.

Other codes starting with “3”

30 33 36 37 39 3A 3E 3D 32 35

Still not sure what the part is?

Send the code, package and a photo through the BOM hub — our engineers cross-check it against datasheets and sourcing records.

How these mappings are compiled: public SMD marking directories plus our own stock records. Each row keeps its original reference internally, so any mapping can be traced on request. ^* Manufacturer derived from the part-number family (some directory entries carry no manufacturer) — treat it as a lead, not a datasheet fact. Markings are indicative only — confirm with the physical batch marking and the original datasheet before ordering.