PNDS / Marking codes / B3

Identify an unknown SMD part: marking code “B3”

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 23 with manufacturer source-traceable

Candidate part numbers

Part number	Manufacturer	Package	Mapping source
1PS301	NXP	SC-70	Public marking directory
1SS184	MCC	SC-59	Public marking directory
1SS184	MCC	SOT-23	Public marking directory
1SS301	TOS	SOT-323	Public marking directory
1SS361	TOS	SOT-23	Public marking directory
2SC4175-3	NEC ^*	SOT-323	Public marking directory
BD4727G	ROHM ^*	—	Public marking directory
BZX399-C2V2	PHI	SOD-323	Public marking directory
BZX399-C2V2	PHI	SC-76/SOD323	Public marking directory
BZX399C2V2	PHI ^*	SOD323	Public marking directory
BZX79-B2V7	PHI	SOD27 (DO35)	Public marking directory
FSS24	SANYO ^*	DO-214AA	Public marking directory
HSMS-2813	AGILENT	SOT-23	Public marking directory
HSMS-281E	AGILENT	SOT-323	Public marking directory
MBR0530	FSC	SOD-123	Public marking directory
MBRA130	ON ^*	—	Public marking directory
MMBD717L	MOT	SOT323	Public marking directory
R3111N132A	RICOH ^*	SOT-23	Public marking directory
R3113D231A	RICOH ^*	—	Public marking directory
R3114Q201A	RICOH ^*	SC-82AB	Public marking directory
R5421N131C	RICOH ^*	SOT-23-6	Public marking directory
RT9169-14CX	RICHTEK TECHNOLOGY, CORP.	SOT-89	Public marking directory
TC1015-3.0VRX	MIC ^*	SOT-23-5	Public marking directory
1SS361F	—	SOT-23F	Public marking directory
2SC1621-3	—	SOT-23	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 “B”

B1 B2 B4 B5 B6 B7 B8 B9 BA BB

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.