PNDS / Marking codes / B9

Identify an unknown SMD part: marking code “B9”

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 14 with manufacturer source-traceable

Candidate part numbers

Part number	Manufacturer	Package	Mapping source
1SS311	TOS	SOT-23	Public marking directory
1SS397	TOS	SOT-323	Public marking directory
2SC4617	ON	SOT-416	Public marking directory
BZX399-C3V9	PHI	SOD-323	Public marking directory
BZX399-C3V9	PHI	SC-76/SOD323	Public marking directory
BZX399C3V9	PHI	SOD323	Public marking directory
BZX84C10	PHI	SOT-23 16dc - 3a Lge	Public marking directory
BZX884-C5V1	NXP	SOD-882	Public marking directory
MM5Z36V	FSC	SOD-523	Public marking directory
R3111N192A	RICOH ^*	SOT-23	Public marking directory
R3113D291A	RICOH ^*	—	Public marking directory
R3114Q261A	RICOH ^*	SC-82AB	Public marking directory
R5421N140C	RICOH ^*	SOT-23-6	Public marking directory
TC1015-3.6VRX	MIC ^*	SOT-23-5	Public marking directory
BZT52H-C4V3	—	SOD123F	Public marking directory
ELM9719NAB	—	SOT-89	Public marking directory
ELM9839AB	—	SOT-89	Public marking directory
IMB9A	—	SOT-23-6	Public marking directory
R1111N391A	—	SOT-23-5	Public marking directory
R1140Q291B	—	SOT-143R	Public marking directory
R1160D191A	—	—	Public marking directory
R1180Q291B	—	SC-82AB	Public marking directory
R3130N29EC	—	SOT-23	Public marking directory
RN5VD19AA	—	SOT-23-5	Public marking directory
RT9169-20CV	—	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 B3 B4 B5 B6 B7 B8 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.