BFG540 from Slkor SLKORMICRO Elec, in a SOT-143-4. Pinout and pin descriptions extracted from the manufacturer datasheet by ds2sf; symbol, footprint, and 3D from KiCad-official CAD.

Pinout

Pin	Name	Type	Function
1	C	passive	Collector of NPN transistor. Wide collector lead per SOT143B package. Max IC=120mA, BVCEO=15V, BVCBO=20V.
2	B	passive	Base of NPN transistor. BVEBO=2.5V. Drives high-gain low-noise RF amplifier operation up to fT=9GHz.
3	E	passive	Emitter of NPN transistor. Shared with pin 4 (dual emitter leads for improved grounding/thermal performance in SOT143B).
4	E	passive	Second emitter of NPN transistor, tied internally to pin 3. Dual emitter leads reduce parasitic inductance for microwave LNA use.

Key specifications

Parameter	Value
Manufacturer	Slkor SLKORMICRO Elec
Package	SOT-143-4
Category	RF And Wireless
Pins	4

Ordering variants

Same part, different packaging or reel option.

BFG540
BFG540/X

CAD (KiCad official)

Symbol: BFG540
Footprint: Package_TO_SOT_SMD:SOT-143
3D model: SOT-143-4 (KiCad packages3D, STEP)

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

Datasheet: Slkor SLKORMICRO Elec datasheet (5 pp, sha256 5b47e88954dfd847, retrieved 2026-08-17, tier: lcsc)
Datasheet language: Chinese. Pin names, descriptions, and specs on this page were extracted and translated to English by ds2sf; the linked PDF is the manufacturer original.
Extractor: ds2sf (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF