RS321BXF from Jiangsu RUNIC Tech, in a SOT-23-5. 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	+IN	input	Non-inverting analog input. Rail-to-rail common-mode input range from -0.1V to (V+)+0.1V at Vs=5.5V. Typical input bias current 1pA.
2	V-	power_in	Negative supply rail. Tie to ground for single-supply operation, or to a negative rail for dual supply (V+ to V- must be 2.5V-5.5V, 7V absolute max). Bypass with 0.1uF close to the pin.
3	-IN	input	Inverting analog input. Same rail-to-rail input range and bias-current characteristics as the +IN pin.
4	OUT	output	Rail-to-rail amplifier output. Swings to within ~8mV of the rails with RL=10kΩ (26mV with RL=2kΩ). Typical short-circuit current ~54mA, slew rate 0.5V/us.
5	V+	power_in	Positive supply rail. Operating range 2.5V to 5.5V (referenced to V-), 7V absolute max. Bypass with a 10uF bulk cap and a 0.1uF ceramic close to the pin.

Key specifications

Parameter	Value
Manufacturer	Jiangsu RUNIC Tech
Package	SOT-23-5
Category	Op-amp/Cmp
Pins	5

Ordering variants

Same part, different packaging or reel option.

RS321BXF
RS321BXFXK
RS321BXFXM

CAD (KiCad official)

Symbol: RS321BXF
Footprint: Package_TO_SOT_SMD:SOT-23-5
3D model: SOT-23-5 (KiCad packages3D, STEP)

3D model downloads

Two STEP files. Same geometry, different body top:

File	Size	Use it when
`rs321bxf.step`	85 KB	You want the bare part, or you mark your own boards.
`rs321bxf-etched.step`	1.8 MB	You want the part with `RS321BXF` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 432 faces against 102 in the bare model. It survives export, section views, and rendering in any CAD tool, and it drops straight into KiCad or Fusion with no extra setup.

Provenance

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

Datasheet: Jiangsu RUNIC Tech datasheet (14 pp, sha256 b8add6ae05137706, retrieved 2026-08-17, tier: lcsc)
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