RS8521XF 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	OUT	output	Amplifier output. Rail-to-rail swing capable, typically within a few mV of either supply rail with a 10 kOhm load. Short-circuit current is approximately 25 mA typical.
2	V-	power_in	Negative supply rail. Ground in single-supply operation, or the negative rail for dual supplies. Absolute maximum V+ to V- is 7.0 V; operating range gives 2.5 V to 5.5 V total supply.
3	+IN	input	Non-inverting input. Rail-to-rail common-mode range from (V-)-0.1 V to (V+)+0.1 V. Input bias current is 10 pA typical (CMOS input). Input terminals are internally diode-clamped to the supplies.
4	-IN	input	Inverting input. Rail-to-rail common-mode range from (V-)-0.1 V to (V+)+0.1 V. Input bias current is 10 pA typical (CMOS input). Input terminals are internally diode-clamped to the supplies.
5	V+	power_in	Positive supply rail. Operating range +2.5 V to +5.5 V (absolute maximum 7.0 V V+ to V-). Bypass with a 0.1 uF capacitor placed close to the pin per layout guidelines.

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.

RS8521XF
RS8521XFXK
RS8521XFXM
RS8522XK
RS8522XM
RS8523XN
RS8524XP
RS8524XQ

CAD (KiCad official)

Symbol: RS8521XF
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
`rs8521xf.step`	85 KB	You want the bare part, or you mark your own boards.
`rs8521xf-etched.step`	1.8 MB	You want the part with `RS8521XF` 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 15342dc49863196c, 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