GS321-TR from Gainsil, 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 range extends 100mV beyond the supply rails (VSS-0.1V to VDD+0.1V). Absolute maximum input voltage is VSS-0.5V to VDD+0.5V.
2	VSS	power_in	Negative supply / ground reference. Total supply (VDD-VSS) rated 2.1V to 5.5V (absolute max -0.5V to +7.5V). Bypass to VDD with a 0.1µF ceramic capacitor for single-supply operation, or bypass to ground with 0.1µF for dual-supply operation.
3	IN-	input	Inverting analog input. Rail-to-rail common-mode range extends 100mV beyond the supply rails (VSS-0.1V to VDD+0.1V). Absolute maximum input voltage is VSS-0.5V to VDD+0.5V.
4	OUT	output	Rail-to-rail amplifier output. Swings to within <5mV of the rails at RL>100kΩ (30mV at 10kΩ). Typical short-circuit source/sink currents of 84mA/75mA at VS=5V.
5	VDD	power_in	Positive supply. Operating range 2.1V to 5.5V (absolute max +7.5V referenced to VSS). Place a 0.1µF ceramic bypass capacitor close to this pin for best performance.

Key specifications

Parameter	Value
Manufacturer	Gainsil
Package	SOT-23-5
Category	Op-amp/Cmp
Pins	5

Ordering variants

Same part, different packaging or reel option.

GS321-TR
GS321Y-TR
GS321-CR
GS321Y-CR
GS321-TRGS358-SR
GS321-TRGS358-MR
GS321-TRGS358-DR
GS321-TRGS358-FR
GS324-SR
GS324-TR

CAD (KiCad official)

Symbol: GS321-TR
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
`gs321-tr.step`	85 KB	You want the bare part, or you mark your own boards.
`gs321-tr-etched.step`	1.6 MB	You want the part with `GS321-TR` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 396 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: Gainsil datasheet (16 pp, sha256 3270b91a8ee80e05, 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