# INA121U

**Texas Instruments** · Instrumentation Amplifiers · SOIC-8

INA121U from Texas Instruments, in a SOIC-8. Pinout and pin descriptions extracted from the manufacturer datasheet (extract_pins, cross-checked by a second model); symbol, footprint, and 3D from KiCad-official CAD.

## Pinout

| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | RG | passive | Gain-setting resistor terminal; RG connects between pins 1 and 8 to set G = 1 + 50kΩ/RG (1 to 10,000 V/V), leave open for G = 1. |
| 2 | VIN- | power_in | Inverting input with internal over-voltage protection withstanding up to ±40V, and a ~4pA typical bias current that needs a return path. |
| 3 | VIN+ | power_in | Non-inverting input with internal over-voltage protection withstanding up to ±40V, and a ~4pA typical bias current that needs a return path. |
| 4 | V- | power_in | Negative supply, with total supply range ±2.25V to ±18V. |
| 5 | Ref | input | Output reference terminal, normally grounded, which must be a low-impedance connection to preserve CMR (8Ω in series degrades CMR to ~80dB at G = 1). |
| 6 | VO | output | Amplifier output referred to Ref, drives 1000pF capacitive load with ±14mA short-circuit current. |
| 7 | V+ | power_in | Positive supply, with total supply range ±2.25V to ±18V. |
| 8 | RG | passive | Gain-setting resistor terminal; RG connects between pins 1 and 8 to set G = 1 + 50kΩ/RG. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | Texas Instruments |
| Package | SOIC-8 |
| Category | Amplifiers/Comparators |
| Pins | 8 |

## CAD (KiCad official)

- Symbol: `INA121U`
- Footprint: `Package_SO:SOIC-8_3.9x4.9mm_P1.27mm`
- 3D model: SOIC-8 (KiCad packages3D, STEP)
- 3D model files: `ina121u-etched.step` / `ina121u-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `ina121u.step` / `ina121u.glb` are the bare package body.

## Provenance

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

- **Datasheet:** [Texas Instruments datasheet](https://www.ti.com/cn/lit/gpn/ina121) (22 pp, sha256 `df8d2ff139ef60c7`, retrieved 2026-10-07, tier: lcsc)
- **Extractor:** parts-factory `2.0.0` / `extract_pins 0.3`, primary `claude-haiku-4-5-20251001` (text), consensus `claude-sonnet-5-5` (agreed), guards: pin_guards 0.1: passed. Pins are checked against the footprint pad set and their cited datasheet pages before publish.
- **CAD:** KiCad official libraries (CC-BY-SA 4.0).

[Datasheet PDF](docs/ina121u-datasheet.pdf)