Texas Instruments INA126E/250G4

Overview

INA126E/250G4 from Texas Instruments is a single-channel, micropower instrumentation amplifier optimized for precision low-level differential signal acquisition in battery-powered and space-constrained industrial systems. It delivers 250 μV maximum offset voltage, 3 μV/°C max offset drift, 35 nV/√Hz input voltage noise, ±1.35 V to ±18 V dual-supply operation, and 175 μA/channel quiescent current - enabling high-accuracy sensing in ECG front-ends and flow transmitters.

For engineers reviewing the INA126E/250G4 datasheet, INA126E/250G4 pinout, INA126E/250G4 application, or INA126E/250G4 equivalent, key selection considerations include its VSSOP-8 (DGK) package footprint, two-op-amp architecture for low power, gain-setting via external RG resistor (5–10,000 V/V), REF pin for output level-shifting, and guaranteed –40°C to +85°C industrial temperature performance.

Technical Context

The INA126E/250G4 implements a two-op-amp instrumentation amplifier topology that eliminates the third op-amp of traditional three-op-amp designs, reducing quiescent current to 175 μA while maintaining high common-mode rejection (80 dB min at G=5). Its internal laser-trimmed 40 kΩ/10 kΩ resistor network enables precise gain setting via a single external RG resistor with gain equation G = 5 + 80 kΩ/RG.

Input stage features balanced, high-impedance (≥1 GΩ) inputs with ±25 nA max input bias current and integrated diode-based input protection. The REF pin allows output DC level shifting - critical for single-supply operation - and must be driven by a low-impedance source (<8 Ω) to preserve CMRR. Output swing is specified as (V+) – 0.75 V and (V–) + 0.8 V under load.

Key Specifications

Pinout & Package

INA126E/250G4 is housed in an 8-pin VSSOP (DGK) package - 2.3 mm × 2.0 mm, 0.5 mm pitch - optimized for high-density PCB layouts and automated assembly. Thermal resistance R_θJA is 167.8 °C/W, requiring minimal copper area for thermal management in ambient temperatures up to +85°C.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar instrumentation amplifier applications.

Compared with AD8221ARMZ and INA333AIDRGT, the INA126E/250G4 offers the best balance of micropower operation, wide gain adjustability, and industrial temperature stability - making it optimal for portable medical and industrial sensor interfaces where design flexibility and supply voltage range are primary constraints.

Availability

INA126E/250G4 is available at Aetrix Electronics and suitable for ECG front-end amplifiers, pressure sensor signal conditioning, AC charging station current monitoring, and multiparameter patient monitor analog front-ends requiring stable component supply across long production lifecycles.

Supply support for INA126E/250G4 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor leader specializing in analog and embedded processing technologies, with decades of expertise in precision signal chain components.

The INA126 product line was designed specifically for low-power, high-accuracy instrumentation in portable and industrial measurement systems - emphasizing micropower consumption, wide supply range, and robust performance across temperature extremes.

FAQ

What is the maximum gain achievable with INA126E/250G4, and how is it configured?

The INA126E/250G4 supports gains from 5 V/V to 10,000 V/V using the formula G = 5 + 80 kΩ/RG. For maximum gain, connect a 7.87 Ω resistor between pins 1 and 8. At G=10,000, the device maintains ±1% gain nonlinearity and operates with ~2 kHz bandwidth. The internal 80 kΩ term derives from laser-trimmed metal-film resistors, ensuring stable gain accuracy across temperature. INA126E/250G4 requires no additional external components beyond RG for basic operation.

Can INA126E/250G4 operate from a single 3.3V supply, and what design considerations apply?

Yes, INA126E/250G4 supports single-supply operation from 2.7 V to 36 V. With a 3.3 V rail, configure the REF pin at 1.65 V (mid-supply) using a low-impedance divider or buffer to prevent CMRR degradation. Input common-mode range becomes limited to ~0.3 V to 2.9 V, and output swing reduces to ~0.4 V to 2.9 V. Avoid driving inputs beyond these bounds. INA126E/250G4's ±1.35 V dual-supply minimum translates to 2.7 V single-supply minimum, confirmed in Section 5.3 of the datasheet.

How does the REF pin function in INA126E/250G4, and why is low-impedance drive critical?

The REF pin sets the output DC level - VO = G·(V+IN – V–IN) + V_REF. Driving REF with >8 Ω series resistance degrades CMRR to ~80 dB (vs. 94 dB typical), due to impedance mismatch in the internal feedback path. Use an op-amp buffer (e.g., OPA333) or precision voltage reference with ≤1 Ω source impedance. INA126E/250G4's REF functionality enables single-supply compatibility and level-shifting without external summing amplifiers - a key differentiator versus fixed-reference IAs.

What is the input protection scheme of INA126E/250G4, and what are its absolute limits?

INA126E/250G4 integrates diode clamps from each input to V+ and V– rails, limiting input voltage to (V–) – 0.7 V and (V+) + 0.7 V. Absolute maximum input current is 10 mA - exceeded only if external series resistance is omitted during overvoltage events. For 24 V sensor interfaces, a 2.2 kΩ series resistor limits fault current to <10 mA. These protections are specified in Section 5.1 and validated per JEDEC JESD78 latch-up testing. INA126E/250G4 remains functional after transient overvoltage exposure within these bounds.

Does INA126E/250G4 require external capacitors for stability, and what layout practices improve performance?

No external compensation is needed - INA126E/250G4 is unity-gain stable and specified for CL ≤ 1000 pF. However, 0.1 μF ceramic decoupling capacitors are mandatory on V+ and V– pins, placed ≤2 mm from the DGK package. To minimize noise and crosstalk: (1) route differential inputs as tightly coupled, adjacent traces; (2) place REF trace over solid ground plane; (3) avoid routing RG or output traces parallel to noisy digital lines. These practices preserve the 35 nV/√Hz noise floor and 80 dB CMRR of INA126E/250G4.