Texas Instruments INA118UB/2K5

Overview

INA118UB/2K5 from Texas Instruments is a precision, low-power instrumentation amplifier designed for high-accuracy signal conditioning of low-level differential sensor outputs in the presence of large common-mode voltages. It delivers 50 µV max input offset voltage, 0.5 µV/°C max drift, 110 dB min CMR at G = 1000, ±2.25 V to ±18 V dual supply operation, and 350 µA quiescent current-enabling use in battery-powered pressure transmitters and ECG front-ends.

For engineers reviewing the INA118UB/2K5 datasheet, INA118UB/2K5 pinout, INA118UB/2K5 application, or INA118UB/2K5 equivalent, this page provides verified technical context, gain-setting resistor design guidance, input protection behavior under ±40 V overload, output swing limits across supply voltages, and validated alternatives for precision analog signal acquisition.

Technical Context

The INA118UB/2K5 implements a three-op-amp architecture with JFET-input stages for low bias current (5 nA max) and integrated overvoltage protection that clamps input current to ~6 mA without damage. Its current-feedback topology sustains 70 kHz bandwidth at G = 100 and supports gain from 1 to 10,000 via a single external resistor between pins 1 and 8.

Laser-trimmed internal 50 kΩ resistors set the gain equation G = 1 + 50 kΩ/RG and contribute to 0.5 ppm/°C gain drift and ±0.5% max gain error at G = 1000. Input common-mode range is specified as (V–) + 2 V to (V+) – 2 V, with linear operation dependent on output swing constraints and reference pin impedance.

Key Specifications

Pinout & Package

INA118UB/2K5 is packaged in an 8-pin SOIC (SO-8) with 3.91 mm × 4.90 mm body size, optimized for surface-mount assembly and thermal performance (R_θJA = 115°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with INA118UB/2K5, INA818IDR offers superior DC precision for ultra-low-drift applications, while INA828IDR delivers lower broadband noise for dynamic signal fidelity-both retain identical pinout, gain equation, and supply compatibility for drop-in evaluation.

Availability

INA118UB/2K5 is available at Aetrix Electronics and suitable for pressure transmitters, ECG front-ends, and industrial weigh scales requiring stable component supply across extended production lifecycles.

Supply support for INA118UB/2K5 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 company specializing in analog and embedded processing technologies, with leadership in precision amplifiers and signal chain solutions.

The INA118UB/2K5 belongs to TI's precision instrumentation amplifier product line, engineered for high-accuracy, low-power sensor signal conditioning in industrial process control, medical diagnostics, and test equipment.

FAQ

What is the maximum gain achievable with INA118UB/2K5 and how is it set?

The INA118UB/2K5 supports gains from 1 to 10,000, set by a single external resistor RG connected between pins 1 and 8 using the equation G = 1 + 50 kΩ/RG. For G = 10,000, RG = 5 Ω is required; however, practical implementation uses nearest 1% standard values (e.g., 4.99 Ω). The INA118UB/2K5's laser-trimmed internal 50 kΩ resistors ensure gain accuracy remains within ±0.5% at G = 1000, making it suitable for calibrated measurement systems without trimming.

Does INA118UB/2K5 support single-supply operation and what are the output swing limitations?

Yes, the INA118UB/2K5 operates from a single 4.5 V supply (V+ = 4.5 V, V– = 0 V), with output swing specified as 1.8 V to 2 V (high) and 35 mV to 60 mV (low) at RL = 10 kΩ. This allows direct interfacing with 3.3 V or 5 V SAR ADCs when the Ref pin is biased at mid-supply. The INA118UB/2K5's output stage is not rail-to-rail; its swing is constrained by internal transistor saturation, so designers must verify headroom for full-scale signal capture in single-supply configurations.

How does the input protection in INA118UB/2K5 function during overvoltage conditions?

The INA118UB/2K5 incorporates JFET-based input protection that withstands ±40 V applied to either input-even with supplies disconnected-by limiting input current to approximately 6 mA. This behavior is confirmed in Figure 7-12 of the datasheet and eliminates need for external series resistors or TVS diodes in most industrial I/O applications. The protection operates independently of supply state, ensuring robustness during hot-plug or wiring fault events without degrading normal-signal noise performance.

What is the impact of reference pin impedance on common-mode rejection in INA118UB/2K5?

A high-impedance path to the Ref pin directly degrades CMR: a 12 Ω series resistance reduces typical CMR from 110 dB to ~80 dB at G = 1. The INA118UB/2K5 requires a low-impedance Ref connection-ideally driven by an op-amp buffer or tied directly to ground/mid-supply with short PCB traces-to maintain specified CMR performance. This dependency is critical in multi-channel systems where shared Ref routing introduces impedance mismatches that couple common-mode noise into the output.

Can INA118UB/2K5 replace INA118P or INA118PB in existing designs?

Yes, the INA118UB/2K5 is a direct replacement for INA118P (PDIP) and INA118PB (SOIC) variants, sharing identical electrical specifications, pinout, and gain equation. The "UB" suffix denotes SOIC packaging and "2K5" indicates 2.5 k-unit reel quantity; all versions meet the same 50 µV max offset, 110 dB min CMR, and ±40 V input protection specs. No layout or schematic changes are needed when migrating from INA118P or INA118PB to INA118UB/2K5, supporting seamless BOM consolidation.