Texas Instruments INA118U/2K5

Overview

INA118U/2K5 from Texas Instruments is a precision, low-power instrumentation amplifier designed for high-accuracy signal conditioning in noisy industrial and medical sensor interfaces. 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 supply range, and 350 µA quiescent current - enabling battery-powered ECG and weigh-scale front-ends.

For engineers reviewing the INA118U/2K5 datasheet, INA118U/2K5 pinout, INA118U/2K5 application, or INA118U/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 INA118U/2K5 uses a three-op-amp architecture with JFET-input stages and internal 25 kΩ/40 kΩ resistor networks, enabling programmable gain from 1 to 10,000 via a single external RG resistor between pins 1 and 8. Its current-feedback topology sustains 70 kHz bandwidth at G = 100 and 7 kHz at G = 1000.

Input overvoltage protection operates independently per pin, clamping to ±40 V without damage and limiting input current to ~6 mA even with supplies off. The Ref pin sets output common-mode level, requiring low-impedance drive (<12 Ω) to maintain >100 dB CMR at high gain.

Key Specifications

Pinout & Package

INA118U/2K5 is packaged in an 8-pin SOIC (SO-8) with 3.91 mm × 4.90 mm body size, rated for –40°C to +125°C operation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with INA118U/2K5, INA828 offers improved noise and CMR for demanding medical sensing, while INA333 delivers superior drift performance in low-voltage portable systems - neither is pin-compatible, requiring layout revision, but both share identical gain programming methodology.

Availability

INA118U/2K5 is available at Aetrix Electronics and suitable for pressure transmitters, temperature transmitters, weigh scales, electrocardiogram (ECG) monitors, and analog input modules requiring stable component supply across industrial and medical production cycles.

Supply support for INA118U/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 leader specializing in analog and embedded processing technologies, with decades of expertise in precision signal chain solutions.

The INA118U/2K5 belongs to TI's precision instrumentation amplifier product line, engineered for high-accuracy sensor signal conditioning in industrial automation, test equipment, and medical diagnostics where low drift, high CMR, and robust input protection are critical.

FAQ

What is the maximum gain achievable with INA118U/2K5, and how is it set?

The INA118U/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 4.99 Ω (1%) with attention to parasitic resistance. At G = 1000, RG = 50.05 Ω (49.9 Ω standard value) achieves <0.1% gain error. The INA118U/2K5's laser-trimmed internal 50 kΩ network ensures gain accuracy remains within ±0.5% at G = 1000 across temperature.

Does INA118U/2K5 support single-supply operation, and what are the output swing limits?

Yes, the INA118U/2K5 operates from a single 4.5 V supply (V+ = 4.5 V, V– = 0 V). Under these conditions, the output swings from 60 mV (low) to 2.0 V (high) into a 10 kΩ load. The Ref pin defines the output common-mode level - grounding Ref yields rail-to-rail compatible output centered at 0 V, while biasing Ref to 2.5 V shifts output to 2.55–4.5 V range. Output swing degrades linearly below 4.5 V supply; operation below 4.5 V is not characterized and not recommended.

How does the input protection on INA118U/2K5 behave during overvoltage events?

The INA118U/2K5 features per-pin JFET-based protection that withstands ±40 V continuously, even with supplies disconnected. During overload, input current is limited to ~6 mA - sufficient to prevent damage without triggering latch-up. For example, applying –40 V to V– IN and +40 V to V+ IN causes no degradation. Protection remains active during power-down, making INA118U/2K5 suitable for hot-plug sensor interfaces. External series resistors are unnecessary and discouraged, as they degrade noise and CMR.

What is the bandwidth vs gain relationship for INA118U/2K5, and how does it impact sensor signal fidelity?

The INA118U/2K5 maintains 70 kHz bandwidth at G = 100 and 7 kHz at G = 1000, due to its current-feedback architecture. This enables accurate amplification of dynamic signals: a 1 kHz vibration waveform suffers <0.1 dB gain error and <1° phase shift at G = 100, while a 100 Hz ECG signal retains full fidelity even at G = 1000. Bandwidth rolls off at –20 dB/decade above cutoff; for G = 1000, small-signal settling to 0.01% takes 210 µs. These characteristics are fully specified in the SBOS027C datasheet across –40°C to +125°C.

Can INA118U/2K5 replace INA118P or INA118PB in existing designs?

Yes, the INA118U/2K5 is functionally and pin-compatible with INA118P (PDIP-8) and INA118PB (SOIC-8), sharing identical electrical specifications, pinout, and gain equation. All three variants meet the same 50 µV max VOS, 110 dB min CMR, and ±40 V input protection specs. The "U" suffix denotes SOIC packaging, "P" denotes PDIP, and "PB" denotes enhanced-grade SOIC; all operate over –40°C to +125°C. No layout or schematic changes are needed when substituting INA118U/2K5 for either variant in new production or repair scenarios.