Texas Instruments INA111AU/1KE4

Overview

INA111AU/1KE4 from Texas Instruments (originally Burr-Brown) is a high-speed, FET-input instrumentation amplifier optimized for precision DC-coupled signal conditioning in noisy industrial and medical environments. It delivers 4µs settling time to 0.01% at G=100, 106dB minimum CMRR at G=100, ±500µV max input offset voltage, and operates from ±6V to ±18V supplies across –40°C to +85°C. It is used in bridge transducer amplification and high-impedance sensor front-ends.

For engineers reviewing the INA111AU/1KE4 datasheet, INA111AU/1KE4 pinout, INA111AU/1KE4 application, or INA111AU/1KE4 equivalent, key selection criteria include gain-setting resistor dependency (G = 1 + 50kΩ/RG), SOL-16 package thermal performance (θJA = 100°C/W), output sense pin requirement (Pin 12), and FET-input bias current (<20pA) enabling low-leakage transducer interfacing without external guard traces.

Technical Context

The INA111AU/1KE4 employs a current-feedback topology with three internal op amps (A1–A3) and laser-trimmed 25kΩ/10kΩ thin-film resistors, enabling 2MHz bandwidth at G=1 and 450kHz at G=100. Its differential input stage uses matched FET pairs to achieve <20pA input bias current and >10¹²Ω input impedance.

Unlike voltage-feedback instrumentation amplifiers, the INA111AU/1KE4 exhibits a predictable +6dB/octave gain rise near 2MHz due to an inherent response zero - not instability - and requires external RG for gain programming from 1 to 10,000. The SOL-16 package includes dedicated output sense (Pin 12), which must be connected to Pin 11 (VO) for stable operation, unlike the internally connected DIP version.

Key Specifications

Pinout & Package

SOL-16 surface-mount package (TI package code DW), 10.3mm × 7.5mm body, 1.27mm pitch, moisture sensitivity level 3 (260°C reflow, 168hr floor life). Pin 12 is output sense (VOSENSE); must be externally tied to Pin 11 (VO) for closed-loop stability.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD8421ARZ and INA128UA, the INA111AU/1KE4 uniquely combines current-feedback speed, FET-input leakage immunity, and dedicated output sensing - making it irreplaceable in high-accuracy, remotely loaded instrumentation loops where gain stability under load variation is non-negotiable.

Availability

INA111AU/1KE4 is available at Aetrix Electronics and suitable for medical instrumentation, industrial data acquisition, and precision transducer signal conditioning requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for INA111AU/1KE4 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 acquired Burr-Brown in 2000 and maintains its precision analog portfolio, renowned for high-accuracy data converters, amplifiers, and interface ICs serving industrial, automotive, and medical markets.

The INA111AU/1KE4 belongs to TI's legacy instrumentation amplifier product line, designed specifically for high-speed, low-drift DC signal conditioning in environments with severe common-mode noise and high source impedance.

FAQ

What is the function of Pin 12 (VOSENSE) on the INA111AU/1KE4?

Pin 12 is the output voltage sense terminal, required for closed-loop stability in the SOL-16 package. It must be connected directly to Pin 11 (VO) to close the feedback loop at the output pin. Unlike the DIP version, this connection is not internal - leaving Pin 12 floating causes gain inaccuracy and potential oscillation. The INA111AU/1KE4 relies on this external tie to maintain specified bandwidth and settling performance.

Can the INA111AU/1KE4 operate with a single supply?

No, the INA111AU/1KE4 is specified only for dual-supply operation from ±6V to ±18V. Its input common-mode range extends to ±12V and output swing to ±12.7V, both referenced to ground - it lacks rail-to-rail input/output capability or internal level-shifting circuitry needed for true single-supply use. Attempting single-supply operation violates absolute maximum ratings and results in saturation or damage.

What is the minimum recommended RG value for stable operation of the INA111AU/1KE4?

The minimum recommended RG is 49.9Ω, corresponding to G=1001. Lower values increase sensitivity to parasitic resistance (e.g., PCB trace, socket contact) and degrade gain accuracy. At RG < 10Ω, wiring resistance dominates the gain equation (G = 1 + 50kΩ/RG), causing unpredictable errors. For G ≥ 1000, use surface-mount metal-film resistors with <0.1% tolerance and low TCR, placed adjacent to Pins 4 and 6.

How does the INA111AU/1KE4 handle input overvoltage conditions?

The INA111AU/1KE4 inputs tolerate voltages from (V–) –0.7V to (V+) +15V. Internal clamp diodes protect against transient overvoltage if input current is limited to <1mA. For sources capable of >1mA, external clamping (e.g., 2N4117A diodes with series 10kΩ resistors) is required. Exceeding these limits risks permanent damage to the FET input stage, degrading bias current and offset specifications irreversibly.

Why does the INA111AU/1KE4 exhibit a +6dB/octave gain rise near 2MHz?

This rise is an inherent characteristic of its current-feedback topology - not instability - caused by a response zero in the transfer function. It is predictable and benign, confirmed by stable phase margin in all gain configurations. To flatten the passband, add a simple pole ≤700kHz (e.g., RC filter at the output). This behavior distinguishes the INA111AU/1KE4 from voltage-feedback IAs and enables wider usable bandwidth at unity gain.