INA118U/2K5 - Precision Low Power Instrumentation Amp | TI
MPN: INA118U/2K5 β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $4.2 | $4.20 |
| 10 | $3.95 | $39.50 |
| 100 | $3.76 | $376.00 |
| 500 | $3.55 | $1,775.00 |
| 1,000 | $3.3 | $3,300.00 |
Drop-in alternatives for INA118U/2K5 β same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
INA818AIDR
β Drop-Inπ Reference alternative (not in catalog)
INA128UA
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
INA129UA
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
INA111AU
β Drop-Inπ Reference alternative (not in catalog)
AD620AN
β Drop-Inπ Reference alternative (not in catalog)
INA118U/2K5 Maximum Ratings & Electrical Characteristics
| Amplifier Type | Instrumentation Amplifier |
| Number of Circuits | 1 |
| Input Offset Voltage (max) | 50 uV |
| Offset Drift (max) | 0.5 uV/degC |
| Input Bias Current (max) | 5 nA |
| Common-Mode Rejection Ratio (min) | 110 dB |
| Input Voltage Protection | +/-40 V |
| Supply Voltage Range (dual) | up to +/-18 V |
| Minimum Total Supply Voltage | 2.7 V (single supply, +/-1.35 V) |
| Quiescent Current | 350 uA |
| Gain Range | 1 V/V to 10000 V/V (single external resistor) |
| Bandwidth | 0.8 MHz at G = 1 |
| Bandwidth at G = 100 | 70 kHz |
| Operating Temperature Range | -40 degC to +85 degC |
| Package | 8-pin SOIC (D) |
| Mounting Type | Surface Mount |
| Packaging | Tape & Reel (2500 pieces) |
| RoHS Status | Compliant |
INA118U/2K5 Pin Configuration
| Pin 1 | RG β Gain resistor terminal A (connect external gain resistor to pin 8) |
| Pin 2 | IN- β Inverting differential input |
| Pin 3 | IN+ β Non-inverting differential input |
| Pin 4 | V- β Negative power supply (or GND in single-supply use) |
| Pin 5 | REF β Reference pin - drive with low impedance; output is referenced to this voltage |
| Pin 6 | OUTPUT β Amplifier output |
| Pin 7 | V+ β Positive power supply |
| Pin 8 | RG β Gain resistor terminal B (connect external gain resistor to pin 1) |
Safe Operating Area (SOA) & Thermal Characteristics
No official SOA curve available for this component. Always operate within absolute maximum ratings specified in the datasheet. Ensure adequate cooling and derate as needed.
Typical Applications
INA118U/2K5 is suitable for 6 applications: Thermocouple and RTD Temperature Measurement, Load Cell and Bridge Transducer Signal Conditioning, Medical Biopotential Acquisition (ECG/EEG), Industrial Process Control Analog Interfaces, Battery-Powered Portable Instrumentation, Test and Measurement Instrumentation.
Thermocouple and RTD Temperature Measurement
Thermocouple and RTD front ends demand high gain (100 to 500 V/V), microvolt-level offset, and strong rejection of ground noise. The INA118U/2K5 fits with 50 uV maximum offset and 0.5 uV/degC drift, so a type-K thermocouple signal (~41 uV/degC) is amplified without significant measurement error, while 110 dB minimum CMR rejects ground-potential differences in industrial environments. The current-feedback input circuitry preserves 70 kHz of bandwidth at G = 100, far more than needed for thermal time constants, ensuring no gain flatness issues. Wire the amplifier output to an ADC through a simple RC anti-alias filter, and reference the REF pin to mid-scale for single-supply designs.
Recommended
Load Cell and Bridge Transducer Signal Conditioning
Strain gauge and load cell bridges produce full-scale outputs of only a few millivolts, requiring gain of 100 to 1000 V/V with excellent CMR to reject excitation-ripple and ground noise. The INA118U/2K5 delivers 110 dB minimum CMR and a single-resistor gain setting (G = 1 + 50 kohm/RG, e.g. RG = 50 ohm for G = 1001), simplifying calibration. Its 5 nA maximum input bias current creates negligible bridge loading, and the +/-40 V input protection guards against miswiring of the excitation supply. Placing the gain resistor close to pins 1 and 8 and using a precision, low-TC resistor maintains gain accuracy across temperature.
Recommended
Medical Biopotential Acquisition (ECG/EEG)
ECG and EEG front ends require very high common-mode rejection because 50/60 Hz mains interference appears common-mode on body electrodes. The INA118U/2K5's 110 dB minimum CMR and 50 uV maximum offset directly address this: the amplifier suppresses mains pickup while faithfully amplifying the ~1 mV ECG signal at gains of 10 to 1000 V/V. The internal input protection to +/-40 V, combined with external series resistors, provides defibrillation-tolerant input protection, and 350 uA quiescent current suits battery-powered portable monitors. Driven-right-leg feedback can be implemented with a second amplifier referenced to the same REF node for further CMR improvement.
Recommended
Industrial Process Control Analog Interfaces
In process control, sensor signals travel long cable runs where ground potential differences can be volts; the INA118U/2K5's 110 dB minimum CMR and wide +/-18 V supply range make it ideal for extracting differential signals on +/-15 V analog rails. The 0.8 MHz bandwidth at G = 1 supports fast 4-20 mA loop monitoring and shunt-based current measurement, while the 350 uA quiescent current keeps self-heating low in densely packed I/O cards. Its SOIC-8 footprint suits standard industrial PCB assemblies, and the +/-40 V input protection tolerates field-wiring faults common in panel installations, reducing field-service damage rates.
Recommended
Battery-Powered Portable Instrumentation
Portable data loggers and handheld meters need precision amplification at minimal supply current. The INA118U/2K5 draws only 350 uA quiescent current and operates from a single supply as low as 2.7 V total, allowing direct operation from a 3 V lithium coin cell or two AA cells. The single-external-resistor gain setting saves board space and inventory, and the REF pin enables output level-shifting to mid-supply for fully unipolar operation. With 0.5 uV/degC maximum drift, measurements remain stable across the -40 degC to +85 degC range encountered outdoors, and the small SOIC-8 package conserves PCB area in compact enclosures.
Recommended
Test and Measurement Instrumentation
Bench instruments, data acquisition front ends, and sensor simulators require a precision differential input stage with switchable gain. The INA118U/2K5 supports gains from 1 V/V to 10000 V/V via one resistor (or a resistor network switched by an analog multiplexer), enabling programmable-gain front ends without sacrificing the 50 uV maximum offset accuracy. The current-feedback input stage maintains useful bandwidth at high gains (70 kHz at G = 100), so high-resolution DC and low-frequency AC measurements both perform well. The wide +/-18 V supply tolerance accommodates legacy +/-15 V instrument rails, and 110 dB CMR rejects noise from nearby switch-mode supplies in the chassis.
Recommended
Recommended Products Summary
Engineering reference data for INA118U/2K5 β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | INA818AIDR | INA128UA | INA129UA | INA111AU | AD620AN |
|---|---|---|---|---|---|---|
| Package | SOIC-8 | SOIC-8 - same | SOIC-8 - same | SOIC-8 - same | SOIC-8 - same | SOIC-8 - same |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Analog Devices |
| Input Offset Voltage (max) | 50 uV | 35 uV | 25 uV | 50 uV | [DATA_NEEDED] | 50 uV |
| Input Bias Current (max) | 5 nA | 0.5 nA | [DATA_NEEDED] | [DATA_NEEDED] | FET input, pA-level | [DATA_NEEDED] |
| Quiescent Current | 350 uA | 350 uA (same) | [DATA_NEEDED] | [DATA_NEEDED] | [DATA_NEEDED] | 690 uA |
| Gain Range | 1 to 10000 (single resistor) | 1 to 1000 | 1 to 10000 (single resistor) | 1 to 10000 (single resistor) | 1 to 1000 | 1 to 10000 (single resistor) |
| CMR (min) | 110 dB | [DATA_NEEDED] | 120 dB | 120 dB | [DATA_NEEDED] | 100 dB |
| Input Protection | +/-40 V | +/-40 V | +/-40 V | +/-40 V | [DATA_NEEDED] | +/-40 V |
| Price (qty 100, approx.) | $3.76 (as of 2026-09-13) | [DATA_NEEDED] | [DATA_NEEDED] | [DATA_NEEDED] | [DATA_NEEDED] | [DATA_NEEDED] |
Key Differentiators
- Constant bandwidth at high gain due to current-feedback input stage (vs AD620AN)
- Lower power than cross-brand equivalent (vs AD620AN)
- Direct upgrade path with better noise and bias current (vs INA818AIDR)
Design Notes
Place the gain-setting resistor RG directly across pins 1 and 8 with the shortest possible traces; long RG traces add series resistance that creates gain error and pick up noise. Use a 1% or better, low-temperature-coefficient resistor (e.g. 25 ppm/degC) for gain settings above 10 V/V. Keep the differential input traces to pins 2 and 3 symmetrical and guard them with ground pour to preserve CMR at high gains.
Never leave the REF pin (pin 5) connected directly to a resistor divider or long wire: its impedance appears in series with the output stage and directly degrades CMR, by roughly a factor proportional to the impedance ratio. Buffer the REF pin with an op amp or connect it straight to a low-impedance ground plane. Also remember the output cannot swing fully to either rail on single supplies - allow at least ~100 mV headroom near ground and V+.
Decouple both supply pins with 0.1 uF ceramic capacitors placed within a few millimeters of pins 4 and 7, plus a 1-10 uF bulk capacitor per board region. Although the INA118 draws only 350 uA, the current-feedback input stage is sensitive to supply transients, and long supply inductance can couple switching-regulator ripple into the output. On single supplies, ensure the input common-mode voltage stays within the specified linear range for the chosen gain and output swing.
For high-impedance sources or long cables, add series resistors and clamp diodes at pins 2 and 3 even though the inputs are internally protected to +/-40 V: the internal protection clamps conduct only above the fault threshold, and external series resistance (1 kohm to 10 kohm) limits fault current through the internal ESD structures. This is standard practice in ECG and industrial field-wiring front ends.
Compliance Information
Distributor listings (DigiKey, Mouser, LCSC) identify the part as RoHS-compliant surface-mount SOIC-8. Detailed REACH/halogen status per TI product page [DATA_NEEDED: REACH and halogen-free status].
