INA118UB - Precision Instrumentation Amp, 800kHz SOIC-8 | TI
MPN: INA118UB β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $22.81 | $22.81 |
| 10 | $21.5 | $215.00 |
| 100 | $19.8 | $1,980.00 |
| 500 | $18.2 | $9,100.00 |
| 1,000 | $16.9 | $16,900.00 |
Drop-in alternatives for INA118UB 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:
INA118U/2K5
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View Datasheet βINA118UBG4
β Drop-Inπ Reference alternative (not in catalog)
INA118U/2K5
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$3.3 / Unit
View Datasheet βINA818
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AD620ARZ
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View Datasheet βINA118UB Maximum Ratings & Electrical Characteristics
| Amplifier Type | Instrumentation Amplifier |
| Number of Circuits | 1 |
| Gain Bandwidth | 800 kHz (G = 1) |
| Slew Rate | 0.09 V/us |
| Input Offset Voltage (Max) | 50 uV |
| Supply Voltage Range | 1.35 V to 18 V (per rail) |
| Gain Range | 1 V/V to 10000 V/V, set by single external resistor |
| Operating Temperature Range | -40C to +85C |
| Package | 8-SOIC (0.154 in, 3.90 mm Width) |
| Mounting Type | Surface Mount |
| Architecture | 3-op-amp instrumentation amplifier |
| Grade | B (enhanced offset accuracy) |
INA118UB Pin Configuration
| Pin 1 | RG β Gain resistor terminal A |
| Pin 2 | -IN β Inverting input |
| Pin 3 | +IN β Non-inverting input |
| Pin 4 | V- β Negative supply (or GND in single-supply use) |
| Pin 5 | REF β Reference voltage for output offset shifting |
| Pin 6 | OUTPUT β Amplifier output |
| Pin 7 | V+ β Positive supply |
| Pin 8 | RG β Gain resistor terminal B |
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
INA118UB is suitable for 6 applications: Weigh Scale and Bridge Transducer Signal Conditioning, Thermocouple and RTD Temperature Front Ends, Medical ECG/EEG Biopotential Amplification, Industrial Data Acquisition and PLC Analog Inputs, Battery-Powered Portable Instrumentation, Current Shunt Measurement in Motor Drives.
Weigh Scale and Bridge Transducer Signal Conditioning
Strain-gauge bridges output only a few millivolts per volt of excitation at full load, so the front-end amplifier determines overall system accuracy. The INA118UB fits this role because its 50 uV maximum input offset (B grade) keeps offset-referred errors below one LSB of a 16-bit converter in many 3 mV/V full-scale designs, and its single-resistor gain setting lets one PCB support multiple load-cell capacities by changing RG. Placed directly after the bridge with the REF pin driven by a buffered divider or DAC for offset nulling, the amplifier converts the differential bridge signal to a ground-referenced output. Because gain drift is dominated by the external RG resistor, selecting a 10 ppm/C resistor preserves the 800 kHz-bandwidth part's precision over the industrial temperature range.
Recommended
Thermocouple and RTD Temperature Front Ends
Type K thermocouples generate roughly 41 uV/C, so even the amplifier's 50 uV offset represents about 1.2C of potential error - which is why the B grade's tight offset limit matters here. The INA118UB amplifies the microvolt-level thermocouple signal with gain typically around 100 V/V to 500 V/V set by RG, while its 800 kHz bandwidth is far more than the slow thermal signal requires, leaving margin for input filtering. Cold-junction compensation is implemented at the REF pin or in the ADC. For RTDs, the amplifier conditions the differential voltage across the sensor excited by a precision current source. The wide 1.35 V to 18 V rail range allows operation from single 3.3 V or 5 V supplies common in industrial temperature transmitters.
Recommended
Medical ECG/EEG Biopotential Amplification
Biopotential signals such as ECG (0.5 mV to 4 mV) and EEG (tens of uV) ride on common-mode mains interference that can exceed the signal itself by orders of magnitude. The INA118UB addresses this with the high CMRR of its 3-op-amp topology and 50 uV maximum offset, so small electrode offset and signal components are amplified without saturating the stage. Gains of 10 V/V to 100 V/V are typical in the first stage, followed by high-pass filtering to remove electrode half-cell offsets. The low power consumption of the INA118UB suits battery-powered patient-attached equipment, and the REF pin enables driven-right-leg style common-mode feedback. Designers must add patient isolation and comply with IEC 60601 at the system level.
Recommended
Industrial Data Acquisition and PLC Analog Inputs
Industrial analog input modules must amplify small differential sensor signals that share long cables carrying large common-mode noise from motors and switching loads. The INA118UB's 3-op-amp instrumentation topology rejects this common-mode voltage, while its +/-1.35 V to +/-18 V supply range matches both legacy +/-15 V PLC rails and modern single-supply designs. With gain set around 10 V/V to 100 V/V via a single RG resistor, signals from pressure transducers and flow meters are scaled to the 0 V to 5 V ADC input range. The -40C to +85C operating range covers cabinet-mounted industrial environments. Placing a small RC filter ahead of each input protects against ESD and RFI picked up on field wiring.
Recommended
Battery-Powered Portable Instrumentation
Portable measurement instruments demand amplifiers that extract small signals while drawing minimal supply current. The INA118UB's low-power INA118 core operates from supplies as low as 1.35 V per rail, enabling 3 V coin-cell or two-cell battery operation, and its low quiescent drain extends battery life compared to general-purpose op-amp-based discrete difference amplifiers. In handheld meters and dataloggers, a gain of 50 V/V to 1000 V/V via a single RG scales shunt or sensor voltages to the converter range. Because the gain-setting resistor dominates drift, low-drift thin-film RG values preserve accuracy over the full battery voltage and temperature excursion. The 8-SOIC package keeps the PCB footprint small for compact enclosures.
Recommended
Current Shunt Measurement in Motor Drives
Measuring DC bus or phase current through a low-side shunt requires amplifying tens of millivolts with accuracy, and the INA118UB's 50 uV offset keeps offset-referred error negligible even with a 10 mOhm shunt at light loads. Gain settings of 50 V/V to 100 V/V scale a 50 mV full-scale shunt drop to the ADC range, and the amplifier's bandwidth comfortably covers the control loop's requirements for drive current sensing. The differential inputs reject ground-bounce created by high motor currents returning through the power ground, which a single-ended op amp could not reject. The REF pin allows level-shifting the output to a mid-scale bias for bidirectional current measurement during regeneration.
Recommended
Recommended Products Summary
Engineering reference data for INA118UB β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | INA118U | INA118UBG4 | INA818 | AD620 |
|---|---|---|---|---|---|
| Package | SOIC-8 | SOIC-8 - same | SOIC-8 - same | SOIC-8 - same | SOIC-8 - same |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Analog Devices |
| Max Input Offset Voltage | 50 uV | Wider than B grade (see datasheet) | 50 uV | 35 uV | [DATA_NEEDED] |
| Bandwidth (G = 1) | 800 kHz | 800 kHz | 800 kHz | [DATA_NEEDED] | [DATA_NEEDED] |
| Slew Rate | 0.09 V/us | 0.09 V/us | 0.09 V/us | [DATA_NEEDED] | [DATA_NEEDED] |
| Input Bias Current | [DATA_NEEDED] | [DATA_NEEDED] | [DATA_NEEDED] | 0.5 nA max | [DATA_NEEDED] |
| Supply Voltage Range | 1.35 V to 18 V per rail | 1.35 V to 18 V per rail | 1.35 V to 18 V per rail | [DATA_NEEDED] | [DATA_NEEDED] |
| Grade / Positioning | B grade (enhanced accuracy) | Standard grade | B grade (identical) | TI upgraded successor | Cross-brand classic equivalent |
Key Differentiators
- Tightest offset grade in the INA118 SOIC-8 family (vs INA118U)
- Lower offset, bias current, and noise than the target part (vs INA818)
- Cross-brand substitution option with verification caveat (vs AD620)
Design Notes
Connect the RG gain resistor directly across pins 1 and 8 with the shortest possible traces and keep unrelated signals away from these nodes. Gain accuracy and drift of the INA118UB are dominated by RG, not the IC: use a 1% or better, low-TCR (10-25 ppm/C) thin-film resistor. Place a 0.1 uF ceramic decoupling capacitor at each supply pin (V+ pin 7, V- pin 4) within 2 mm of the pins, plus 10 uF bulk capacitance nearby for transient loads.
The REF pin (pin 5) must be driven from a low-impedance source - any series resistance between REF and its source degrades CMRR, since the REF pin gain is not unity. Buffer a resistor divider with an op amp (e.g., a precision op amp) or connect REF directly to ground for bipolar-supply designs. For single-supply bridge systems, use a buffered reference or DAC output to shift the output baseline and remove bridge offset.
Bandwidth scales inversely with gain in the 3-op-amp architecture: the 800 kHz figure applies at G = 1 only, so verify small-signal bandwidth at your actual gain before finalizing filter design. Also, inputs have bias-current return paths that must exist - never leave an input floating through a transformer or capacitor coupling without a DC return resistor. At high gains, keep source impedance balanced on both inputs to convert bias-current mismatch into a common-mode, rather than differential, error.
Compliance Information
Compliance data was not explicitly present in the provided web data; verify RoHS/REACH status on the TI product page or DigiKey listing before procurement.
