INA129U - ±18V Precision Instrumentation Amp | Texas Instruments
MPN: INA129U ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $6.95 | $6.95 |
| 10 | $6.25 | $62.50 |
| 100 | $5.4 | $540.00 |
| 500 | $4.85 | $2,425.00 |
| 1,000 | $4.35 | $4,350.00 |
INA129U Overview
An instrumentation amplifier is a specialized amplifier category that measures the voltage difference between two inputs while rejecting signals common to both nodes. INA129U belongs to the hierarchy instrumentation amplifier, differential amplifier, analog signal-conditioning IC, and power-management-independent semiconductor. Its three-op-amp topology provides high input impedance, precise differential gain, and improved common-mode rejection compared with a simple difference amplifier.
Key verified features include maximum offset voltage of 50 µV, maximum offset drift of 0.5 µV/°C, maximum input bias current of 5 nA, and differential input protection extending to ±40 V. The current-feedback input circuitry maintains useful bandwidth at higher closed-loop gains, including 200 kHz at a gain of 100. These characteristics make the device useful where small transducer outputs must be amplified accurately in the presence of a larger common-mode voltage.
The INA129 gain equation uses a 49.4 kΩ external resistor to support drop-in replacement with comparable instrumentation amplifiers. Gain accuracy depends on that resistor and associated layout parasitics, so designers should follow the manufacturer gain-setting guidance and preserve a symmetric input path. Low bias current is especially valuable for high-impedance sensor sources, while high CMR suppresses supply and ground disturbances that appear equally on both inputs.
Typical uses include bridge-transducer signal conditioning, isolated low-voltage sensing, current-shunt measurement, biomedical acquisition, industrial sensor interfaces, laboratory instrumentation, and portable diagnostic equipment. For these applications, the ±40 V protected inputs can reduce accidental overload risk, although external protection and supply limits still require validation.
The principal design consideration is keeping both input paths symmetric and placing the gain resistor close to the device. Incorrect Kelvin routing or unequal input impedance can degrade CMR and offset performance. The 8-pin SOIC also makes PCB assembly straightforward, while exposed thermal behavior and supply noise still require normal analog-layout practices.
This page consolidates verified manufacturer and distributor information, package details, purchasing context, applications, and replacement guidance. It also distinguishes explicitly supported drop-in candidates from parts that require engineering review, helping designers compare the INA129U with alternatives rather than treating them as automatic equivalents.
Drop-in alternatives for INA129U — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
INA128U
✅ Drop-In📋 Reference alternative (not in catalog)
COS129U
✅ Drop-In📋 Reference alternative (not in catalog)
INA129UA
✅ Drop-In📋 Reference alternative (not in catalog)
INA129U Maximum Ratings & Electrical Characteristics
| Product Type | Precision, low-power instrumentation amplifier |
| Architecture | Three-op-amp instrumentation amplifier |
| Supply Range | ±2.25 V to ±18 V |
| Maximum Supply | ±18 V |
| Gain-Bandwidth Product | 1.3 MHz |
| Bandwidth at G = 100 | 200 kHz |
| Maximum Offset Voltage | 50 µV |
| Maximum Offset Drift | 0.5 µV/°C |
| Maximum Input Bias Current | 5 nA |
| Minimum Common-Mode Rejection | 120 dB |
| Input Protection | ±40 V differential inputs |
| Gain Range | 1 to 10,000 |
| Gain-Setting Resistor | 49.4 kΩ reference resistor |
| Operating Temperature Range | -40°C to +85°C |
| Package | 8-pin SOIC |
| Circuit Count | 1 amplifier |
INA129U Pin Configuration
| Pin 1 | RG — Gain-set resistor connection; consult the manufacturer datasheet for the exact pin drawing |
| Pin 2 | IN- — Inverting input |
| Pin 3 | IN+ — Non-inverting input |
| Pin 4 | V- — Negative supply or ground connection, depending on supply configuration |
| Pin 5 | REF — Reference input for output-offset or level shift |
| Pin 6 | OUT — Amplified output |
| Pin 7 | V+ — Positive supply |
| Pin 8 | RG — Gain-set resistor connection; consult the manufacturer datasheet for the exact pin drawing |
Typical Applications
INA129U is suitable for 6 applications: Bridge Transducer Signal Conditioning, Low-Voltage Current-Shunt Measurement, High-Impedance Sensor Front Ends, Industrial Control and Sensor Interfaces, Biomedical and Diagnostic Acquisition, Portable and Battery-Powered Measurement.
Bridge Transducer Signal Conditioning
The INA129U is a strong fit for bridge outputs because its 120 dB minimum common-mode rejection suppresses common-mode excitation while the small differential bridge signal is amplified. The verified maximum offset voltage of 50 µV and maximum offset drift of 0.5 µV/°C help preserve accuracy near a narrow transducer baseline. Use the 49.4 kΩ gain-setting reference value and keep the two input routes symmetrical. The 1.3 MHz gain-bandwidth product and 200 kHz bandwidth at gain 100 provide adequate bandwidth for many temperature, pressure, and load-cell front ends.
Recommended
Low-Voltage Current-Shunt Measurement
The INA129U can amplify a small differential voltage across a current shunt while rejecting supply ripple and other common-mode disturbances. Its 120 dB minimum common-mode rejection is valuable when the shunt voltage is small relative to the power-rail voltage. The ±40 V differential input protection helps tolerate wiring transients, although external protection may still be required. Choose the gain resistor and filtering carefully to avoid excessive noise amplification, and verify that the selected gain preserves the required bandwidth.
Recommended
High-Impedance Sensor Front Ends
The 5 nA maximum input bias current of the INA129U makes it appropriate for many high-source-impedance sensor interfaces, including pressure, chemical, and resistive sensing networks. Low bias current limits the voltage error caused by sensor impedance, while the 50 µV maximum offset specification supports accurate extraction of small differential outputs. The input path still needs controlled leakage, guarded routing, and suitable filtering. Validate source impedance, settling time, and sensor-generated noise before fixing the gain and filter values.
Recommended
Industrial Control and Sensor Interfaces
The INA129U supports industrial measurement systems that combine a low-level differential signal with a substantially larger common-mode voltage. Its 120 dB minimum common-mode rejection helps preserve measurement integrity in systems where ground shifts and supply noise are present. The three-op-amp architecture and external gain resistor make it practical for programmable analog front ends. At the board level, isolate sensitive input traces from switching nodes and maintain equal input impedances so the amplifier's common-mode performance is realized in practice.
Recommended
Biomedical and Diagnostic Acquisition
The INA129U can be used in biomedical and diagnostic signal-conditioning paths when the source is differential and the required bandwidth is compatible with the 1.3 MHz gain-bandwidth product. Its low 5 nA maximum bias current and 50 µV maximum offset are useful for low-amplitude sensor signals, while 120 dB minimum common-mode rejection helps reject common-mode interference. These specifications do not establish medical certification or patient-safety compliance; medical designs require separate system-level validation, isolation, protection, and regulatory review.
Recommended
Portable and Battery-Powered Measurement
The INA129U is appropriate for portable measurement systems when low power and precision are both important. The Texas Instruments product page identifies the INA129 family as low-power instrumentation amplifiers, and the INA129U supports supplies down to ±2.25 V. Its 5 nA maximum input bias current can reduce loading from high-impedance sensors. Designers should still calculate the device quiescent current from the complete manufacturer data, select a suitable regulator, and account for battery-headroom limits at the ±18 V maximum supply.
Recommended
Recommended Products Summary
Engineering reference data for INA129U — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | INA128U | COS129U | INA129UA |
|---|---|---|---|---|
| Package | 8-pin SOIC | 8-pin SOIC | SOP-8 | SOIC-8 |
| Brand | Texas Instruments | Texas Instruments | COSINE | Texas Instruments |
| Amplifier Type | Precision, low-power instrumentation amplifier | Precision instrumentation amplifier | Precision instrumentation amplifier | INA129-family instrumentation amplifier |
Key Differentiators
- Explicitly verified precision specifications (vs INA128U)
- Input protection for measurement systems (vs INA129UA)
- Gain-setting compatibility (vs INA128U)
Design Notes
Do not treat the SOIC-8 footprint alone as proof of interchangeability. Verify the gain resistor connection, reference pin behavior, supply limits, input-protection rating, offset, bias current, and common-mode range against the official datasheet. The supplied cross-reference data confirms related parts, but it does not provide a complete manufacturer comparison for every candidate.
Route IN+ and IN- as a closely matched differential pair, keep both input impedances as equal as practical, and place the 49.4 kΩ gain-setting resistor close to the gain connection. Avoid placing sensitive input traces beneath switching nodes or adjacent to high-current return paths. Symmetrical layout helps the specified 120 dB minimum common-mode rejection translate into system performance.
The INA129U accepts supplies up to ±18 V, while its differential input protection extends to ±40 V. These are separate limits: input protection does not permit the supply rails to exceed the rated range. Confirm single-supply versus dual-supply wiring, reference-pin configuration, input common-mode limits, and supply bypassing against the manufacturer datasheet before energizing a new board.
Choose the closed-loop gain and filtering together rather than maximizing gain without checking bandwidth. The verified data lists a 1.3 MHz gain-bandwidth product and 200 kHz bandwidth at gain 100. Excess gain can amplify sensor noise and reduce usable bandwidth, while input filtering can add phase shift. Evaluate the complete sensor, amplifier, protection, and ADC signal chain with the final source impedance and sampling rate.
Compliance Information
The supplied verified data does not state RoHS, REACH, lead-free, halogen-free, conflict-minerals, or automotive qualification status. No compliance claim is inferred.