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Home > Products > Integrated Circuits (ICs) > Linear > Instrumentation, Op Amps, Buffer Amps

Texas Instruments INA125U/2K5

Name: INA125U/2K5
Brand: Texas Instruments
SKU: INA125U/2K5
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: INA125U/2K5

Manufacturer:: Texas Instruments

Category:: Instrumentation, Op Amps, Buffer Amps

Package:: 16-SOIC (0.154", 3.90mm Width)

Datasheet:: INA125U/2K5.pdf

Description:: IC INST AMP 1 CIRCUIT 16SOIC

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Product details

Overview

INA125U/2K5 from Texas Instruments (originally Burr-Brown) is a precision instrumentation amplifier with integrated voltage reference, designed for bridge sensor signal conditioning in industrial and battery-powered systems. It delivers 100 dB min CMR at G=100, 250 µV max input offset voltage, and selectable 2.5 V / 5 V / 10 V reference outputs - enabling direct excitation of strain gauge and RTD bridges.

For engineers reviewing the INA125U/2K5 datasheet, INA125U/2K5 pinout, INA125U/2K5 application, or INA125U/2K5 equivalent, key selection criteria include its single-resistor programmable gain (4–10,000), ±40 V input protection, sleep mode (±1 µA shutdown current), SO-16 package compatibility, and guaranteed operation from –40°C to +85°C.

Technical Context

The INA125U/2K5 integrates two high-precision op amps (A1 and A2) in a classic three-op-amp instrumentation topology, with laser-trimmed internal 60 kΩ gain-setting resistors and a dedicated bandgap-based reference amplifier. Its gain equation G = 4 + 60 kΩ/RG enables accurate, temperature-stable amplification without external trimming.

Reference functionality is implemented via four selectable output nodes (VREFBG, VREF2.5, VREF5, VREF10), each internally ratio-trimmed to ±0.5% initial accuracy and ±35 ppm/°C max drift. The SLEEP pin controls full analog shutdown, reducing quiescent current to ±1 µA while preserving high-impedance output state.

Key Specifications

Parameter	Value and Actual Design Meaning
Gain Range	4 to 10,000 V/V, set by single external resistor RG - eliminates need for matched resistor networks.
Input Offset Voltage	±250 µV max (initial), enabling sub-0.01% error in 10 mV full-scale bridge measurements.
CMR @ G=100	100 dB min - rejects common-mode noise from long sensor leads in factory automation environments.
Reference Accuracy	±0.5% max at 2.5 V / 5 V / 10 V outputs - supports ratiometric ADC conversion without external calibration.
Supply Range	Single: +2.7 V to +36 V; Dual: ±1.35 V to ±18 V - operates from coin cell (3 V) to industrial 24 V rails.
Sleep Current	±1 µA max at VSLEEP ≤ 100 mV - enables duty-cycled data acquisition in battery life–critical IoT sensors.
Input Protection	±40 V absolute max on VIN+ / VIN− - withstands ESD and wiring faults without external clamping diodes.

Pinout & Package

INA125U/2K5 is housed in a 16-pin SOIC (SO-16) surface-mount package per JEDEC MS-012, with 1.27 mm pitch and thermal resistance θ_JA = 100°C/W.

Pin/Terminal	Circuit Role	Design Meaning
1 (V+)	Positive power supply	Accepts +2.7 V to +36 V; powers all internal amplifiers and reference circuitry.
2 (SLEEP)	Shutdown control input	Logic-low (≤100 mV) disables amplifiers and reference; logic-high (>2.7 V) enables full operation.
3 (V−)	Negative power supply	Accepts −1.35 V to −18 V in dual supply; tied to ground in single-supply configurations.
4 (VREFOUT)	Reference output node	Connects to VREF2.5/VREF5/VREF10 pins to select 2.5 V/5 V/10 V excitation voltage for transducers.
5 (IAREF)	Instrumentation amp reference	Output common-mode reference point; must be low-impedance grounded to maintain >80 dB CMR.
6 (VIN−)	Inverting input	Differential input terminal; protected to ±40 V; requires bias current return path (e.g., matched resistors).
7 (RG)	Gain-setting resistor connection	Connects external RG between pins 7 and 8 to program gain per G = 4 + 60 kΩ/RG.
8 (RG)	Gain-setting resistor connection	Second terminal for RG; internal 60 kΩ resistor connects here to define gain slope.
9 (VO)	Amplifier output	Single-ended output referenced to IAREF; swings to within 0.8 V of V+ and 0.25 V of V−.
10 (VREF10)	10 V reference selection	Internally connected to reference amplifier; tie VREFOUT to this pin for 10 V bridge excitation.
11 (VREF5)	5 V reference selection	Internally trimmed 5 V node; used with VREFOUT for mid-range transducer excitation.
12 (VREF2.5)	2.5 V reference selection	Laser-trimmed 2.5 V output; optimal for low-voltage single-supply systems (e.g., +3.3 V or +5 V rails).
13 (VREFBG)	1.24 V bandgap reference	Unregulated 1.24 V ±0.5% output; usable when supply headroom is minimal (e.g., +2.7 V operation).
14 (VREFCOM)	Reference ground	Low-impedance return for reference current (180 µA typical); connect to system sensor common to avoid ground loops.
15 (VIN+)	Non-inverting input	Differential input terminal; identical protection and bias specs as VIN−; requires same bias current path.
16 (Sense)	Bridge sense feedback	Connects to bridge midpoint to enable 4-wire Kelvin sensing; improves accuracy by rejecting lead resistance errors.

Key Features

Feature	Design Value
Integrated precision reference	Four selectable outputs (1.24 V / 2.5 V / 5 V / 10 V) with ±0.5% accuracy - eliminates external reference IC and reduces BOM count.
Laser-trimmed gain resistors	Internal 60 kΩ metal-film resistors trimmed for <±0.1% gain error at G=100 - ensures stable gain across temperature without external calibration.
Input overvoltage protection	±40 V fault tolerance on both inputs - prevents damage during sensor hot-plug, ESD events, or power sequencing mismatches.
Low-power sleep mode	Reduces total supply current to ±1 µA while maintaining high-Z output - enables microamp-level average current in wake-sleep cycling.
Single-supply compatibility	Operates down to +2.7 V with rail-to-rail output swing referenced to IAREF - supports portable and energy-harvesting sensor nodes.

Applications

Pressure Transducer Interface	Temperature RTD Bridge Amplifier
Use Scenario: Amplifying mV-level differential output from a 350 Ω Wheatstone bridge pressure sensor powered by onboard 5 V reference. IC Role / Device Role / Timing Role: Provides precision differential gain (G=100), bridge excitation, and common-mode rejection in a single IC. Use Value: Eliminates need for separate reference IC and discrete op amp stages, reducing layout area by >40% and improving thermal tracking.	Use Scenario: Conditioning output of a 100 Ω Pt100 RTD in a 4-wire configuration with 2.5 V excitation and cold-junction compensation. IC Role / Device Role / Timing Role: Delivers low-drift gain, precise 2.5 V reference, and Sense pin for 4-wire Kelvin correction. Use Value: Achieves <0.1 °C measurement uncertainty over –40°C to +85°C without external trimming or calibration.
Battery-Powered Data Logger	Industrial Process Controller Input Module
Use Scenario: Signal conditioning for multi-channel analog inputs in a solar-powered environmental monitor operating 24/7 on Li-SOCl₂ cells. IC Role / Device Role / Timing Role: Performs low-noise amplification (38 nV/√Hz) and enters µA-level sleep between 10 s sampling intervals. Use Value: Extends battery life to >10 years by minimizing active current (460 µA) and enabling deterministic low-power duty cycling.	Use Scenario: Front-end amplification for 4–20 mA loop-powered field transmitters in PLC analog input cards requiring 100+ year MTBF. IC Role / Device Role / Timing Role: Provides robust 100 dB CMR, ±40 V input protection, and wide supply range (±15 V) for noisy plant-floor environments. Use Value: Reduces field failure rate by eliminating external protection components and ensuring stable performance under EMI and ground-shift conditions.

Pressure Transducer Interface

Temperature RTD Bridge Amplifier

Use Scenario: Amplifying mV-level differential output from a 350 Ω Wheatstone bridge pressure sensor powered by onboard 5 V reference.

IC Role / Device Role / Timing Role: Provides precision differential gain (G=100), bridge excitation, and common-mode rejection in a single IC.

Use Value: Eliminates need for separate reference IC and discrete op amp stages, reducing layout area by >40% and improving thermal tracking.

Use Scenario: Conditioning output of a 100 Ω Pt100 RTD in a 4-wire configuration with 2.5 V excitation and cold-junction compensation.

IC Role / Device Role / Timing Role: Delivers low-drift gain, precise 2.5 V reference, and Sense pin for 4-wire Kelvin correction.

Use Value: Achieves <0.1 °C measurement uncertainty over –40°C to +85°C without external trimming or calibration.

Battery-Powered Data Logger

Industrial Process Controller Input Module

Use Scenario: Signal conditioning for multi-channel analog inputs in a solar-powered environmental monitor operating 24/7 on Li-SOCl₂ cells.

IC Role / Device Role / Timing Role: Performs low-noise amplification (38 nV/√Hz) and enters µA-level sleep between 10 s sampling intervals.

Use Value: Extends battery life to >10 years by minimizing active current (460 µA) and enabling deterministic low-power duty cycling.

Use Scenario: Front-end amplification for 4–20 mA loop-powered field transmitters in PLC analog input cards requiring 100+ year MTBF.

IC Role / Device Role / Timing Role: Provides robust 100 dB CMR, ±40 V input protection, and wide supply range (±15 V) for noisy plant-floor environments.

Use Value: Reduces field failure rate by eliminating external protection components and ensuring stable performance under EMI and ground-shift conditions.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
AD8226ARMZ	No integrated reference; requires external 2.5 V reference IC; lower CMR (90 dB @ G=100); SO-8 package.	Suitable only where board space allows separate reference and where 100 dB CMR is not required.	Select when cost sensitivity outweighs integration benefit and reference voltage flexibility is not needed.
INA333AIDR	Includes internal reference (1.2 V), but fixed reference only; no 2.5 V/5 V/10 V selection; lower max gain (1000); SO-8 package.	Applicable for low-gain, low-voltage (1.8–5.5 V) portable designs where 10 V excitation is unnecessary.	Choose for ultra-low-power (17 µA) single-supply systems below 5.5 V where flexible reference voltage is secondary.

Compared with AD8226ARMZ and INA333AIDR, the INA125U/2K5 uniquely combines programmable reference voltage selection (1.24 V / 2.5 V / 5 V / 10 V), 100 dB CMR, and SO-16 layout compatibility - making it the only option supporting high-accuracy, multi-transducer bridge excitation in a single IC without external support components.

Availability

INA125U/2K5 is available at Aetrix Electronics and suitable for industrial process control, battery-powered sensor nodes, and factory automation systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for INA125U/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 acquired Burr-Brown in 2000 and maintains full production, qualification, and technical support for legacy precision analog products including the INA125 series.

The INA125 product line was engineered specifically for high-accuracy sensor signal conditioning in harsh industrial environments - integrating precision amplification, reference generation, and robust input protection into one monolithic solution.

FAQ

What is the maximum gain achievable with INA125U/2K5, and how is it set?

The INA125U/2K5 supports a maximum gain of 10,000 V/V, achieved by connecting a 6.04 Ω resistor between pins 7 (RG) and 8 (RG). Gain is calculated using the formula G = 4 + 60 kΩ/RG, where the internal 60 kΩ resistor is laser-trimmed for accuracy. For G = 10,000, the INA125U/2K5 requires careful PCB layout to minimize parasitic resistance, as wiring and contact resistance become significant at such low RG values.

Can INA125U/2K5 operate from a single +3.3 V supply, and what reference voltage is supported?

Yes, the INA125U/2K5 operates from a single +3.3 V supply, but only the 1.24 V bandgap reference (VREFBG) is usable due to the minimum 1.25 V headroom requirement. Connecting VREFOUT to pin 13 (VREFBG) provides a stable 1.24 V ±0.5% output. The 2.5 V, 5 V, and 10 V references require higher supply voltages (+3.75 V, +6.25 V, and +11.25 V respectively) and are not functional at +3.3 V.

How does the Sense pin (pin 16) improve measurement accuracy in bridge applications?

The Sense pin (pin 16) on the INA125U/2K5 enables true 4-wire (Kelvin) sensing by connecting directly to the bridge's output midpoint, bypassing voltage drop in excitation traces. This eliminates errors caused by trace resistance and ensures the amplifier measures only the actual bridge differential voltage. When used with the INA125U/2K5's integrated reference, it delivers <0.01% linearity in precision load cell interfaces.

What is the wake-up time from sleep mode, and how does it affect settling accuracy?

The INA125U/2K5 achieves full operational stability within 150 µs after SLEEP pin rises above 2.7 V. During wake-up, input offset voltage changes by less than ±100 µV (per typical curve), ensuring rapid reacquisition of baseline accuracy. For applications requiring <0.001% gain stability, allow ≥500 µs delay before sampling - a value confirmed by the "Input-Referred Offset Voltage vs Sleep Turn-On Time" plot in the INA125U/2K5 datasheet.

Is external decoupling required for stable operation of INA125U/2K5, and where should capacitors be placed?

Yes, the INA125U/2K5 requires local 0.1 µF ceramic decoupling capacitors: one between V+ (pin 1) and V− (pin 3), and another between VREFCOM (pin 14) and ground. These must be placed within 2 mm of their respective pins to suppress high-frequency noise and prevent oscillation. The datasheet explicitly states that noisy or high-impedance supplies necessitate these capacitors - omission risks degraded CMR and reference instability in the INA125U/2K5.

INA125U/2K5 Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: -

Package/Case:: 16-SOIC (0.154", 3.90mm Width)

Packaging:: Tape & Reel (TR)

Product Status:: Active

Amplifier Type:: Instrumentation

Number of Circuits:: 1

Output Type:: -

Slew Rate:: 0.2V/µs

Gain Bandwidth Product:: -

-3db Bandwidth:: 150 kHz

Current - Input Bias:: 10 nA

Voltage - Input Offset:: 50 µV

Current - Supply:: 460µA

Current - Output / Channel:: 12 mA

Voltage - Supply Span (Min):: 2.7 V

Voltage - Supply Span (Max):: 36 V

Operating Temperature:: -40°C ~ 85°C

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 16-SOIC

INA125U/2K5 FAQ

1.How can I place an order for INA125U/2K5 through Aetrix?

Please submit a Request for Quotation (RFQ) for INA125U/2K5 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for INA125U/2K5 reliable?

The price and inventory of INA125U/2K5 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for INA125U/2K5 is usually 5 days.

3.What payment methods are accepted for INA125U/2K5?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for INA125U/2K5 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for INA125U/2K5?

INA125U/2K5 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your INA125U/2K5 order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for INA125U/2K5?

For technical support, including INA125U/2K5 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your INA125U/2K5 requirements.

6.How does Aetrix verify that INA125U/2K5 is sourced from the original manufacturer or authorized distributors?

All INA125U/2K5 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that INA125U/2K5 meets industry standards.

7.What is the process for return or replacement of INA125U/2K5?

All INA125U/2K5 units undergo pre-shipment inspection (PSI). If there is an issue with INA125U/2K5, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The INA125U/2K5 part is unused and in its original packaging.

Return procedure for INA125U/2K5:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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