Texas Instruments INA125PAG4

Overview

INA125PAG4 from Texas Instruments (formerly 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 minimum 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 without external components.

For engineers reviewing the INA125PAG4 datasheet, INA125PAG4 pinout, INA125PAG4 application, or INA125PAG4 equivalent, key selection criteria include its single-resistor programmable gain (G = 4 to 10,000), ±40 V input protection, sleep-mode quiescent current ≤25 µA, and operation on single +2.7 V to +36 V or dual ±1.35 V to ±18 V supplies.

Technical Context

The INA125PAG4 integrates two high-precision op amps (A1 and A2) in a classic three-op-amp instrumentation topology, with laser-trimmed internal 30 kΩ/10 kΩ resistor networks defining gain accuracy and drift. Its reference section uses a bandgap core with ratio-trimmed resistive dividers to generate stable 2.5 V, 5 V, or 10 V outputs - each accurate to ±0.5% max with ±35 ppm/°C drift.

Sleep mode is controlled by a dedicated logic-level SLEEP pin (pin 3), which reduces total supply current to ±1 µA when pulled ≤100 mV relative to VREFCOM. Wake-up time is 150 µs, and output impedance rises to ~80 kΩ during shutdown - preserving system integrity during duty-cycled operation.

Key Specifications

Pinout & Package

INA125PAG4 is housed in a 16-pin plastic DIP (PDIP-N) package with 0.300-inch body width and through-hole mounting. Thermal resistance θJA is 80°C/W. Pin 1 is located at the left end of the top row when viewed from above with notch or dot oriented upward.

Key Features

Applications

Equivalent & Alternatives

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

Compared with INA125PAG4, INA126PA trades integrated reference and DIP packaging for lower power and smaller size, while AD8226ARZ offers lower unit cost and simplified layout at the expense of excitation capability and sleep control - making INA125PAG4 uniquely suited for self-contained bridge measurement in industrial DIP-based systems.

Availability

INA125PAG4 is available at Aetrix Electronics and suitable for pressure transducer signal conditioning, battery-powered data loggers, and factory automation analog input modules requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for INA125PAG4 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, emphasizing high-accuracy signal chain solutions for industrial, medical, and test equipment markets.

The INA125 product line was developed specifically for integrated bridge sensor signal conditioning - combining instrumentation amplification, precision excitation, and low-power operation in a single IC to simplify front-end design for strain gauges, load cells, and RTDs.

FAQ

What is the maximum gain achievable with the INA125PAG4, and how is it set?

The INA125PAG4 supports gains from 4 to 10,000 V/V, set by a single external resistor RG connected between pins 8 and 9 per the equation G = 4 + 60 kΩ/RG. For G = 10,000, RG = 6 Ω (e.g., 6.04 Ω 1% metal film). At this gain, wiring resistance becomes critical - use Kelvin connections and avoid sockets to prevent unstable gain error. The INA125PAG4's laser-trimmed internal resistors ensure gain accuracy remains within ±1% even at G = 1000.

Can the INA125PAG4 operate from a single 3.3 V supply, and what limitations apply?

Yes, the INA125PAG4 operates from +2.7 V to +36 V single supply. At +3.3 V, only the 1.24 V bandgap reference (VREFBG) is usable, since V+ must exceed VREF by ≥1.25 V. Input common-mode range shrinks to approximately +1.1 V to +3.6 V, and output swing is limited to ~0.3 V above ground and ~0.15 V below V+. For reliable operation, bias VIN+ and VIN− at V+/2 using matched resistors, and route IAREF and VREFCOM directly to ground with low-inductance traces. The INA125PAG4 maintains 78 dB CMR at G = 4 under these conditions.

How does the sleep mode of the INA125PAG4 affect output behavior and wake-up performance?

When the SLEEP pin (pin 3) is pulled ≤100 mV relative to VREFCOM, the INA125PAG4 shuts down both amplifier and reference sections, reducing total supply current to ±1 µA and raising output impedance to ~80 kΩ. Output voltage becomes undefined during sleep. Upon wake-up (SLEEP ≥ 2.7 V), the INA125PAG4 achieves full accuracy within 150 µs - verified by "Input-Referred Offset Voltage vs Sleep Turn-On Time" curves. Residual offset shift is <10 µV, ensuring minimal settling error in precision acquisition. No external reset is needed for the INA125PAG4.

What is the purpose of the Sense pin (pin 11) on the INA125PAG4, and should it be connected externally?

The Sense pin (pin 11) on the INA125PAG4 is an internal current-sense node used by the reference regulator to monitor load current - it is not intended for external connection. Leaving pin 11 unconnected has no effect on operation or accuracy. External connection could disrupt reference regulation or introduce noise. All reference current flows out of VREFCOM (pin 16), which must be tied to a low-impedance ground point to prevent ground-loop errors. The INA125PAG4 datasheet explicitly states "no external connection required" for pin 11.

Does the INA125PAG4 require external capacitors for stability, and what values are recommended?

Yes, the INA125PAG4 requires local decoupling: 0.1 µF ceramic capacitors between V+ (pin 1) and V− (pin 3), and between VREFOUT (pin 4) and VREFCOM (pin 16). These suppress high-frequency noise and prevent oscillation, especially when driving capacitive loads >100 pF. For VREFOUT, a 0.01 µF to 0.1 µF capacitor improves transient response - larger values (>1 µF) may cause instability. No compensation network is needed on the amplifier output; the INA125PAG4 is unity-gain stable. Layout best practice is to place all capacitors within 5 mm of their respective pins.