Texas Instruments INA122PAG4

Overview

INA122PAG4 from Texas Instruments is a precision single-supply micropower instrumentation amplifier optimized for low-noise differential signal acquisition in portable and battery-powered systems. It delivers 60μA quiescent current, rail-to-rail output swing, 250μV max offset voltage, and gain programmable from 5V/V to 10,000V/V via external resistor RG - enabling high-accuracy sensor interfacing in ECG monitors and pressure transmitters.

For engineers reviewing the INA122PAG4 datasheet, INA122PAG4 pinout, INA122PAG4 application, or INA122PAG4 equivalent, key selection considerations include its 2.2V–36V supply range, −40°C to +85°C operating temperature, SOIC-8 package, and verified performance in low-power medical and industrial sensing circuits with <3μV/°C offset drift and 60nV/√Hz input-referred noise.

Technical Context

The INA122PAG4 implements a two-op-amp architecture with internal laser-trimmed 100kΩ/25kΩ resistor networks, enabling precise gain setting (G = 5 + 200kΩ/RG) and excellent common-mode rejection (96dB typ). Its input stage incorporates precision level-shifting buffers to extend common-mode range to ground on single supplies - a critical feature distinguishing it from generic op-amp-based instrumentation topologies.

Unlike conventional three-op-amp amplifiers, the INA122PAG4 achieves micropower operation without sacrificing rail-to-rail output swing or input bias current performance (25nA max). The RG pins (1 and 8) are internally biased at shifted potentials due to level-shifting, meaning external gain resistors connect to non-input nodes - a design detail essential for accurate gain calibration and overload analysis.

Key Specifications

Pinout & Package

INA122PAG4 is supplied in an 8-pin SOIC package (4.9mm × 6mm), rated for −40°C to +85°C operation. This surface-mount package supports automated assembly and provides thermal resistance R_θJA = 129.2°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD623ARZ and INA333AIDR, the INA122PAG4 offers the best balance of micropower operation, proven field reliability in medical devices, and straightforward gain programming - making it ideal for cost-sensitive, battery-constrained instrumentation where 100kHz bandwidth suffices.

Availability

INA122PAG4 is available at Aetrix Electronics and suitable for portable electronics, field transmitters and sensors, and electrocardiogram (ECG) systems requiring stable component supply across extended production lifecycles.

Supply support for INA122PAG4 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 is a global semiconductor leader specializing in analog and embedded processing technologies, with decades of expertise in precision signal chain solutions.

The INA122 product line was engineered specifically for low-power, high-accuracy sensor signal conditioning in portable and industrial instrumentation - emphasizing micropower operation, rail-to-rail output, and robust single-supply functionality.

FAQ

What is the maximum gain achievable with INA122PAG4, and how is it set?

The INA122PAG4 supports a maximum gain of 10,000V/V, set by connecting an external resistor (RG) between pins 1 and 8. The gain equation is G = 5 + 200kΩ/RG; for 10,000V/V, RG = 20Ω. This configuration is validated in TI's SBOS069B datasheet and maintains specified accuracy and drift performance across the −40°C to +85°C range. The INA122PAG4's laser-trimmed internal resistors ensure consistent gain behavior regardless of supply voltage within 2.2V–36V.

Does INA122PAG4 support true single-supply operation down to 2.2V?

Yes, the INA122PAG4 is explicitly designed for true single-supply operation from 2.2V to 36V. Its input stage uses precision level-shifting buffers that extend the common-mode input range to ground, enabling linear operation even when both inputs and REF are tied to 0V. This eliminates the need for negative supplies or charge pumps in portable applications - a capability confirmed in Section 6.1 and Figure 6-2 of the official datasheet for INA122PAG4.

What is the purpose of the REF pin on INA122PAG4, and how should it be used?

On the INA122PAG4, the REF pin (pin 5) sets the output voltage offset reference. It must be driven by a low-impedance source (<10Ω) to preserve common-mode rejection ratio (CMRR); a 10Ω series resistor degrades CMRR to ~80dB. In most applications, REF is grounded. For offset trimming, a buffered voltage source (e.g., OPA391 driving REF) can adjust output DC level without compromising CMRR - as demonstrated in Figure 7-1 of the INA122PAG4 datasheet.

Can INA122PAG4 drive capacitive loads, and what is its stability limit?

The INA122PAG4 is stable with capacitive loads up to 1000pF, as specified in Section 5.5 of its datasheet. Exceeding this value may cause peaking or oscillation due to phase margin degradation. For larger loads (e.g., ADC input capacitance + PCB trace), isolation with a small series resistor (10–50Ω) and/or local decoupling is recommended. This stability limit applies across the full 5V/V–10,000V/V gain range and all supply voltages supported by INA122PAG4.

How does the input protection scheme work on INA122PAG4?

The INA122PAG4 integrates internal ESD diodes from each input (pins 2 and 3) to the supply rails (+VS and −VS). These diodes clamp transient overvoltages but require external current limiting if input signals exceed the rails by more than 0.3V - a series resistor must restrict current to <5mA. This protection architecture is documented in Section 6.3.3 and Absolute Maximum Ratings (Section 5.1) of the INA122PAG4 datasheet, ensuring robustness in industrial sensor environments.