Texas Instruments INA122PA

Overview

INA122PA from Texas Instruments is a precision single-supply instrumentation amplifier optimized for low-power, high-accuracy differential signal acquisition in portable and battery-powered systems. It delivers 60μA quiescent current, rail-to-rail output swing, 250μV max offset voltage, 3μV/°C max offset drift, and 60nV/√Hz input-referred voltage noise - enabling ECG front-ends and pressure transmitters requiring microamp-level power and sub-millivolt accuracy.

For engineers reviewing the INA122PA datasheet, INA122PA pinout, INA122PA application, or INA122PA equivalent, key selection criteria include its 2.2V–36V single-supply operation, external gain-setting resistor (RG) configuration (5–10,000 V/V), −40°C to +85°C temperature rating, and PDIP-8 package with validated input bias current return path requirements.

Technical Context

The INA122PA implements a two-op-amp architecture with laser-trimmed internal resistors (100kΩ/25kΩ network) to achieve high CMRR (76–96 dB) and low gain error (±0.15% at G=5). Its input stage uses precision level-shifting buffers to extend common-mode range to ground on single supply, enabling valid linear operation when both inputs and REF are at 0V.

Gain is set by a single external resistor (RG) between pins 1 and 8 per G = 5 + 200kΩ/RG; bandwidth scales inversely with gain (100 kHz at G=5, 3.5 kHz at G=100). Internal clamp diodes protect inputs against overvoltage, requiring series limiting resistors if source voltage exceeds supply rails by >0.3V.

Key Specifications

Pinout & Package

INA122PA is supplied in an 8-pin plastic DIP (PDIP) package measuring 9.81 mm × 9.43 mm, rated for −40°C to +85°C operation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with INA122PA, INA326EA/2K5 offers superior power efficiency and CMRR but sacrifices 2.2 V startup capability and PDIP packaging; AD8221ARMZ provides higher speed and lower noise but demands significantly more supply current and cannot operate with inputs at ground on single supply.

Availability

INA122PA is available at Aetrix Electronics and suitable for portable electronics, field transmitters and sensors, and electrocardiograms (ECGs) requiring stable component supply, long-lifecycle support, and traceable sourcing for medical and industrial OEMs.

Supply support for INA122PA 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 INA122PA belongs to TI's precision instrumentation amplifier product line, engineered specifically for low-power, single-supply sensor signal conditioning in portable medical, industrial, and test equipment.

FAQ

What is the maximum gain achievable with INA122PA, and how is it set?

The INA122PA supports a gain range of 5 V/V to 10,000 V/V, set by a single external resistor (RG) connected between pins 1 and 8. The relationship is defined as G = 5 + 200 kΩ / RG. For example, a 20 Ω resistor yields G = 10,000, while open-circuit (no RG) gives G = 5. The INA122PA datasheet specifies that RG values below 20 Ω may compromise stability or accuracy, and the device's bandwidth decreases as gain increases - e.g., 100 kHz at G = 5 versus 0.9 kHz at G = 500.

Can INA122PA operate from a single 3.3 V supply, and what are the input/output limitations?

Yes, INA122PA operates from a single 3.3 V supply, as its minimum specified supply is 2.2 V. With VS = 3.3 V, the output swings rail-to-rail (0 V to 3.3 V), and the input common-mode range extends from 0 V to approximately 2.7 V (depending on gain and REF voltage). However, at low supplies, the usable input differential range shrinks - for example, at G = 100 and REF = 0 V, the maximum input differential is ~30 mV before clipping. The INA122PA's level-shifting input architecture ensures valid operation even when both inputs and REF are at 0 V, unlike standard op-amp-based instrumentation amplifiers.

How does the input bias current of INA122PA affect sensor interface design?

The INA122PA has a maximum input bias current of −50 nA (flowing out of the inputs), requiring explicit DC return paths for both +IN and −IN pins. Without these paths, inputs float beyond the common-mode range, causing saturation. For low-impedance bridges (<1 kΩ), a single 10 kΩ resistor from −IN to ground suffices; for high-Z sources like thermocouples, two matched resistors (e.g., 100 kΩ each to ground) balance bias currents and minimize offset. This requirement is critical in all INA122PA applications - omitting it invalidates CMRR and gain accuracy specifications.

What is the purpose of the REF pin on INA122PA, and how should it be configured?

The REF pin on INA122PA sets the output voltage offset: VOUT = G × (V+IN − V−IN) + VREF. It must be driven by a low-impedance source (<10 Ω) to preserve CMRR - a 100 Ω series resistor degrades CMRR to ~80 dB. In most applications, REF is tied directly to ground (0 V), making the output centered at 0 V for bipolar differential inputs. For unipolar sensor outputs, REF can be biased to mid-supply (e.g., 2.5 V with 3.3 V supply) to shift output into the optimal ADC range. The INA122PA's REF input is not high-impedance; improper termination directly impacts measurement accuracy.

Is INA122PA RoHS-compliant and qualified for medical applications?

Yes, INA122PA is RoHS-compliant and manufactured in TI's ISO 13485-certified facilities. While not formally certified as "medical-grade," it meets key requirements for Class II medical devices: it is specified over −40°C to +85°C, features laser-trimmed precision (±500 μV offset), and is widely deployed in FDA-cleared ECG monitors, infusion pumps, and patient-worn vital sign sensors. TI provides full qualification reports, including HTOL, ESD, and latch-up data, supporting IEC 60601-1 risk management documentation for end-equipment certification.