Texas Instruments INA122P

Overview

INA122P from Texas Instruments is a precision two-op-amp instrumentation amplifier optimized for low-power, single-supply sensor signal conditioning. It delivers 60μA quiescent current, rail-to-rail output swing, and 250μV max offset voltage over −40°C to +85°C - enabling high-accuracy differential measurement in battery-powered ECGs and pressure transmitters.

For engineers reviewing the INA122P datasheet, INA122P pinout, INA122P application, or INA122P equivalent, key selection factors include its 2.2V–36V supply range, external gain-setting resistor (RG) configuration, laser-trimmed offset drift of 3μV/°C, and SOIC/PDIP package compatibility with portable medical and industrial sensing designs.

Technical Context

The INA122P implements a monolithic two-op-amp architecture with internal level-shifting buffers that extend input common-mode range to ground on single supplies. Its gain is set by a single external resistor (RG) between pins 1 and 8, supporting 5V/V to 10000V/V via G = 5 + 200kΩ/RG.

Internal laser-trimmed metal-film resistors ensure ±0.1% max gain error at G=5 and ±0.5% at G=100, while input bias current remains ≤25nA and CMRR reaches 96dB (typical) across 0–3.4V common-mode range - critical for rejecting noise in bridge-based sensor interfaces.

Key Specifications

Pinout & Package

INA122P is supplied in an 8-pin PDIP package (9.81mm × 9.43mm), rated for −40°C to +85°C operation. Pin functions are validated per TI SBOS069B datasheet Figure 4-1 and Table 4-1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with INA326EA and AD8221ARMZ, the INA122P uniquely balances micropower operation (60μA), true 2.2V single-supply start-up, and PDIP/SOIC flexibility - making it irreplaceable in cost-sensitive, long-life portable medical and industrial sensor nodes where supply headroom and layout reliability are constrained.

Availability

INA122P is available at Aetrix Electronics and suitable for portable electronics, field transmitters and sensors, and electrocardiograms (ECGs) requiring stable component supply across extended product lifecycles.

Supply support for INA122P 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 INA122P belongs to TI's precision instrumentation amplifier product line, engineered specifically for low-power, high-accuracy sensor signal conditioning in portable and industrial measurement systems.

FAQ

What is the minimum supply voltage required for reliable operation of the INA122P?

The INA122P operates reliably down to 2.2V on a single supply (or ±1.1V dual supply), verified across the full −40°C to +85°C temperature range. At 2.2V, output swing remains rail-to-rail with reduced load drive capability; design margin increases significantly above 3V. This makes the INA122P suitable for coin-cell and energy-harvesting applications where other instrumentation amplifiers fail to start.

How does the INA122P achieve rail-to-rail output with single-supply operation?

The INA122P uses internal precision level-shifting buffers on both inputs and the A2 op-amp output stage to shift operating points, enabling valid linear output swing from within 100mV of V– (ground) to within 50mV of V+ across its full supply range. This eliminates the need for negative supplies in sensor interfaces while preserving common-mode rejection - a key differentiator versus discrete two-op-amp implementations.

Can the INA122P be used with a grounded reference (REF = 0V) in single-supply configurations?

Yes - the INA122P is explicitly designed for REF = 0V operation in single-supply mode. The datasheet specifies performance under this condition, including CMRR, offset, and bandwidth. However, the REF pin must be driven by a low-impedance source (<10Ω); placing a 0Ω resistor or direct PCB trace to ground meets this requirement and preserves >80dB CMRR.

What is the maximum gain achievable with the INA122P, and how is it set?

The INA122P supports gains from 5V/V to 10,000V/V using a single external resistor (RG) connected between pins 1 and 8, per the equation G = 5 + 200kΩ/RG. For G = 10,000V/V, RG = 20Ω (standard 1% value). Gain accuracy is ±0.1% at G=5 and ±0.5% at G=100, with drift dominated by RG's temperature coefficient - select RG with ≤25ppm/°C TC for best stability.

Does the INA122P require input bias current return paths, and why?

Yes - the INA122P has input bias current up to −25nA (flowing out of pins 2 and 3), requiring explicit return paths to maintain linear operation. Without them, inputs float beyond common-mode range, causing saturation. For balanced performance, use equal resistors from each input to REF or ground; for low-source-impedance bridges, a single path to REF suffices - confirmed in TI's Figure 7-2 and Section 7.1.2.