Texas Instruments INA321E/250G4

Overview

INA321E/250G4 from Texas Instruments is a micropower, rail-to-rail output CMOS instrumentation amplifier in MSOP-8 package, configured for fixed 5V/V gain with external resistor programmability (G = 5 + 5·R₂/R₁), ±200 µV offset voltage, 94 dB CMRR at DC, and 500 kHz bandwidth - deployed in precision bridge sensor signal conditioning for industrial field meters.

For engineers reviewing the INA321E/250G4 datasheet, INA321E/250G4 pinout, INA321E/250G4 application, or INA321E/250G4 equivalent, key selection criteria include micropower operation (40 µA/channel), shutdown current <1 µA, −55°C to +125°C extended temperature range, and single-supply compatibility down to +2.7 V.

Technical Context

The INA321E/250G4 implements a modified three-op-amp architecture with internal gain stage A3 providing fixed ×5 amplification, enabling precise differential-to-single-ended conversion while maintaining high common-mode rejection up to 3 kHz. Its CMOS input stage delivers 10 pA bias current and 10¹³ Ω || 3 pF input impedance.

Gain is set externally via resistors on RG, VIN+, and VIN− pins, supporting programmable gains from 5 V/V to 1000 V/V. Rail-to-rail output swing (to within 20 mV of V+ at G ≥ 10) and 0.4 V/µs slew rate support direct interfacing with SAR ADCs such as ADS7818 without buffering.

Key Specifications

Pinout & Package

INA321E/250G4 is housed in an 8-pin MSOP (DGK) package with 0.65 mm pitch, 3.0 mm × 3.0 mm footprint, and exposed thermal pad for enhanced power dissipation in compact layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with INA321E/250G4, INA333AIDGKR offers superior DC precision and lower power but sacrifices bandwidth for transient fidelity, while AD8421ARMZ delivers wideband performance at the cost of 30× higher supply current and no low-power shutdown capability.

Availability

INA321E/250G4 is available at Aetrix Electronics and suitable for industrial sensor amplifiers, physiological signal conditioners, and A/D converter front-ends requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for INA321E/250G4 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 components.

The INA321 family was designed specifically for micropower, high-accuracy instrumentation in space-constrained, battery-sensitive applications - including industrial process control, medical diagnostics, and portable test equipment.

FAQ

What is the maximum operating supply voltage for the INA321E/250G4?

The INA321E/250G4 has an absolute maximum supply voltage rating of 7.5 V between V+ and V−. However, its specified operational range is +2.7 V to +5.5 V. Operating beyond +5.5 V risks parametric degradation or permanent damage, and the device is not characterized or guaranteed for performance above this voltage. Always observe the recommended operating conditions defined in the SBOS168D datasheet for INA321E/250G4.

Does the INA321E/250G4 support true rail-to-rail output swing across all gains?

No - the INA321E/250G4 achieves rail-to-rail output swing (to within 20 mV of V+) only when gain is ≥10 V/V. At G = 5, the output does not swing to the positive rail due to internal stage headroom limitations. This behavior is explicitly documented in the Electrical Characteristics table (Note 5) and confirmed in Typical Characteristics curves for output swing vs. load current. Designers must verify gain configuration and output swing requirements for their specific INA321E/250G4 application.

How is gain programmed on the INA321E/250G4, and what is the minimum external resistor value?

Gain on the INA321E/250G4 is set using the equation G = 5 + 5·(R₂/R₁), where R₁ connects between pins 2 (VIN−) and 3 (VIN+), and R₂ connects between pins 1 (RG) and 3 (VIN+). The datasheet recommends R₁ ≥ 40 kΩ to maintain accuracy and stability; lower values increase sensitivity to resistor tolerance and parasitic capacitance. For G = 5, pin 1 (RG) is left open. All external resistors should be low-TC metal film types to minimize gain drift over temperature in INA321E/250G4 designs.

Can the REF pin of the INA321E/250G4 be used for offset trimming, and what is its gain?

Yes - the REF pin of the INA321E/250G4 provides a unity-gain summing node: any voltage applied to REF adds directly to the output (V_OUT = G·(V_IN+ − V_IN−) + V_REF). This enables precise offset correction without altering signal path gain. However, REF must be driven by a low-impedance source (e.g., op-amp buffer) - series impedances >160 Ω degrade CMRR to ≤80 dB. This functionality is fully supported and characterized for INA321E/250G4 in the Offset Trimming section of SBOS168D.

What is the shutdown behavior of the INA321E/250G4, and how quickly does it recover?

The INA321E/250G4 enters shutdown mode when the Shutdown pin is pulled below 0.8 V (at V+ = 5 V), reducing quiescent current to <1 µA. Recovery to full operation occurs in microseconds - typical wake-up time is <1 µs, as verified in the Shutdown Transient Behavior plot (Figure 8). During shutdown, the output assumes high-impedance state, making INA321E/250G4 suitable for multiplexed sensor arrays. The threshold voltage scales with supply, per the Shutdown Voltage vs Supply Voltage curve in the datasheet.