Texas Instruments INA321E/250

Overview

INA321E/250 from Texas Instruments is a single-channel, rail-to-rail output, micropower CMOS instrumentation amplifier in MSOP-8 package. It delivers 5 V/V fixed gain (user-programmable to 5–1000 V/V), ±200 µV max input offset voltage, 94 dB CMRR at DC, 500 kHz bandwidth, and operates from +2.7 V to +5.5 V supply across −55°C to +125°C - ideal for precision bridge sensor signal conditioning in battery-powered industrial monitoring systems.

For engineers reviewing the INA321E/250 datasheet, INA321E/250 pinout, INA321E/250 application, or INA321E/250 equivalent, key selection considerations include micropower operation (40 µA/channel), shutdown current <1 µA, rail-to-rail output swing within 20 mV of rails (G ≥ 10), 10 pA input bias current, and external gain resistor flexibility for system-level calibration.

Technical Context

The INA321E/250 implements a three-op-amp instrumentation architecture with an internal 5× gain stage and user-configurable external resistors (G = 5 + 5·R₂/R₁). Its CMOS input stage enables ultra-low bias current (10 pA) and high input impedance (10¹³ Ω || 3 pF), supporting high-impedance sensors without loading error.

It features a dedicated shutdown pin enabling microsecond wake-up from sub-1 µA quiescent state, and a reference pin that sets output zero level while directly influencing common-mode input range - requiring low-impedance drive to maintain >90 dB CMRR. Output buffer supports 25 kΩ+ loads with rail-to-rail swing down to (V+) − 20 mV at G ≥ 10.

Key Specifications

Pinout & Package

INA321E/250 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 INA333AIDGKR and AD8221ARMZ, the INA321E/250 uniquely balances micropower operation (40 µA), extended temperature qualification (−55°C to +125°C), and programmable gain in a space-constrained MSOP-8 - making it optimal for cost-sensitive, wide-temp industrial sensor nodes where power and reliability are co-primary constraints.

Availability

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

Supply support for INA321E/250 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 low-power, high-accuracy instrumentation in resource-constrained environments - targeting industrial process control, medical diagnostics, and energy metering applications demanding rail-to-rail operation and robust noise rejection.

FAQ

What is the maximum gain achievable with INA321E/250 using external resistors?

The INA321E/250 supports externally programmable gain from 5 V/V to 1000 V/V via the equation G = 5 + 5·(R₂/R₁). At G = 1000, R₂/R₁ = 199, requiring precision-matched resistors with low TCR to maintain gain accuracy and minimize drift. The device maintains ≥75 dB CMRR up to 3 kHz even at high gains, ensuring noise rejection remains effective in real-world conditions. Gain error is specified at ±0.1% max over temperature for the entire range.

Does INA321E/250 require external decoupling capacitors, and where should they be placed?

Yes, the INA321E/250 requires 0.1 µF ceramic decoupling capacitors placed as close as possible to both V+ (Pin 6) and V− (Pin 4) pins to suppress high-frequency noise and ensure stability. These capacitors must connect directly to the power planes with minimal trace length - TI's SBOS168D datasheet specifies this as mandatory for reliable operation in noisy industrial or mixed-signal environments. Failure to implement local decoupling may cause oscillation or degraded PSRR performance.

Can INA321E/250 drive a 600 Ω load directly, or is an external buffer required?

The INA321E/250 is not rated to drive 600 Ω loads directly; its output stage is optimized for ≥10 kΩ loads. Driving lower impedances causes significant output swing loss and increased distortion. For 600 Ω applications, TI recommends cascading with the OPA340 (as shown in Figure 4 of SBOS168D), which provides rail-to-rail swing and 60 mA output current. This two-stage configuration preserves INA321E/250's precision while extending drive capability - critical for audio or actuator interface circuits.

How does the REF pin affect common-mode input range in INA321E/250?

The REF pin directly sets the output zero level and constrains the input common-mode voltage range per V_CM(max) = V₊ − 1.2 V and V_CM(min) ≈ (5/4)V_CM − (1/4)V_REF. If REF is set too high (e.g., >V₊ − 1.2 V), the upper input limit collapses, causing clipping. TI's typical curves show optimal REF at ~V₊/2 for symmetric swing. Deviations require recalculating allowable V_CM using the equations in Section 11 of SBOS168D to avoid saturation.

Is INA321E/250 RoHS-compliant and lead-free?

Yes, INA321E/250 is RoHS-compliant and lead-free, as confirmed in TI's Package Option Addendum (11-Nov-2025). It carries "Yes" for RoHS status and uses NiPdAu (nickel-palladium-gold) or NIPDAU (nickel-palladium-gold) lead finish per TI's material declaration. The MSOP-8 (DGK) package has MSL Level-2 rating (260°C peak reflow, 1-year floor life), requiring standard SMT handling protocols. Full compliance documentation is available via TI's Quality & Environmental page.