Analog Devices Inc. AD8421BRMZ

Overview

AD8421BRMZ from Analog Devices is a low-power, ultralow-noise instrumentation amplifier with 3.2 nV/√Hz input voltage noise, 2.3 mA supply current, and 10 MHz bandwidth at G = 1. It serves as a precision front-end signal conditioner for high-impedance sensors in medical instrumentation and vibration analysis systems.

For engineers reviewing the AD8421BRMZ datasheet, AD8421BRMZ pinout, AD8421BRMZ application, or AD8421BRMZ equivalent, key selection criteria include input bias current (≤0.5 nA), CMRR (≥94 dB at DC, ≥80 dB at 20 kHz), gain flexibility (1–10,000 via single resistor), and robust ±40 V input overvoltage protection relative to supplies.

Technical Context

The AD8421BRMZ uses a current-feedback architecture that maintains 2 MHz bandwidth and 0.8 µs settling time to 0.001% at G = 100, enabling high-channel-count multiplexed data acquisition. Its input stage features 30 GΩ||3 pF impedance and patented protection allowing ±40 V input voltage beyond supply rails without damage.

Gain is set by a single external resistor across RG pins (G = 1 + 9.9 kΩ/RG); the REF pin supports precise output offset adjustment. Input common-mode range extends to −VS + 2.3 V and +VS − 1.8 V at 25°C, supporting wide-supply operation from ±2.5 V to ±18 V (or 5 V–36 V single supply).

Key Specifications

Pinout & Package

AD8421BRMZ is housed in an 8-lead MSOP package (3 mm × 3 mm, 0.65 mm pitch) with exposed pad thermally connected to −VS or left floating per layout guidelines.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD8420ARMZ and INA128UA, AD8421BRMZ delivers superior noise-performance trade-off (3.2 nV/√Hz at 2.3 mA), wider bandwidth at high gain, and stronger input protection-making it optimal for demanding medical and precision test equipment where signal integrity is non-negotiable.

Availability

AD8421BRMZ is available at Aetrix Electronics and suitable for medical instrumentation, precision data acquisition, and vibration analysis requiring stable component supply across extended temperature ranges (−40°C to +85°C).

Supply support for AD8421BRMZ 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

Analog Devices is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Norwood, MA.

The AD8421 product line targets precision signal conditioning in noise-sensitive measurement systems, emphasizing ultralow noise, low power, and robust input protection for medical, industrial, and test equipment applications.

FAQ

What is the maximum gain achievable with AD8421BRMZ?

The AD8421BRMZ supports a gain range of 1 to 10,000, set by a single external resistor across its RG pins using the formula G = 1 + 9.9 kΩ/RG. At G = 10,000, the required RG is 0.99 Ω, and performance specifications such as bandwidth (0.2 MHz) and settling time (6 µs to 0.001%) are guaranteed per the datasheet. The AD8421BRMZ maintains specified accuracy across this full range when using precision resistors with appropriate tolerance and TCR.

Does AD8421BRMZ require external components for basic operation?

Yes, AD8421BRMZ requires at minimum one external resistor across its RG pins to set gain, and decoupling capacitors (typically 0.1 µF ceramic + 10 µF tantalum per supply rail) for stable operation. The REF pin may be tied to ground or a reference voltage depending on output level-shifting needs. No external compensation or feedback networks are needed-the AD8421BRMZ is fully internally compensated and operates unconditionally stable across its entire gain range.

What is the operating temperature range for AD8421BRMZ?

The AD8421BRMZ is specified for full performance from −40°C to +85°C and operates reliably from −40°C to +125°C. This extended operational range is validated across all grades (AR, BR, ARM, BRM, ACP) and supports deployment in industrial control cabinets and automotive under-hood environments where ambient temperatures exceed standard commercial limits. Thermal resistance (θJA) for the MSOP package is 138.6°C/W, requiring modest PCB copper area for thermal management.

Can AD8421BRMZ be used with single-supply operation?

Yes, AD8421BRMZ supports single-supply operation from 5 V to 36 V. When operated from a single 5 V rail, the input common-mode range is −0.2 V to +3.2 V and output swing reaches within 1.6 V of each rail (i.e., ~0.8 V to ~4.2 V with RL = 2 kΩ). For optimal dynamic range, the REF pin should be biased to mid-supply (e.g., 2.5 V) to center the output. The AD8421BRMZ's rail-swing capability and input protection make it suitable for single-supply portable instrumentation without level-shifting circuitry.

How does the input overvoltage protection work on AD8421BRMZ?

The AD8421BRMZ incorporates proprietary input protection that allows voltages up to ±40 V beyond either supply rail (e.g., −VS + 40 V on −IN, +VS − 40 V on +IN) without damage or latch-up. This is achieved through integrated protection structures that clamp excess voltage while maintaining ultralow input bias current (<0.5 nA) and noise performance. Unlike discrete diode clamps, this on-chip protection does not degrade CMRR or introduce leakage paths-enabling direct connection to industrial field sensors without external protection components.