Analog Devices Inc. AD621ARZ

Overview

AD621ARZ from Analog Devices is a precision bipolar-input instrumentation amplifier optimized for low-drift, low-noise signal conditioning in bridge and transducer interfaces. It delivers pin-strappable gains of 10 or 100, 0.15% max total gain error, 5 ppm/°C gain drift, 125 µV max RTI offset voltage, and 9 nV/√Hz input voltage noise at 1 kHz - enabling high-accuracy weigh-scale and industrial process control systems.

For engineers reviewing the AD621ARZ datasheet, AD621ARZ pinout, AD621ARZ application, or AD621ARZ equivalent, key selection criteria include guaranteed total system error specs (gain error, offset, drift), dual-gain flexibility via Pin 1–8 strap, SOIC-8 package compatibility with space-constrained PCBs, and verified performance at ±2.3 V to ±18 V supplies across –40°C to +85°C.

Technical Context

The AD621ARZ implements a monolithic three-op-amp architecture with on-chip laser-trimmed thin-film gain resistors, enabling precise fixed gains of 10 (default) or 100 (via Pin 1–8 short). Its Superβeta bipolar input stage achieves 1.5 nA max input bias current while maintaining 10² GΩ differential input impedance.

Gain-setting is fully internalized: no external resistors are required for G = 10 or 100. The reference pin (Pin 6) supports active offset injection and ground-loop mitigation, and the output stage delivers rail-to-rail compatible swing (e.g., ±13.8 V @ ±15 V supply, RL = 10 kΩ).

Key Specifications

Pinout & Package

AD621ARZ is supplied in an 8-lead SOIC (R-8) package, measuring 4.9 mm × 3.9 mm × 1.75 mm, with standard JEDEC MS-012AC footprint and 1.27 mm pitch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with INA128UA and AD8421ARMZ, AD621ARZ uniquely balances dual-gain flexibility, guaranteed total system error, SOIC-8 footprint, and sub-1.5 mA power - making it optimal for cost-sensitive, space-constrained industrial and portable measurement systems requiring G = 10 or 100 without design overhead.

Availability

AD621ARZ is available at Aetrix Electronics and suitable for weigh scales, transducer interface circuits, and battery-powered portable equipment requiring stable component supply, long-term lifecycle support, and RoHS-compliant sourcing.

Supply support for AD621ARZ 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, serving industrial, automotive, communications, and healthcare markets since 1965.

The AD621ARZ belongs to Analog Devices' precision instrumentation amplifier product line, designed specifically for high-accuracy, low-power signal conditioning in bridge-based sensors and industrial measurement systems.

FAQ

What gain options does the AD621ARZ support, and how are they configured?

The AD621ARZ supports two precision gains: G = 10 (default, Pins 1 and 8 open) and G = 100 (configured by shorting Pins 1 and 8). No external resistors are required. This pin-strappable method avoids tolerance and thermal tracking errors associated with discrete gain networks. The AD621ARZ's internal laser-trimmed resistors ensure 0.15% max gain error and 5 ppm/°C drift at both settings.

Can the AD621ARZ operate from a single 5 V supply, and what are the input/output voltage limitations?

Yes, the AD621ARZ operates from a single 5 V supply (i.e., +VS = +5 V, –VS = GND). Input common-mode range is –0.1 V to +3.8 V (–VS + 1.9 V to +VS – 1.2 V), and output swing is +0.9 V to +3.8 V (–VS + 1.1 V to +VS – 1.2 V) with 10 kΩ load. These rails allow direct interfacing with 5 V microcontrollers and 16-bit ADCs without level-shifting circuitry.

How does the reference pin (Pin 6) function in the AD621ARZ, and what design benefits does it provide?

The REF pin of the AD621ARZ sets the output DC offset voltage. When grounded, output is centered at 0 V. Applying a voltage (e.g., 2.5 V) shifts output accordingly. This enables zero-suppression in bridge circuits, floating-load interfacing, and ground-loop elimination. Unlike AC-coupling, REF-based offset removal introduces no time constant, preserving low-frequency fidelity down to DC.

What is the maximum continuous input overvoltage the AD621ARZ can withstand, and how is protection implemented?

The AD621ARZ withstands ±3.0 V continuous differential input overvoltage with power on or off, thanks to integrated 400 Ω thin-film series resistors (R3/R4) and input transistor protection diodes. This protects against transducer faults, cable shorts, and supply sequencing errors. External 2 kΩ resistors raise tolerance to ±15 V while increasing input noise only to 15 nV/√Hz - still competitive with discrete three-op-amp designs.

Is the AD621ARZ suitable for high-impedance sensor sources, and what are its input bias current specifications?

Yes - the AD621ARZ uses Superβeta bipolar input transistors, achieving 1.5 nA max input bias current over –40°C to +85°C and 0.5 nA typical at 25°C. Its 10² GΩ differential input impedance minimizes loading error on high-Z sources like piezoresistive pressure sensors and thermopiles. Input offset current is 1.0 nA max, ensuring minimal error from mismatched source impedances.