Analog Devices Inc. AD8429BRZ

Overview

AD8429BRZ from Analog Devices is an ultralow-noise instrumentation amplifier optimized for precision dc-coupled signal conditioning in harsh environments. It delivers 1 nV/√Hz input voltage noise, 90 dB minimum CMRR at G = 1, and ±50 µV max input offset voltage over −40°C to +125°C - enabling high-fidelity measurement of microvolt-level biopotentials and strain gauge outputs.

For engineers reviewing the AD8429BRZ datasheet, AD8429BRZ pinout, AD8429BRZ application, or AD8429BRZ equivalent, key selection criteria include its current-feedback architecture enabling 1.2 MHz bandwidth at G = 100, single-resistor gain setting (G = 1 to 10,000), and reference pin for output level shifting into single-supply ADCs.

Technical Context

The AD8429BRZ implements a classic 3-op-amp topology with current-feedback preamplifier stage and precision difference amplifier output stage. Its gain-setting architecture replicates differential input voltage across RG, enabling accurate gain control independent of common-mode voltage.

CMRR increases with gain (134 dB typical at G = 1000) and remains ≥80 dB up to 5 kHz at G = 1. The reference terminal provides unity-gain level-shifting capability with ≤0.05% reference gain error, supporting direct interfacing to rail-to-rail ADCs without external level translation.

Key Specifications

Pinout & Package

AD8429BRZ is housed in an 8-lead plastic SOIC package (JEDEC MS-012, 150 mil width) with θ_JA = 121°C/W. Pin layout prioritizes input symmetry and supply decoupling proximity.

Key Features

Applications

Equivalent & Alternatives

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

Compared with INA128UA and AD8421ARZ, AD8429BRZ uniquely combines ultralow 1 nV/√Hz noise, integrated reference pin for single-supply compatibility, and guaranteed −40°C to +125°C operation - making it optimal for compact, battery-powered, or high-temperature embedded instrumentation where board space and supply flexibility are constrained.

Availability

AD8429BRZ is available at Aetrix Electronics and suitable for medical instrumentation, precision data acquisition, and vibration analysis requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for AD8429BRZ 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, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Norwood, MA.

The AD8429BRZ belongs to Analog Devices' precision instrumentation amplifier product line, engineered specifically for demanding low-noise, high-CMRR, wide-temperature applications in medical diagnostics, industrial sensing, and test equipment.

FAQ

What is the maximum gain achievable with AD8429BRZ?

The AD8429BRZ supports gain settings from G = 1 to G = 10,000 using a single external resistor across pins 2 and 3, calculated as G = 1 + (6 kΩ/R_G). At G = 10,000, the required R_G is 0.604 Ω; practical implementation requires careful attention to resistor power rating and parasitic inductance. The AD8429BRZ maintains specified performance across this full range when using 1% metal-film resistors.

Does AD8429BRZ require external components for basic operation?

AD8429BRZ operates at G = 1 with no external components. For gain >1, only a single precision resistor across RG pins (2 and 3) is required. External 0.1 µF ceramic bypass capacitors at +VS and −VS pins are mandatory for stability and PSRR performance. A low-impedance source (<1 Ω) is required at the REF pin if used for level shifting; no external compensation or feedback networks are needed.

How does the reference pin (REF) function in AD8429BRZ?

The REF pin in AD8429BRZ sets the output common-mode voltage with unity gain: V_OUT = G × (V_+IN − V_−IN) + V_REF. It enables direct interfacing to single-supply ADCs by shifting the output to mid-supply (e.g., 2.5 V with ±5 V supplies). The AD8429BRZ specifies ≤0.05% reference gain error and requires a source impedance <1 Ω to prevent CMRR degradation caused by interaction with the internal 5 kΩ reference resistor.

What is the small-signal bandwidth of AD8429BRZ at G = 100?

The AD8429BRZ delivers 1.2 MHz small-signal bandwidth (−3 dB) at G = 100, as verified in the datasheet's Figure 9 and Table 1. This bandwidth is enabled by its current-feedback architecture, which avoids the gain-bandwidth trade-off typical of voltage-feedback instrumentation amplifiers. Performance holds across the full −40°C to +125°C operating range, with minimal variation (<±5%) in bandwidth over temperature.

Can AD8429BRZ be used with single-supply operation?

AD8429BRZ requires dual supplies (±4 V to ±18 V) for internal circuitry operation and cannot run on true single supply (e.g., 0 V and +5 V). However, its REF pin enables output level shifting to interface with single-supply ADCs - for example, tying REF to +2.5 V while operating from ±5 V supplies produces an output centered at 2.5 V with ±2.3 V swing. Input common-mode range remains symmetric about ground, so signal sources must be referenced accordingly.