Part A
AD8429ARZ
Analog Equipment GmbH.
- Lifecycle
- Active
- Stock
- 7143 PCS
- Package
- SOIC-8
- Series
- Amplificateurs linéaires - instruments, amplificateurs opérationnels, amplificateurs tampons
Replacement verdict
Compatible functional replacement candidate
The AD8429ARZ and AD8421BRZ-RL are both precision instrumentation amplifiers from Analog Devices sharing a common SOIC-8 footprint and similar gain-setting architecture, making the AD8421BRZ-RL a viable functional replacement candidate for the AD8429ARZ in many low-noise signal-conditioning designs. However, the two parts differ in gain-bandwidth, noise density, and supply range, so the designer must validate bandwidth, noise budget, and supply headroom against the target application before committing to the substitution.
Package and Pinout
High match
Gain Bandwidth Product
Validation required
Input Voltage Noise
Validation required
Supply Voltage Range
Validation required
Parts at a glance
Part B
AD8421BRZ-RL
Analog Equipment GmbH.
- Lifecycle
- Active
- Stock
- 9374 PCS
- Package
- SOIC-8
- Series
- Amplificateurs linéaires - instruments, amplificateurs opérationnels, amplificateurs tampons
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | AD8429ARZ | AD8421BRZ-RL | Why it matters |
|---|---|---|---|
| Gain Bandwidth Product (GBW) | 1.2 MHz (G = 100) | 10 MHz (G = 100) | Higher bandwidth allows the amplifier to handle faster signals and preserves signal fidelity at higher frequencies, which is critical for dynamic measurements. |
| Input Voltage Noise (1 kHz) | 1 nV/√Hz | 3 nV/√Hz | Lower input voltage noise improves the signal-to-noise ratio for low-level signals, which is essential in precision sensor and instrumentation applications. |
| Input Offset Voltage (max) | 50 µV | 60 µV | Lower offset voltage reduces DC error at the output, improving accuracy in high-gain precision measurement systems. |
| Input Bias Current (max) | 150 nA | 500 pA | Much lower bias current minimizes errors when interfacing with high-impedance sources, making the part suitable for sensors with large source impedance. |
| CMRR (G = 1, DC to 60 Hz) | 80 dB | 94 dB | Higher common-mode rejection suppresses interference and noise from the input environment, improving measurement accuracy in noisy industrial settings. |
| Supply Voltage Range | ±4 V to ±18 V | ±2.5 V to ±18 V | A wider low-end supply range enables operation in lower-voltage systems, affecting compatibility with modern low-power signal chains. |
| Quiescent Supply Current (max) | 4.5 mA | 2.3 mA | Lower quiescent current reduces power consumption, which is important for portable and power-constrained instrumentation designs. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +85 °C | A wider temperature range supports reliable operation in harsh environments and industrial applications with elevated ambient temperatures. |
| Package | 8-Lead SOIC | 8-Lead SOIC | Identical package and pinout allow direct board-level substitution without layout changes. |
Need help validating a replacement?
Send your BOM and application constraints for technical and sourcing review.
Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD8429ARZ | AD8421BRZ-RL |
|---|---|---|
| Supplier | - | Analog Devices Inc. |
| Part Status | Active | Active |
| Amplifier Type | Instrumentation | Instrumentation |
| Number of Circuits | 1 | 1 |
| Slew Rate | 22V/µs | 35V/µs |
| -3 dB Bandwidth | 15 MHz | 10 MHz |
| Current - Input Bias | 300 nA | 100 pA |
| Voltage - Input Offset | 150 µV | 25 µV |
| Supply Current | 6.7mA | 2mA |
| Current - Output / Channel | 35 mA | 65 mA |
| Voltage - Supply Span(Min) | 8 V | 5 V |
| Voltage - Supply Span(Max) | 36 V | 36 V |
| Operating Temperature | -40°C ~ 125°C | -40°C ~ 85°C |
| Mounting Type | Surface Mount | Surface Mount |
Frequently asked questions
What are the primary differences between the AD8429ARZ and AD8421BRZ-RL?
The AD8429ARZ is a low-noise instrumentation amplifier with a gain range of 1 to 10,000, a typical input voltage noise of 1 nV/√Hz at 1 kHz, and a specified gain error of 0.02% at G=1. The AD8421BRZ-RL is a lower-power instrumentation amplifier with a typical input voltage noise of 3 nV/√Hz at 1 kHz, a gain range of 1 to 10,000, and a specified gain error of 0.05% at G=1. The AD8429ARZ is supplied in an 8-lead SOIC package, while the AD8421BRZ-RL is supplied in an 8-lead SOIC package in tape and reel format.
Are the AD8429ARZ and AD8421BRZ-RL pin-compatible?
Yes. Both devices are offered in an 8-lead SOIC package with the same pinout: -IN, +IN, -VS, +VS, REF, OUT, and RG pins. This allows for a common PCB footprint, but electrical differences must be validated before substitution.
Which device has lower input voltage noise?
The AD8429ARZ has a lower typical input voltage noise of 1 nV/√Hz at 1 kHz, compared to 3 nV/√Hz at 1 kHz for the AD8421BRZ-RL. The AD8429ARZ is therefore better suited for low-noise signal acquisition applications.
How do the gain-setting resistor requirements compare?
Both devices use a single external resistor RG to set gain according to the formula G = 1 + (49.4 kΩ / RG). The AD8429ARZ and AD8421BRZ-RL share the same gain equation, so the same RG value produces the same nominal gain for both parts.
What are the supply voltage and quiescent current specifications?
Both the AD8429ARZ and AD8421BRZ-RL operate from dual supplies of ±4 V to ±18 V. The AD8429ARZ has a typical quiescent current of 6.5 mA, while the AD8421BRZ-RL has a typical quiescent current of 2.3 mA, making the AD8421BRZ-RL more suitable for power-sensitive designs.
Do both devices support the same operating temperature range?
Yes. Both the AD8429ARZ and AD8421BRZ-RL are specified for operation over the industrial temperature range of -40°C to +85°C.
What is the difference in gain error and gain drift?
The AD8429ARZ specifies a gain error of 0.02% at G=1 and a gain drift of 10 ppm/°C. The AD8421BRZ-RL specifies a gain error of 0.05% at G=1 and a gain drift of 10 ppm/°C. The AD8429ARZ offers tighter initial gain accuracy, while gain drift is comparable between the two devices.
Can the AD8421BRZ-RL be used as a drop-in replacement for the AD8429ARZ?
Pin compatibility and the shared gain equation allow a common footprint, but the AD8421BRZ-RL has higher input voltage noise (3 nV/√Hz vs 1 nV/√Hz at 1 kHz) and lower quiescent current (2.3 mA vs 6.5 mA). A replacement should only be made after verifying that the higher noise and different supply current meet the target design requirements using the respective manufacturer datasheets.