Part A
AD8429BRZ
Analog Equipment GmbH.
- Lifecycle
- Active
- Stock
- 6879 PCS
- Package
- SOIC-8
- Series
- Amplificateurs linéaires - instruments, amplificateurs opérationnels, amplificateurs tampons
Replacement verdict
Compatible functional replacement candidate
The AD8429BRZ and AD8421ARZ-RL are both precision instrumentation amplifiers from Analog Devices sharing a functionally equivalent architecture, making the AD8421ARZ-RL a viable functional replacement candidate for the AD8429BRZ in many designs. However, the two parts differ in gain-bandwidth, noise performance, and specified gain range, so the substitution should be validated against the target application's bandwidth, noise, and gain requirements before adoption.
Gain Bandwidth Product
Validation required
Input Voltage Noise
Validation required
Package Type
High match
Supply Voltage Range
Validation required
Parts at a glance
Part B
AD8421ARZ-RL
Analog Equipment GmbH.
- Lifecycle
- Active
- Stock
- 4538 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 | AD8429BRZ | AD8421ARZ-RL | Why it matters |
|---|---|---|---|
| Number of Channels | 1 | 1 | Both are single-channel instrumentation amplifiers, so channel count is functionally equivalent. |
| Gain Bandwidth Product (GBW) | 15 MHz | 10 MHz | Higher GBW allows the amplifier to maintain gain at higher signal frequencies, affecting bandwidth in high-speed applications. |
| Input Voltage Noise (1 kHz) | 1 nV/√Hz | 3 nV/√Hz | Lower input voltage noise improves signal-to-noise ratio for low-level sensor signals. |
| Input Offset Voltage (max) | 50 µV | 60 µV | Lower offset voltage reduces DC error and improves accuracy in precision measurement systems. |
| Input Bias Current (max) | 100 nA | 500 pA | Much lower bias current in the AD8421 reduces errors with high-impedance sources and in precision DC applications. |
| CMRR (G=100, DC to 60 Hz) | 126 dB | 114 dB | Higher common-mode rejection suppresses interference from common-mode voltages, critical in noisy industrial environments. |
| Supply Voltage Range | ±4 V to ±18 V | ±2.5 V to ±18 V | The AD8421 supports lower supply voltages, enabling use in low-voltage or battery-powered systems. |
| Quiescent Supply Current (max) | 6.5 mA | 2.3 mA | Lower quiescent current in the AD8421 reduces power consumption, important for portable and power-sensitive designs. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +85 °C | The wider temperature range of the AD8429 suits harsher environments and higher-temperature applications. |
| 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 | AD8429BRZ | AD8421ARZ-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 | 150 nA | 1 nA |
| Voltage - Input Offset | 50 µV | 60 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 AD8429BRZ and the AD8421ARZ-RL?
The AD8429BRZ is a low-noise instrumentation amplifier optimized for ultra-low noise (1 nV/√Hz) with a gain range of 1 to 10,000, supplied in an 8-lead SOIC package. The AD8421ARZ-RL is a lower-power, lower-cost instrumentation amplifier with 3 nV/√Hz noise, a gain range of 1 to 10,000, and is supplied in an 8-lead SOIC package in tape-and-reel form. The AD8429BRZ is specified for a wider operating temperature range of −40°C to +125°C, while the AD8421ARZ-RL is specified for −40°C to +85°C.
Are the AD8429BRZ and AD8421ARZ-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 them to share the same PCB footprint, though electrical performance differences must be evaluated for the target application.
Which device has lower input voltage noise?
The AD8429BRZ has a lower input voltage noise density of 1 nV/√Hz at 1 kHz, compared to 3 nV/√Hz at 1 kHz for the AD8421ARZ-RL. The AD8429BRZ is therefore better suited for very low-level signal amplification where noise is critical.
How do the gain-setting configurations compare between the two parts?
Both the AD8429BRZ and AD8421ARZ-RL use a single external resistor (RG) to set gain from 1 to 10,000, with the gain equation G = 1 + (6 kΩ / RG) for the AD8429BRZ and G = 1 + (9.9 kΩ / RG) for the AD8421ARZ-RL. Because the internal RG values differ, the same external resistor produces different gains on each device.
What are the supply voltage and quiescent current specifications for each device?
The AD8429BRZ operates from ±4 V to ±18 V dual supplies and draws a typical quiescent current of 4.5 mA. The AD8421ARZ-RL operates from ±2.25 V to ±18 V dual supplies and draws a typical quiescent current of 2.3 mA, making it the lower-power option.
Do both devices support the same operating temperature range?
No. The AD8429BRZ is specified over the −40°C to +125°C industrial temperature range, while the AD8421ARZ-RL is specified over the −40°C to +85°C temperature range. Designs requiring operation above +85°C should use the AD8429BRZ.
What is the difference in packaging and ordering format?
The AD8429BRZ is supplied in an 8-lead SOIC tube format (BRZ grade). The AD8421ARZ-RL is supplied in an 8-lead SOIC tape-and-reel format (ARZ grade, RL suffix), which is suited to automated high-volume assembly. Both use the same SOIC body size and pinout.