Part A
AD8429ARZ
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 7143 Stückzahl
- Package
- SOIC-8
- Series
- Linear-Verstärker.Instrumentation, OP-Verstärker, Pufferverstärker
Replacement verdict
Compatible functional replacement candidate
The AD8429ARZ and AD8421ARZ-RL are both precision instrumentation amplifiers in the same SOIC-8 package with identical pinout, making them strong functional replacement candidates. However, they differ in gain range, bandwidth, and noise performance, so the AD8421ARZ-RL should be validated against the specific gain, frequency, and noise requirements of the target design before substitution.
Package Type
High match
Pin Configuration
High match
Gain Range
Validation required
Bandwidth and Noise
Validation required
Parts at a glance
Part B
AD8421ARZ-RL
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 4538 Stückzahl
- Package
- SOIC-8
- Series
- Linear-Verstärker.Instrumentation, OP-Verstärker, Pufferverstärker
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 | AD8421ARZ-RL | Why it matters |
|---|---|---|---|
| Input Voltage Noise (1 kHz, typ) | 1 nV/√Hz | 3 nV/√Hz | Lower input voltage noise improves signal-to-noise ratio for low-level sensor signals, making the AD8429 preferable for very low-noise applications. |
| Gain Bandwidth Product (G = 1, typ) | 15 MHz | 10 MHz | Higher bandwidth supports wider signal frequency ranges and faster settling, affecting dynamic performance in instrumentation front ends. |
| Input Offset Voltage (max, RTI) | 50 µV | 60 µV | Lower offset voltage reduces DC error at the output, important for precision measurement and high-gain amplification. |
| Input Bias Current (max) | 100 nA | 500 pA | Much lower bias current in the AD8421 minimizes errors with high source impedances, making it better suited for high-impedance sensors. |
| CMRR (G = 100, min) | 120 dB | 114 dB | Higher common-mode rejection suppresses interference and ground noise, critical for extracting small differential signals in noisy environments. |
| Supply Current (max) | 4.5 mA | 2.3 mA | Lower supply current in the AD8421 reduces power consumption, beneficial for portable and power-constrained designs. |
| Supply Voltage Range | ±4 V to ±18 V | ±2.5 V to ±18 V | The wider low-end supply range of the AD8421 allows operation at lower supply voltages, enabling use in low-voltage systems. |
| Operating Temperature Range | −40°C to +125°C | −40°C to +85°C | The extended upper temperature range of the AD8429 supports 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 | AD8429ARZ | 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 | 300 nA | 1 nA |
| Voltage - Input Offset | 150 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 key differences between the AD8429ARZ and AD8421ARZ-RL?
The AD8429ARZ is a low-noise instrumentation amplifier optimized for ultra-low noise (1 nV/√Hz) with a gain range of 1 to 10,000, while the AD8421ARZ-RL is a lower-power, lower-cost instrumentation amplifier with 3 nV/√Hz noise and a gain range of 1 to 10,000. The AD8421ARZ-RL is supplied in tape-and-reel packaging (RL suffix), whereas the AD8429ARZ is typically supplied in tubes. Both are available in 8-lead SOIC packages.
Are the AD8429ARZ and AD8421ARZ-RL pin-compatible?
Yes, both devices are offered in an 8-lead SOIC package with the same pinout (gain resistor pins, +IN, -IN, +VS, -VS, REF, and OUT), allowing them to share the same PCB land pattern. However, designers should verify the specific package variant and thermal considerations against the respective datasheets before substitution.
How do the noise specifications of the AD8429ARZ and AD8421ARZ-RL compare?
The AD8429ARZ has an input voltage noise density of approximately 1 nV/√Hz at 1 kHz, making it suitable for ultra-low-noise applications. The AD8421ARZ-RL has an input voltage noise density of approximately 3 nV/√Hz at 1 kHz. The AD8429ARZ therefore offers lower noise, while the AD8421ARZ-RL provides a balance of lower power consumption and cost.
What are the supply voltage and quiescent current differences between the two parts?
Both devices operate from dual supplies typically ranging from ±2.25 V to ±18 V (or single-supply equivalents). The AD8429ARZ draws a typical quiescent current of about 4.5 mA, while the AD8421ARZ-RL draws a lower typical quiescent current of about 2.3 mA, making the AD8421ARZ-RL preferable for power-sensitive designs.
What is the significance of the "RL" suffix on the AD8421ARZ-RL?
The "RL" suffix indicates tape-and-reel packaging, which is intended for automated pick-and-place assembly in high-volume production. The AD8429ARZ without an RL suffix is typically supplied in tube packaging. Both are the same die and performance grade; only the packaging format differs.
Can the AD8421ARZ-RL be used as a drop-in replacement for the AD8429ARZ in low-noise designs?
Because the AD8421ARZ-RL has higher input voltage noise (approximately 3 nV/√Hz versus 1 nV/√Hz), it is not a direct drop-in replacement in designs where the ultra-low noise floor of the AD8429ARZ is critical. In applications where 3 nV/√Hz noise is acceptable and lower power is desired, the AD8421ARZ-RL may be considered after validating gain, bandwidth, and CMRR requirements against the datasheets.
How do the gain-setting configurations compare between the AD8429ARZ and AD8421ARZ-RL?
Both devices use a single external resistor between the RG pins to set gain, with the gain equation G = 1 + (6 kΩ / RG) for the AD8429ARZ and G = 1 + (9.9 kΩ / RG) for the AD8421ARZ-RL. Designers must recalculate the gain resistor value when substituting between the two parts.
What are the bandwidth and CMRR characteristics of each device?
The AD8429ARZ offers a -3 dB bandwidth of approximately 1.2 MHz at G = 1 and CMRR of about 90 dB at G = 1 (DC to 60 Hz). The AD8421ARZ-RL offers a -3 dB bandwidth of approximately 10 MHz at G = 1 and CMRR of about 80 dB at G = 1. The AD8421ARZ-RL provides wider bandwidth, while the AD8429ARZ provides higher CMRR at low gain.