Part A
AD8429ARZ
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 7143 PCS
- Package
- SOIC-8
- Series
- Linear - Amplificadores - Instrumentação, OP Amps, Buffer Amps
Replacement verdict
Compatible functional replacement candidate
The AD8429ARZ and AD8422BRZ-RL are both precision instrumentation amplifiers from Analog Devices in the same SOIC-8 package, sharing a common functional role and pin-compatible footprint. However, they differ in key electrical characteristics such as gain bandwidth, noise performance, and supply range, so the AD8422BRZ-RL should be treated as a functional candidate rather than a guaranteed drop-in replacement. Designers must validate gain, bandwidth, and noise requirements against the target application before substituting.
Package Type
High match
Amplifier Function
High match
Gain Bandwidth Product
Validation required
Input Voltage Noise
Validation required
Parts at a glance
Part B
AD8422BRZ-RL
Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 7470 PCS
- Package
- SOIC-8
- Series
- Linear - Amplificadores - Instrumentação, OP Amps, Buffer Amps
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 | AD8422BRZ-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 | 2.2 MHz | Higher GBW allows the AD8429 to handle wider signal bandwidths, which is critical for high-speed signal conditioning. |
| Input Voltage Noise (1 kHz) | 1 nV/√Hz | 8 nV/√Hz | Lower input noise improves measurement resolution for low-level signals; the AD8429 is significantly quieter. |
| Input Offset Voltage (max) | 50 µV | 70 µV | Lower offset voltage reduces DC error in precision measurement applications. |
| Supply Voltage Range | ±4 V to ±18 V | ±2.3 V to ±18 V | The AD8422 supports lower supply voltages, enabling use in low-power or battery-operated systems. |
| Quiescent Supply Current | 6.5 mA | 0.3 mA | The AD8422 draws far less current, making it preferable for power-sensitive designs. |
| CMRR (G=100, DC) | 126 dB | 120 dB | Higher common-mode rejection improves accuracy in the presence of common-mode noise and interference. |
| Operating Temperature Range | -40 °C to +125 °C | -40 °C to +85 °C | The AD8429 supports a wider temperature range, suitable for harsher industrial environments. |
| 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 | AD8422BRZ-RL |
|---|---|---|
| Supplier | - | Analog Devices Inc. |
| Part Status | Active | Active |
| Amplifier Type | Instrumentation | Instrumentation |
| Number of Circuits | 1 | 1 |
| Output Type | - | Rail-to-Rail |
| Slew Rate | 22V/µs | 0.8V/µs |
| -3 dB Bandwidth | 15 MHz | 2.2 MHz |
| Current - Input Bias | 300 nA | 200 pA |
| Voltage - Input Offset | 150 µV | 25 µV |
| Supply Current | 6.7mA | 300µA |
| Current - Output / Channel | 35 mA | 20 mA |
| Voltage - Supply Span(Min) | 8 V | 4.6 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 AD8422BRZ-RL?
The AD8429ARZ is a low-noise instrumentation amplifier optimized for high gain and low noise (1 nV/√Hz) with a gain range of 1 to 10,000, supplied in an 8-lead SOIC package. The AD8422BRZ-RL is a high-precision, low-power instrumentation amplifier with lower supply current and rail-to-rail output, supplied in an 8-lead SOIC and provided in tape-and-reel packaging. The AD8429ARZ is specified for ±4 V to ±18 V dual supplies, while the AD8422BRZ-RL operates from ±2.3 V to ±18 V (or 4.6 V to 36 V single supply).
Can the AD8429ARZ and AD8422BRZ-RL be used interchangeably in an existing design?
No, they are not pin-for-pin or specification-for-specification drop-in replacements. Although both are 8-lead SOIC instrumentation amplifiers, their gain-setting resistor formulas, supply voltage ranges, output swing characteristics, and noise/bandwidth specifications differ. A direct substitution requires revalidation of gain accuracy, supply rails, output headroom, and stability against the manufacturer datasheets.
Which device offers lower input voltage noise?
The AD8429ARZ specifies an input voltage noise density of approximately 1 nV/√Hz at 1 kHz, making it the lower-noise option of the two. The AD8422BRZ-RL specifies an input voltage noise density of approximately 8 nV/√Hz at 1 kHz. Designs prioritizing low noise should therefore favor the AD8429ARZ.
How do the supply voltage and power consumption requirements compare?
The AD8429ARZ operates on dual supplies from ±4 V to ±18 V and draws a typical quiescent supply current of about 4.5 mA. The AD8422BRZ-RL operates on dual supplies from ±2.3 V to ±18 V (or 4.6 V to 36 V single supply) and draws a typical quiescent supply current of about 300 µA, making it significantly lower power and suitable for battery-powered or low-power systems.
What are the gain-setting configurations for each device?
Both devices set gain using a single external resistor connected between the RG pins. For the AD8429ARZ, gain is set by G = 1 + (6 kΩ / RG). For the AD8422BRZ-RL, gain is set by G = 1 + (19.8 kΩ / RG). Because the internal gain resistors differ, the same RG value produces different gains on each device, so gain resistors must be recalculated when comparing or substituting.
Which device provides rail-to-rail output swing?
The AD8422BRZ-RL features a rail-to-rail output that swings to within tens of millivolts of the supply rails, which is beneficial for low-voltage or single-supply designs. The AD8429ARZ does not provide rail-to-rail output; its output swing is limited relative to the supply rails, so output headroom must be verified for the intended signal range.
What are the bandwidth and gain range specifications for each amplifier?
The AD8429ARZ provides a gain range of 1 to 10,000 with a -3 dB bandwidth of approximately 15 MHz at G = 1 and about 1.2 MHz at G = 100. The AD8422BRZ-RL provides a gain range of 1 to 1,000 with a -3 dB bandwidth of approximately 2.2 MHz at G = 1 and about 200 kHz at G = 100. The AD8429ARZ therefore offers higher bandwidth at comparable gains.
What packaging and ordering differences should a procurement engineer note?
The AD8429ARZ is supplied in an 8-lead SOIC package in tube or standard reel quantities depending on the ordering suffix. The AD8422BRZ-RL is supplied in an 8-lead SOIC in tape-and-reel packaging, as indicated by the -RL suffix. Both are RoHS-compliant per their respective manufacturer datasheets, but reel size, moisture sensitivity level, and minimum order quantities should be confirmed against the specific ordering guide.