AD8421ARZ - 3nV/√Hz Low Power In-Amp | Analog Devices
MPN: AD8421ARZ ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $5.29 | $5.29 |
| 10 | $4.76 | $47.60 |
| 100 | $4.23 | $423.00 |
| 500 | $3.81 | $1,905.00 |
| 1,000 | $3.39 | $3,390.00 |
Drop-in alternatives for AD8421ARZ — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
AD8421BRZ
✅ Drop-In✓ In Stock
$4.9 / Unit
View Datasheet →AD8421ARZ-R7
✅ Drop-In📋 Reference alternative (not in catalog)
AD8421ARZ-RL
✅ Drop-In📋 Reference alternative (not in catalog)
AD8221ARZ
✅ Drop-In✓ In Stock
$3.29 / Unit
View Datasheet →INA128
✅ Drop-In📋 Reference alternative (not in catalog)
AD8421ARZ Maximum Ratings & Electrical Characteristics
| Amplifier Type | Instrumentation Amplifier |
| Number of Circuits | 1 |
| Input Offset Voltage | 60 µV |
| Slew Rate | 35 V/µs |
| Bandwidth | 10 MHz |
| Supply Voltage Range | 5 V to 36 V |
| Voltage Noise Density | 3 nV/√Hz |
| Bias Current | Ultralow (exact value [DATA_NEEDED: Input Bias Current]) |
| Common-Mode Rejection Ratio | [DATA_NEEDED: CMRR] |
| Operating Temperature Range | -40°C to +85°C |
| Package | 8-SOIC |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant |
| Reference Pin | Yes |
| Supply Current | [DATA_NEEDED: Supply Current] |
AD8421ARZ Pin Configuration
| Pin 1 | -IN — Inverting input |
| Pin 2 | RG — Gain setting resistor |
| Pin 3 | RG — Gain setting resistor |
| Pin 4 | -VS — Negative supply |
| Pin 5 | REF — Reference voltage for output offset |
| Pin 6 | OUT — Output |
| Pin 7 | +VS — Positive supply |
| Pin 8 | +IN — Non-inverting input |
Safe Operating Area (SOA) & Thermal Characteristics
No official SOA curve available for this component. Always operate within absolute maximum ratings specified in the datasheet. Ensure adequate cooling and derate as needed.
Typical Applications
AD8421ARZ is suitable for 6 applications: Medical Instrumentation, Industrial Process Control, Data Acquisition Systems, Transducer Interfaces, Battery-Powered Instruments, High-Speed Signal Conditioning.
Medical Instrumentation
The AD8421ARZ is ideal for medical instrumentation such as ECG and EEG due to its low noise (3 nV/√Hz) and high CMRR. It amplifies small biopotential signals while rejecting common-mode interference from the body and power lines. Its low bias current minimizes loading on high-impedance electrodes, and its wide supply range (5V to 36V) accommodates battery or mains-powered designs. The high bandwidth (10 MHz) ensures faithful reproduction of fast signal transients, while the reference pin allows precise output level shifting for single-supply operation.
Recommended
Industrial Process Control
In industrial process control, the AD8421ARZ provides accurate signal conditioning for sensors like strain gauges and pressure transducers. Its low offset voltage (60 µV) and low noise ensure precise measurement of small signals in noisy industrial environments. The high common-mode rejection rejects interference from motors and power lines, while the wide supply range (up to 36V) allows direct operation from industrial 24V rails. The 10 MHz bandwidth supports fast control loops, and the low power consumption reduces heat in enclosures. The SOIC package is easy to integrate into existing PCB designs.
Recommended
Data Acquisition Systems
The AD8421ARZ is well-suited for data acquisition systems requiring high-speed, low-noise signal conditioning. Its 10 MHz bandwidth and 35 V/µs slew rate allow it to accurately amplify fast transients, making it ideal for digitizing dynamic signals. The low noise (3 nV/√Hz) preserves signal integrity, and the low bias current minimizes errors when interfacing with high-impedance sources. The reference pin enables precise offset adjustment, which is useful for bipolar-to-unipolar conversion. The device operates from 5V to 36V, making it compatible with a wide range of ADC supplies.
Recommended
Transducer Interfaces
The AD8421ARZ is an excellent choice for transducer interfaces, such as thermocouple and RTD signal conditioning. Its ultralow bias current minimizes errors from high-impedance sources, and its low noise (3 nV/√Hz) ensures accurate temperature measurement. The high common-mode rejection rejects interference from power lines and motors, while the wide supply range (5V to 36V) allows operation from various power rails. The 10 MHz bandwidth is more than sufficient for temperature sensing, and the low power consumption is beneficial for portable instruments. The reference pin allows easy offset calibration.
Recommended
Battery-Powered Instruments
The AD8421ARZ is ideal for battery-powered instruments due to its low power consumption and wide supply range (5V to 36V). It can operate directly from a 9V battery or a 3.3V supply with proper configuration. The low noise (3 nV/√Hz) ensures accurate measurements, and the low bias current extends battery life by minimizing current draw from sensors. The 10 MHz bandwidth supports fast sampling, while the SOIC package is compact and lightweight. The reference pin allows output level shifting for single-supply operation, making it easy to interface with ADCs.
Recommended
High-Speed Signal Conditioning
The AD8421ARZ is designed for high-speed signal conditioning applications, such as vibration analysis and high-frequency sensor interfaces. Its 10 MHz bandwidth and 35 V/µs slew rate allow it to amplify fast transients without distortion. The low noise (3 nV/√Hz) preserves signal fidelity, and the high common-mode rejection rejects interference in noisy environments. The device operates from 5V to 36V, making it suitable for a variety of supply rails. The SOIC package is easy to integrate into high-speed PCB layouts, and the reference pin allows precise offset control.
Recommended
Recommended Products Summary
Engineering reference data for AD8421ARZ — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | AD8421BRZ | AD8221ARZ | INA128 |
|---|---|---|---|---|
| Package | 8-SOIC | 8-SOIC | 8-SOIC | 8-SOIC |
| Brand | Analog Devices | Analog Devices | Analog Devices | Texas Instruments |
| Voltage Noise Density | 3 nV/√Hz | 3 nV/√Hz | 8 nV/√Hz | 8 nV/√Hz |
| Bandwidth | 10 MHz | 10 MHz | 1 MHz | 200 kHz |
| Slew Rate | 35 V/µs | 35 V/µs | 2 V/µs | 0.4 V/µs |
| Input Offset Voltage | 60 µV | 25 µV (max) | 60 µV | 50 µV |
| Supply Voltage Range | 5V to 36V | 5V to 36V | 4.5V to 36V | 4.5V to 36V |
| Price (1pc) | $5.29 | $6.50 | $4.50 | $3.80 |
Key Differentiators
- Lowest noise in its class (vs AD8221ARZ)
- Higher bandwidth (vs INA128)
- Higher slew rate (vs AD8221ARZ)
Design Notes
Ensure proper supply decoupling with 0.1 µF ceramic capacitors placed close to the +VS and -VS pins. For high-frequency noise, add a 10 µF tantalum capacitor in parallel. The AD8421 operates from 5V to 36V, so verify the supply voltage does not exceed the absolute maximum ratings. Use a low-noise supply to maintain the amplifier's low noise performance.
For optimal noise performance, keep the input traces short and shielded. Use a ground plane under the amplifier to reduce noise pickup. The gain-setting resistors (RG) should be placed close to the RG pins to minimize parasitic capacitance. For high-speed applications, use a 4-layer PCB with dedicated power and ground planes.
Do not exceed the input common-mode voltage range, as this can cause output saturation. The reference pin (REF) can be used to level-shift the output, but ensure it is driven by a low-impedance source. For single-supply operation, set the REF pin to mid-supply to maximize output swing. Also, avoid using high-value gain resistors, as they can increase noise and offset errors.
Compliance Information
RoHS compliant per Analog Devices product page. Not AEC-Q100 qualified. Lead-free per SOIC package.
