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Analog Devices Inc. AD8421ARMZ
- Part No.:
- AD8421ARMZ
- Manufacturer:
- Analog Devices Inc.
- Category:
- Instrumentation, Op Amps, Buffer Amps
- Package:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Datasheet:
-
AD8421ARMZ.pdf
- Description:
- IC INST AMP 1 CIRCUIT 8MSOP
- Quantity:
- Payment:
- Shipping:
Inventory:513
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Product details
Overview
AD8421ARMZ from Analog Devices is a low-power, ultralow-noise instrumentation amplifier optimized for precision signal conditioning in high-impedance sensor interfaces. It delivers 3.2 nV/√Hz input voltage noise, 200 fA/√Hz current noise, 2.3 mA supply current, and 10 MHz bandwidth at G = 1 - enabling accurate amplification of microvolt-level biomedical and vibration signals in battery-powered or thermally constrained systems.
For engineers reviewing the AD8421ARMZ datasheet, AD8421ARMZ pinout, AD8421ARMZ application, or AD8421ARMZ equivalent, this page provides verified specifications, package-specific thermal data, gain-setting resistor design guidance, CMRR vs. frequency behavior, and validated alternative options for medical instrumentation, ADC driver, and multiplexed data acquisition use cases.
Technical Context
The AD8421ARMZ employs a current-feedback architecture that maintains 2 MHz bandwidth and 0.8 µs settling to 0.001% at G = 100 - unlike conventional voltage-feedback in-amps. Its input stage uses guarded JFET inputs with 30 GΩ differential impedance and integrated ±40 V overvoltage protection relative to opposite supply rail.
Gain is set by a single external resistor (RG) across Pins 2–3 per G = 1 + 9.9 kΩ/RG, supporting 1–10,000× range. The REF pin enables precise output offset control with 1 ppm/V reference gain accuracy and 20 kΩ input resistance, critical for ratiometric sensor interfacing.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Noise | 3.2 nV/√Hz at 1 kHz - enables resolution of sub-µV signals from high-Z sources like piezoelectric sensors. |
| Supply Current | 2.3 mA max - supports portable, multi-channel DAQ systems with thermal budget ≤150 mW per channel. |
| CMRR | 92 dB min at DC (ARM grade), 80 dB at 20 kHz - rejects EMI-coupled common-mode interference in industrial environments. |
| Bandwidth | 10 MHz at G = 1, 2 MHz at G = 100 - preserves transient fidelity in vibration analysis up to 100 kHz. |
| Input Impedance | 30 GΩ || 3 pF differential - minimizes loading error on MEMS accelerometers and strain gauges. |
| Gain Range | 1 to 10,000 via single RG resistor - simplifies calibration and eliminates trim potentiometers in production test fixtures. |
| Operating Temp | −40°C to +85°C (specified), −40°C to +125°C (operational) - suitable for automotive under-hood sensor signal chains. |
Pinout & Package
AD8421ARMZ is packaged in an 8-lead MSOP (RM package), with θJA = 138.6°C/W on a 4-layer JEDEC PCB. Exposed pad must be connected to −VS or left floating per datasheet Figure 3.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (−IN) | Negative input terminal | Differential input node; accepts voltages from −VS + 2.3 V to +VS − 1.8 V with ±40 V fault tolerance. |
| 2, 3 (RG) | Gain-setting terminals | Resistor connection points defining G = 1 + 9.9 kΩ/RG; 0.1% tolerance RG yields <0.2% gain error at G = 100. |
| 4 (+IN) | Positive input terminal | Differential input node; matched to −IN for >92 dB CMRR; same voltage range and protection as −IN. |
| 5 (−VS) | Negative power supply | Accepts −2.5 V to −18 V; exposed pad connection point for thermal management and noise reduction. |
| 6 (REF) | Reference voltage input | Drives output offset with 1 ppm/V gain accuracy; 20 kΩ input resistance avoids loading precision voltage references. |
| 7 (VOUT) | Amplified output | Delivers rail-to-rail swing (−VS + 1.2 V to +VS − 1.6 V) into 2 kΩ load; short-circuit protected to ±65 mA. |
| 8 (+VS) | Positive power supply | Accepts +2.5 V to +18 V; supplies internal bias networks and output stage; decoupling required within 1 cm. |
Key Features
| Feature | Design Value |
|---|---|
| Ultralow input current noise | 200 fA/√Hz at 1 kHz - preserves SNR when amplifying signals from >1 MΩ source impedances. |
| Integrated input overvoltage protection | Withstands ±40 V beyond opposite supply rail without latch-up or parametric shift - eliminates external clamping diodes. |
| Single-resistor programmable gain | G = 1 to 10,000 via RG; no external op amps or feedback networks needed - reduces BOM count and layout area. |
| High-speed settling | 0.6 µs to 0.001% at G = 10 - enables >1 MSPS multiplexed sampling in 16-bit data acquisition systems. |
| Wide supply range | ±2.5 V to ±18 V dual or 5 V to 36 V single supply - interoperable with legacy industrial rails and modern low-voltage MCUs. |
Applications
| Medical Instrumentation | Precision Data Acquisition |
|---|---|
Use Scenario: Amplifying ECG electrode signals with 50/60 Hz common-mode interference and <10 µV differential amplitude. IC Role / Device Role / Timing Role: Front-end instrumentation amplifier providing 92 dB CMRR and 3.2 nV/√Hz noise floor before 24-bit sigma-delta ADC. Use Value: Enables detection of P-wave morphology changes without analog filtering, reducing system latency by 300 µs vs. cascaded op-amp solutions. | Use Scenario: Conditioning outputs from 32-channel thermocouple array with cold-junction compensation. IC Role / Device Role / Timing Role: Channel-selectable in-amp with REF pin tied to precision DAC for per-channel offset correction. Use Value: Achieves 0.1°C measurement accuracy across −40°C to +125°C using single-point calibration, eliminating per-channel trim components. |
| Vibration Analysis | ADC Driver |
Use Scenario: Signal conditioning for piezoelectric accelerometers in predictive maintenance sensors monitoring bearing faults at 2–10 kHz. IC Role / Device Role / Timing Role: High-bandwidth (2 MHz @ G = 100), low-distortion amplifier driving anti-alias filter into SAR ADC. Use Value: Preserves 5th harmonic content of impact transients, enabling early-stage fault detection via time-domain envelope analysis. | Use Scenario: Driving AD7685 16-bit SAR ADC input with 10 V full-scale range and 1 µs conversion time. IC Role / Device Role / Timing Role: Low-output-impedance buffer with 35 V/µs slew rate and 0.6 µs settling to 0.001%. Use Value: Prevents code-dependent missing codes during 1 MSPS sampling, maintaining ENOB ≥15.2 bits across full dynamic range. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar instrumentation amplifier applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AD8420ARMZ | Higher 12 nV/√Hz noise, 1.5 mA supply current, 1.5 MHz BW at G = 100, no REF pin. | Limited to lower-resolution (<14-bit) systems where offset trimming is handled externally. | Select when cost sensitivity outweighs noise performance and REF functionality is unnecessary. |
| INA128UA | 12 nV/√Hz noise, 1.5 mA supply current, 1.3 MHz BW at G = 100, fixed gain options require external resistors. | Suitable for non-multiplexed, single-channel industrial transmitters with relaxed settling requirements. | Choose for legacy designs requiring SOIC-8 footprint compatibility and TI-supplied evaluation boards. |
Compared with AD8420ARMZ and INA128UA, AD8421ARMZ provides 4× lower input voltage noise and integrated REF functionality - delivering higher effective resolution in battery-powered, multi-channel, or high-frequency vibration sensing applications without added external components.
Availability
AD8421ARMZ is available at Aetrix Electronics and suitable for medical instrumentation, precision data acquisition, and vibration analysis requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for AD8421ARMZ includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Analog Devices is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets since 1965.
The AD8421 belongs to Analog Devices' precision instrumentation amplifier product line, engineered specifically for extracting low-amplitude, high-impedance sensor signals in electrically noisy, thermally variable, and power-constrained environments.
FAQ
What is the maximum gain achievable with AD8421ARMZ?
The AD8421ARMZ supports a gain range of 1 to 10,000, set by a single external resistor (RG) connected between Pins 2 and 3 using the formula G = 1 + 9.9 kΩ/RG. At G = 10,000, RG = 0.99 Ω - requiring a precision, low-inductance resistor and careful PCB layout to maintain stability and noise performance. The AD8421ARMZ maintains usable bandwidth (>200 kHz) and CMRR (>110 dB) even at G = 1000.
Does AD8421ARMZ require external protection diodes on its inputs?
No, AD8421ARMZ does not require external protection diodes. Its inputs are internally protected to ±40 V beyond the opposite supply rail (e.g., +IN can tolerate −VS − 40 V or +VS + 40 V), as confirmed in Absolute Maximum Ratings Table 4. This robustness eliminates external clamping components in most industrial and medical sensor front-ends, reducing board space and failure modes.
How does the REF pin function in AD8421ARMZ?
The REF pin on AD8421ARMZ provides a high-impedance (20 kΩ), low-gain-error (±0.01%) path to inject a precise DC offset onto the output. When driven by a low-noise voltage source (e.g., ADR435), it shifts VOUT by (VREF × 1) independent of gain setting. This enables ratiometric sensor interfacing, level-shifting for unipolar ADCs, or active baseline correction - all without affecting input common-mode range or CMRR.
What is the thermal performance difference between AD8421ARMZ and AD8421BRZ packages?
AD8421ARMZ (8-lead MSOP) has θJA = 138.6°C/W, while AD8421BRZ (8-lead SOIC) has θJA = 107.8°C/W - a 29% higher junction-to-ambient thermal resistance. In a 2.3 mA, ±15 V application dissipating ~70 mW, AD8421ARMZ will run ~22°C hotter than AD8421BRZ under identical PCB conditions. For high-density layouts or ambient temperatures >70°C, derating or enhanced copper pour is recommended for AD8421ARMZ.
Can AD8421ARMZ operate from a single 5 V supply?
Yes, AD8421ARMZ supports single-supply operation from 5 V to 36 V. With +VS = 5 V and −VS = 0 V, its input common-mode range extends from 2.3 V to 3.2 V (−VS + 2.3 V to +VS − 1.8 V), and output swings from 1.2 V to 3.4 V. For rail-to-rail input/output capability in single-supply systems, the REF pin must be biased to mid-supply (e.g., 2.5 V) to center the output dynamic range - a configuration validated in Figure 12 of the AD8421ARMZ datasheet.
AD8421ARMZ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Amplifier Type:
- Instrumentation
- Number of Circuits:
- 1
- Output Type:
- -
- Slew Rate:
- 35V/µs
- Gain Bandwidth Product:
- -
- -3db Bandwidth:
- 10 MHz
- Current - Input Bias:
- 1 nA
- Voltage - Input Offset:
- 60 µV
- Current - Supply:
- 2mA
- Current - Output / Channel:
- 65 mA
- Voltage - Supply Span (Min):
- 5 V
- Voltage - Supply Span (Max):
- 36 V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-MSOP
AD8421ARMZ FAQ
1.How can I place an order for AD8421ARMZ through Aetrix?
Please submit a Request for Quotation (RFQ) for AD8421ARMZ on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for AD8421ARMZ reliable?
The price and inventory of AD8421ARMZ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AD8421ARMZ is usually 5 days.
3.What payment methods are accepted for AD8421ARMZ?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AD8421ARMZ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AD8421ARMZ?
AD8421ARMZ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AD8421ARMZ order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for AD8421ARMZ?
For technical support, including AD8421ARMZ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AD8421ARMZ requirements.
6.How does Aetrix verify that AD8421ARMZ is sourced from the original manufacturer or authorized distributors?
All AD8421ARMZ products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that AD8421ARMZ meets industry standards.
7.What is the process for return or replacement of AD8421ARMZ?
All AD8421ARMZ units undergo pre-shipment inspection (PSI). If there is an issue with AD8421ARMZ, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The AD8421ARMZ part is unused and in its original packaging.
Return procedure for AD8421ARMZ:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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