AD8420ARMZ - Micropower Rail-to-Rail In-Amp | Analog Devices
MPN: AD8420ARMZ ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.45 | $3.45 |
| 10 | $3.08 | $30.80 |
| 100 | $2.74 | $274.00 |
| 500 | $2.34 | $1,170.00 |
| 1,000 | $1.99 | $1,990.00 |
| 2,500 | $1.65 | $4,125.00 |
AD8420ARMZ Overview
An instrumentation amplifier (INA) is a precision differential amplifier with high common-mode rejection ratio (CMRR), high input impedance, and user-settable gain - typically realized through one gain-setting resistor. INAs are specialized building blocks in the analog signal chain, sitting between a sensor (bridge, thermocouple, biopotential electrode) and an analog-to-digital converter. They belong to the broader amplifier-IC family and are widely used where small signals must be extracted in the presence of large common-mode noise or DC offsets.
Key features of the AD8420ARMZ include 100 dB minimum DC CMRR (G = 100), a maximum input offset voltage of 250 µV, 30 nV/√Hz input voltage noise density, and ±18 V dual supply operation. The rail-to-rail output swing maximizes dynamic range when operating from low supply voltages, while the novel architecture eliminates the need for level shifting in single-supply designs. A single external resistor sets the gain from 1 to 1000, simplifying BOM and layout.
Typical applications for the AD8420ARMZ include battery-powered sensor signal conditioning, ECG/biomedical front ends, industrial process-control transducers (pressure, strain gauge, load cell), and thermocouple/RTD amplifiers. The wide supply range and 90 µA quiescent current make it suitable for portable instrumentation, while ±18 V capability addresses industrial instrumentation.
When designing with this part, place the gain-setting resistor close to the RG pin to minimize parasitic effects, use 0.1 µF decoupling capacitors at the supply pins, and follow proper PCB layout for high-CMRR performance (matched input traces, guard ring around inputs). For new designs consider the AD8421ARMZ (higher precision) or AD8237ARMZ (zero-drift) if your application demands tighter offset or lower noise.
Drop-in alternatives for AD8420ARMZ — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with AD8420ARMZ (same form factor and footprint) — differing in Gain Range, Input Common-Mode Range, Input Offset Voltage (max), Input Voltage Noise Density, Operating Temperature Range.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
AD8420ARMZ-R7
✅ Drop-In📋 Reference alternative (not in catalog)
AD8420ARMZ-RL
✅ Drop-In📋 Reference alternative (not in catalog)
AD8421ARMZ
✅ Drop-In📋 Reference alternative (not in catalog)
AD8237ARMZ
✅ Drop-In✓ In Stock
$1.45 / Unit
View Datasheet →AD8420ARMZ Maximum Ratings & Electrical Characteristics
| Product Type | Instrumentation Amplifier |
| Number of Channels | 1 |
| Package | 8-MSOP (RM-8) |
| Supply Voltage Range (Single) | 2.7 V to 36 V |
| Supply Voltage Range (Dual) | ±2.5 V to ±18 V |
| Quiescent Current (typical) | 90 µA |
| Bandwidth (-3 dB, G=1) | 6 MHz |
| Input Offset Voltage (max) | 250 µV |
| Input Voltage Noise Density | 30 nV/√Hz |
| CMRR (DC, G=100) | 100 dB minimum |
| Gain Range | 1 to 1000 (set by single external resistor) |
| Output Type | Rail-to-Rail |
| Slew Rate | 1 V/µs (typical) |
| Operating Temperature Range | -40 °C to +85 °C |
| Input Common-Mode Range | Includes ground; below ground on single supply |
| Mounting Type | Surface Mount |
| MSL Level | 1 (Unlimited) |
| RoHS Compliance | RoHS3 Compliant |
| REACH Status | REACH Unaffected |
| Lead-Free | Yes |
AD8420ARMZ Pin Configuration
| Pin 1 | RG — Gain-setting resistor pin (RG between pins 1 and 8) |
| Pin 2 | -IN — Inverting input |
| Pin 3 | +IN — Noninverting input |
| Pin 4 | VS- — Negative supply (or ground for single supply) |
| Pin 5 | REF — Reference input (sets output mid-scale; typically tied to mid-supply or ground) |
| Pin 6 | OUT — Amplifier output (rail-to-rail) |
| Pin 7 | VS+ — Positive supply |
| Pin 8 | RG — Gain-setting resistor pin (RG between pins 1 and 8) |
Typical Applications
AD8420ARMZ is suitable for 6 applications: Battery-Powered Sensor Signal Conditioning, ECG and Biopotential Front End, Industrial Process-Control Transducers, Thermocouple and RTD Amplification, Portable Instrumentation and Handheld Meters, Current-Sense and Shunt Amplifiers.
Battery-Powered Sensor Signal Conditioning
The AD8420ARMZ is well-suited to battery-powered sensor front ends because of its 90 µA typical quiescent current and wide single-supply range of 2.7 V to 36 V. In a portable pressure or strain-gauge system, it sits between a bridge sensor and an ADC, where its 100 dB minimum DC CMRR (G = 100) rejects common-mode DC and 50/60 Hz interference on the bridge output. The rail-to-rail output maximizes dynamic range on 3.3 V or 5 V rails, and the 6 MHz bandwidth at G = 1 supports signal rates well beyond typical sensor bandwidths. Single-resistor gain setting (G = 1 + 19.8 kΩ / RG) minimizes BOM cost.
Recommended
ECG and Biopotential Front End
In ECG and other biopotential applications, the AD8420ARMZ amplifies small differential electrode voltages (typically 0.5 mV to 5 mV) in the presence of large DC common-mode voltages (often ±300 mV or more from skin-electrode half-cell potentials). Its indirect current-feedback architecture amplifies signals at or below ground without dual supplies - a critical requirement for single-supply ECG designs where one electrode is near ground. The 100 dB minimum DC CMRR and 30 nV/√Hz input noise density support diagnostic-grade signal-to-noise. Pair with right-leg-drive feedback for best common-mode rejection.
Recommended
Industrial Process-Control Transducers
The AD8420ARMZ is widely used in industrial process-control transducer signal chains for pressure, strain-gauge, load-cell, and flow sensors. Its ±18 V dual-supply capability handles industrial ±15 V rails and provides extra headroom for high common-mode bridge excitation. The 100 dB minimum CMRR at high gain rejects ground-loop and 50/60 Hz line-frequency noise in plant-floor environments. The wide operating temperature range of -40 °C to +85 °C supports most industrial cabinets and field enclosures, while the MSOP-8 footprint enables compact, densely populated multi-channel PLC and DAQ modules.
Recommended
Thermocouple and RTD Amplification
For thermocouple (J, K, T, E types) and RTD (PT100/PT1000) amplification, the AD8420ARMZ's high gain (up to 1000) and excellent DC CMRR extract microvolt-level thermoelectric voltages from millivolt-scale common-mode sensor bias. The wide-supply range accommodates 5 V excitation for the RTD bridge plus amplifier on a single rail, while the 250 µV maximum input offset is acceptable for non-thermocouple-junction applications where cold-junction compensation is performed in software or a dedicated temperature sensor. For Type T/K thermocouples requiring tighter offset, consider the AD8421ARMZ.
Recommended
Portable Instrumentation and Handheld Meters
Battery-powered handheld multimeters, data loggers, and field instrumentation benefit from the AD8420ARMZ's 90 µA quiescent current and wide 2.7 V to 36 V supply range - directly accepting Li-ion, 9 V, and 12 V battery stacks. The rail-to-rail output swing maximizes dynamic range on 3.3 V ADC rails, while the 6 MHz bandwidth supports both DC measurement channels and modest-bandwidth AC signal chains. The MSOP-8 footprint keeps the analog front end under 9 mm² per channel, allowing 4- and 16-channel multi-function instruments to fit in compact handheld enclosures without sacrificing battery life.
Recommended
Current-Sense and Shunt Amplifiers
While traditionally a dedicated current-sense amplifier, the AD8420ARMZ also serves well as a high-side or low-side shunt current amplifier in power-management and battery-monitoring circuits. With a small shunt resistor (10 mΩ to 100 mΩ) and G = 100, it amplifies currents from 10 mA to 10 A into a 0 V to 5 V output range suitable for an ADC. Its wide common-mode input range - extending below ground on single supply - accommodates low-side shunts without requiring dual supplies. The 90 µA Iq adds minimal load to the monitored rail.
Recommended
Recommended Products Summary
Engineering reference data for AD8420ARMZ — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | AD8420ARMZ-R7 | AD8420ARMZ-RL | AD8421ARMZ | AD8237ARMZ |
|---|---|---|---|---|---|
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| Package | 8-MSOP (RM-8) | 8-MSOP (RM-8) - same | 8-MSOP (RM-8) - same | 8-MSOP (RM-8) - same | 8-MSOP (RM-8) - same |
| Input Offset Voltage (max) | 250 µV | 250 µV | 250 µV | 25 µV | 15 µV |
| Bandwidth (-3 dB, G=1) | 6 MHz | 6 MHz | 6 MHz | ~10 MHz | ~30 kHz |
| Supply Voltage Range (Single) | 2.7 V to 36 V | 2.7 V to 36 V | 2.7 V to 36 V | ~±2.5 V to ±18 V dual | 1.8 V to 5.5 V |
| Output Type | Rail-to-Rail | Rail-to-Rail | Rail-to-Rail | Rail-to-Rail | Rail-to-Rail |
| Pinout Compatibility | Reference | Identical pinout | Identical pinout | Same MSOP-8, verify gain pin config | Same MSOP-8, verify gain pin config |
Key Differentiators
- Lowest quiescent current in its bandwidth class (vs AD8421ARMZ)
- Wide supply range up to 36 V single / ±18 V dual (vs AD8237ARMZ)
- Below-ground input common-mode on single supply (vs Conventional 3-op-amp INAs)
- Single-resistor gain setting from 1 to 1000 (vs AD8421ARMZ)
Design Notes
Place the gain-setting resistor RG as close as possible to pins 1 and 8 to minimize parasitic capacitance. Use 0.1 µF decoupling capacitors on each supply pin (VS+ and VS-), placed within 2 mm of the IC. Keep input traces matched and short - the AD8420 datasheet recommends a guard ring tied to REF potential around the input traces to maximize CMRR, especially in high-impedance bridge applications.
Do not use a standard 1 % RG resistor if gain accuracy is critical - the gain error of the AD8420 directly adds the RG tolerance to the gain formula. For best CMRR, the REF pin should be driven by a low-impedance source (op-amp buffer or mid-supply rail), not left floating or driven by a resistor divider. Also note that the quiescent current spec of 90 µA is typical - worst-case may approach ~5 mA during transient conditions.
The MSOP-8 package has a thermal resistance (θJA) of approximately 150 °C/W. At maximum supply (36 V single, 18 V dual) and full output swing, internal dissipation can reach ~50 mW, resulting in ~7.5 °C junction rise - well within the 85 °C operating limit. For high-gain high-output-voltage applications in elevated-temperature environments, verify junction temperature with the latest AD8420 datasheet derating curves.
Input common-mode range extends below ground on single supply, but at high source impedance or high frequency, the indirect current-feedback architecture's input capacitance (~5 pF) can interact with source resistance to create a parasitic zero in the transfer function. Keep source impedances below 10 kΩ for best high-frequency CMRR, or add a buffer amp (e.g., AD8627ARMZ or similar) for higher-impedance sources.
Compliance Information
RoHS3 compliant and REACH unaffected per PartGenie compliance records. Not AEC-Q100 qualified - this part targets industrial/medical/consumer applications, not automotive. Halogen-free status and conflict-minerals declaration should be confirmed with the manufacturer for specific lot requirements.
