The AD8420 is a micropower, low-cost instrumentation amplifier designed for precision amplification of small differential signals in the presence of large common-mode voltages.

Function: Wide Supply Range, Micropower, Rail-to-Rail Instrumentation Amplifier

Package: 8-lead MSOP type

Manufacturer: Analog Devices

Pinouts:

Description

The AD8420 is a low cost, micropower, wide supply range, instrumentation amplifier with a rail-to-rail output and a novel architecture that allows for extremely flexible design. It is optimized to amplify small differential voltages in the presence of large common-mode signals. The AD8420 is based on an indirect current feedback architecturethat gives it an excellent input common-mode range. Unlike conventional instrumentation amplifiers, the AD8420can easily amplify signals at or even slightly below ground without requiring dual supplies. The AD8420 has rail-to-rail output, and the output voltage swing is completely independent of the input common mode voltage.

It utilizes an indirect current feedback architecture, enabling a wide input common-mode range and allowing operation even when input signals are at or slightly below ground on a single supply. With rail-to-rail output and very low power consumption, it is well suited for battery-powered and high-accuracy sensing applications.

Features

• Micropower operation with maximum supply current of 80µA
• High common-mode rejection ratio (CMRR ≥ 100 dB)
• Rail-to-rail output swing
• Wide input voltage range, including below ground capability
• Gain set using two external resistors
• Low gain drift across all gain settings
• Wide supply voltage range:
  • Single supply: 2.7V to 36V
  • Dual supply: ±2.7V to ±18V
• Bandwidth: 2.5 kHz at gain of 100
• Low input voltage noise: 55 nV/√Hz
• High DC precision with low offset voltage (max 125µV)
• Low offset drift (max 1µV/°C)
• Capable of driving capacitive loads up to ~700 pF

Design Notes

• Indirect current feedback architecture provides extended input common-mode range
• Can handle input signals near or below ground without requiring negative supply
• Gain is externally configurable, enabling flexible system design
• Low quiescent current makes it ideal for battery-powered applications
• Careful PCB layout is required to maintain high CMRR and low noise performance
• Capable of directly driving ADC inputs due to rail-to-rail output

How to Choose This Part

• Select for low-power precision measurement systems
• Ensure bandwidth meets application requirements at desired gain
• Evaluate noise performance for low-level signal amplification
• Confirm supply voltage compatibility with system design
• Consider alternative instrumentation amplifiers for higher bandwidth needs

Applications

• Bridge amplifiers
• Pressure measurement systems
• Medical instrumentation
• Portable data acquisition
• Multichannel sensing systems

Alternative / Equivalent Products

• AD623 – Low-cost instrumentation amplifier
• INA333 – Texas Instruments micropower INA
• AD8226 – Precision instrumentation amplifier
• INA126 – General-purpose instrumentation amplifier
• AD620 – Widely used instrumentation amplifier

Other data sheets are available within the file:

AD8420ARMZ, AD8420ARMZ-R7, AD8420ARMZ-RL

AD8420 Datasheet PDF Download