AD8421 Datasheet

• Low power
  • 2.3 mA maximum supply current
• Low noise
  • 3.2 nV/√Hz maximum input voltage noise at 1 kHz
  • 200 fA/√Hz current noise at 1 kHz
• Excellent ac specifications 
  • 10 MHz bandwidth (G = 1)
  • 2 MHz bandwidth (G = 100)
  • 0.6 µs settling time to 0.001% (G = 10)
  • 80 dB CMRR to 20 kHz (G = 1)
  • 35 V/µs slew rate
• High precision dc performance (AD8421BRZ)
  • 94 dB CMRR minimum (G = 1)
  • 0.2 μV/°C maximum input offset voltage drift
  • 1 ppm/°C maximum gain drift (G = 1)
• 500 pA maximum input bias current
• Inputs protected to 40 V from opposite supply
• ±2.5 V to ±18 V dual supply (5 V to 36 V single supply)
• Gain set with a single resistor (G = 1 to 10,000)
• Available in 8-lead LFCSP, 8-lead MSOP, and 8-lead SOIC
• Available As Known Good Die and fully guaranteed to data sheet specifications

• Medical instrumentation
• Precision data acquisition
• Microphone preamplification
• Vibration analysis
• Multiplexed input applications
• ADC driver

The AD8421 is a low cost, low power, extremely low noise, ultralow bias current, high speed instrumentation amplifier that is ideally suited for a broad spectrum of signal conditioning and data acquisition applications. This product features extremely high CMRR, allowing it to extract low level signals in the presence of high frequency common-mode noise over a wide temperature range.

The 10 MHz bandwidth, 35 V/µs slew rate, and 0.6 µs settling time to 0.001% (G = 10) allow the AD8421 to amplify high speed signals and excel in applications that require high channel count, multiplexed systems. Even at higher gains, the current feedback architecture maintains high performance; for example, at G = 100, the bandwidth is 2 MHz and the settling time is 0.8 µs. The AD8421 has excellent distortion performance, making it suitable for use in demanding applications such as vibration analysis.

The AD8421 delivers industry-leading 3 nV/√Hz input voltage noise and 200 fA/√Hz current noise with only 2 mA quiescent current, making it an ideal choice for measuring low level signals. For applications with high source impedance, the AD8421 employs innovative process technology and design techniques to provide noise performance that is limited only by the sensor.

The AD8421 uses unique protection methods to ensure robust inputs while still maintaining very low noise. This protection allows input voltages up to 40 V from the opposite supply rail without damage to the part.

A single resistor sets gains between 1 and 10,000. The reference pin can be used to apply a precise offset to the output voltage.

The AD8421 performance is specified from −40°C to +85°C for the 8-lead MSOP and SOIC packages, and from −40°C to 125°C for the 8-lead LFCSP package.