GENERAL DESCRIPTION
The AD8244 is a precision, low power, FET input, quad unity-gain buffer that is designed to isolate very large source impedances from the rest of the signal chain. The 2 pA maximum bias current, near zero current noise, and 10 TΩ input impedance introduce almost no error, even with source impedance well into the megaohms.

FEATURES
Low power
  250 µA maximum supply current per amplifier
FET input
  2 pA maximum input bias current at 25°C
  Extremely high input impedance
Low noise
  13 nV/√Hz voltage noise at 1 kHz
  0.4 µV p-p voltage noise (0.1 Hz to 10 Hz)
  0.8 fA/√Hz current noise at 1 kHz
High dc precision
  3 µV/°C maximum offset drift (B grade)
3 MHz bandwidth
Unique pinout
  No leakage from inputs to supply pins
  Provides guarding capability
Rail-to-rail output
Single-supply operation
  Input range extends to ground
Wide supply range
  Single-supply: 3 V to 36 V
  Dual-supply: ±1.5 V to ±18 V
Available in a compact 10-lead MSOP

APPLICATIONS
Biopotential electrodes
Medical instrumentation
High impedance sensor conditioning
Filters
Photodiode amplifiers