Two AA cell instrumentation amplifier for body networks




The AD8237 is a micropower, zero drift, rail-to-rail input and output instrumentation amplifier. The relative match of two resistors sets any gain from 1 to 1000. The AD8237 has excellent gain accuracy performance that can be preserved at any gain with two ratio-matched resistors.

The AD8237 employs the indirect current feedback architecture to achieve a true rail-to-rail capability. Unlike conventional in-amps, the AD8237 can fully amplify signals with common-mode voltage at or even slightly beyond its supplies. This enables applications with high common-mode voltages to use smaller supplies and save power.

The AD8237 is an excellent choice for portable systems. With a minimum supply voltage of 1.8 V, a 115 μA typical supply current, and wide input range, the AD8237 makes full use of a limited power budget, yet offers bandwidth and drift performance suitable for bench-top systems.

FEATURES and BENEFITS

  •  Gain set with 2 external resistors
  •     — Can achieve low gain drift at all gains
  •     Ideal for battery powered instruments
  •     — Supply current: 115 μA
  •     — Rail-to-rail input and output
  •     — Zero input crossover distortion
  •     Designed for excellent dc performance
  •     — Minimum CMRR: 106 dB
  •     — Maximum offset voltage drift: 0.3 μV/°C
  •     — See data sheet for additional features
  •     Bandwidth mode pin (BW) to adjust compensation
  •     8 kV HBM ESD rating
  •     RFI filter on-chip
  •     Single-supply operation:
  •     1.8 V to 5.5 V
  •     8-lead MSOP package

Two AA cell instrumentation amplifier for body networksTwo AA cell instrumentation amplifier for body networks




Analog Devices has introduced a micro-power ‘zero-drift’ instrumentation amplifier whose inputs extend 300mV beyond the supply rails.

Dubbed AD8237, input offset drift is under 0.3µV/ºC, maximum gain error is 0.005%, drift is 0.5ppm/°C, and CMRR (common-mode rejection ratio) is 114dB.

“With a quiescent supply current of just over 100µA, the amplifier is suited for signal conditioning bridge, temperature and other similar sensors used in low-power designs,” said ADI. Target applications include battery-powered healthcare, consumer and precision instrumentation equipment such as infusion pumps, blood pressure monitors, 4-20mA sensors, gaming peripherals and consumer weigh scales.”

A single supply of 1.8-5.5V powers the chip and it comes in a MSOP-8 package.

Gain between 1 and 1,000 is set by the ratio of two external resistors.

 

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