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
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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