Precision op amps target instrumentation, DAQ apps

A pair of instrumentation amplifiers from Analog Devices Inc. shows that precise, high-performance analog functions still play a critical role in instrumentation and DAQ applications. Such in-amps provide signal conditioning and amplification over large input voltage ranges, with well-defined DC accuracy and gain settings.

The AD8250, with digitally (or pin-strapped) settable gains of 1, 2, 5 and 10, and the similar AD8251 with gains of 1, 2, 4 and 8, operate on signals up to ±10V range, with a 12MHz 3dB bandwidth (at gain of 1), to accommodate fast-slewing signals. Common-mode rejection ratio is at least 80dB to 10kHz, also at unity gain, and 100dB at gain of 10. The 30V/μs slew rate, and 0.5μs settling time to 0.01 percent, illustrate AC performance.

But a good in-amp is also defined by its DC specs. These devices promise input-referred noise below 15nV per √Hz at gain of 10, gain drift better than 10ppm/°C, input offset below 100μV, coupled with maximum input offset drift of 1μV/°C.

The in-amps operate from ±5- to ±12V supplies, and consume less than 4mA. Housed in 10-lead MSOP packages (3.1-by-3.1mm dimensions), which the vendor claims is 90 percent smaller than competitive 16-lead SOIC devices, the in-amps are priced at $4.95 each for 1,000-unit quantities.

- Bill Schweber
Planet Analog