AD621:  Low Drift, Low Power Instrumentation Amp with fixed gains of 10 and 100

The AD621 is an easy to use, low cost, low power, high accuracy instrumentation amplifier which is ideally suited for a wide range of applications. Its unique combination of high performance, small size and low power, outperforms discrete in amp implementations. High functionality, low gain errors and low gain drift errors are achieved by the use of internal gain setting resistors. Fixed gains of 10 and 100 can be easily set via external pin strapping. The AD621 is fully specified as a total system, therefore, simplifying the design process.

For portable or remote applications, where power dissipation, size and weight are critical, the AD621 features a very low supply current of 1.3 mA max and is packaged in a compact 8-pin SOIC, 8-pin plastic DIP or 8-pin cerdip. The AD621 also excels in applications requiring high total accuracy, such as precision data acquisition systems used in weigh scales and transducer interface circuits. Low maximum error specifications including nonlinearity of 10 ppm, gain drift of 5 ppm°/C, 50 µV offset voltage and 0.6 mV/°C offset drift ("B" grade), make possible total system performance at a lower cost than has been previously achieved with discrete designs or with other monolithic instrumentation amplifiers.

When operating from high source impedances, as in ECG and blood pressure monitors, the AD621 features the ideal combination of low noise and low input bias currents. Voltage noise is specified as 9 nV/(root) Hz at 1 kHz and 0.28 µV p-p from 0.1 Hz to 10 Hz. Input current noise is also extremely low at 0.1 pA/Hz. The AD621 outperforms FET input devices with an input bias current specification of 1.5 nA max over the full industrial temperature range.