Autozero op amp improves sensor performance

The MAX44251 is a 20V, low noise dual op amp that the company says uses proprietary autozero technology. This is designed to enable continuous self calibration and ensure system accuracy over time, temperature and power supply variations. According to Maxim, the precision (<6µV initial offset) over the 2.7 to 20V operating range is 'unmatched' by competitive products, improving system accuracy and minimising errors during signal conditioning. The accuracy over the extended range makes the device suitable for applications such as rf immunity filters that remove unwanted rf signals often found in industrial and medical applications. It can also be used for high voltage applications that require ultra low noise and ultra high dc precision, such as interfacing with pressure sensors, strain gauges, precision weight scales and medical instrumentation. The low 1.15mA current consumption per channel offers 10MHz gain bandwidth and what Maxim says is the industry's lowest noise (5.9nV/vHz input referred voltage) for a high voltage autozero op amp. According to Maxim, the MAX44251 has near zero dc offset and drift through the use of a proprietary autocorrelating, zeroing technique. Autozeroing constantly measures and compensates the input offset, thus eliminating drift over time and temperature and the effect of 1/f noise. The low input offset voltage of 6µV (max) and voltage temperature drift of 19nV/°C (max) are said to offer precision across -40 to 125°C. Autozero offset calibration also eliminates the effects of power supply variation and even common mode variations. The device's power supply rejection ratio, common mode rejection ratio and large signal voltage gain exceed 135dB at 25°C, increasing its flexibility of the design and minimising errors during signal conditioning.