The AD743 is an ultralow noise, precision, FET input, monolithic operational amplifier. It offers a combination of the ultralow voltage noise generally associated with bipolar input op amps and the very low input current of a FET input device. Furthermore, the AD743 does not exhibit an output phase reversal when the negative common-mode voltage limit is exceeded. The AD743's guaranteed, maximum input voltage noise of 4.0 nV/Hz at 10 kHz is unsurpassed for a FET input monolithic op amp, as is the maximum 1.0 V p-p, 0.1 Hz to 10 Hz noise. The AD743 also has excellent dc performance with 250 pA maximum input bias current and 0.5 mV maximum offset voltage. The AD743 is specifically designed for use as a preamp in capacitive sensors, such as ceramic hydrophones. The AD743J is rated over the commercial temperature range of 0C to 70C. The AD743 is available in a 16-lead SOIC and 8-lead PDIP.