The AD645 is a low noise, precision FET input op amp. It offers the pico amp level input currents of a FET input device coupled with offset drift and input voltage noise comparable to a high performance bipolar input amplifier. The AD645 has been improved to offer the lowest offset drift in a FET op amp, 1 V/C. Offset voltage drift is measured and trimmed at wafer level for the lowest cost possible. An inherently low noise architecture and advanced manufacturing techniques result in a device with a guaranteed low input voltage noise of 2 V p-p, 0.1 Hz to 10 Hz. This level of dc performance along with low input currents make the AD645 an excellent choice for high impedance applications where stability is of prime concern.