The OPA111 is a precision monolithic dielectrically isolated FET (Difet ®) operational amplifier. Outstanding performance characteristics allow its use in the most critical instrumentation applications. Noise, bias current, voltage offset, drift, open-loop gain, common-mode rejection, and power supply rejection are superior to BIFET® amplifiers. Very low bias current is obtained by dielectric isolation with on-chip guarding. Laser trimming of thin-film resistors gives very low offset and drift. Extremely low noise is achieved with patented circuit design techniques. A new cascode design allows high precision input specifications and reduced susceptibility to flicker noise. Standard 741 pin configuration allows upgrading of existing designs to higher performance levels.