The AD549 is a low-input bias current monolithic electrometer operational amplifier. For accurate performance, input offset voltage and input offset voltage drift are laser trimmed. TopgateTM JFET technology, a process development only used by Analog Devices, Inc., is used to achieve the part's ultralow input current. This approach enables the manufacturing of JFETs with extremely low input currents that are compatible with a standard connection isolated bipolar process. The bootstrapped input stage's 1015 common-mode impedance ensures that the input current is entirely independent of the common mode voltage. The AD549 is ideal for applications that require very low input current and very low input offset voltage. It performs admirably as a preamp for a wide range of current output transducers, including photodiodes, photomultiplier tubes, and oxygen sensors. The AD549 can also be utilized as a precision integrator or a sample-and-hold with low droop. The AD549 is pin compatible with ordinary FET and electrometer op amps, enabling designers to improve the performance of existing systems at a cheap cost. The AD549 is supplied in a hermetic TO-99 package. Because the metal casing is linked to Pin 8, it can be independently connected to a point at the same voltage as the input terminals, eliminating stray leakage to the case. The AD549 is offered in four different performance levels. The J, K, and L models are rated for commercial temperatures ranging from 0°C to 70°C. The S grade is specified for military temperatures ranging from 55°C to 125°C and is available in MIL-STD-883B, Rev. C processing. Screening and extended reliability are other options. In addition, screening comprises a 168-hour burn-in period as well as various environmental and physical testing based on MIL-STD-883B, Rev. C.