311J

The models 310 and 311J are operational amplifiers with extremely low input bias currents and high input impedances. As such, they are applicable to a large number of electrometer amplifier applications which have traditionally been fulfilled (not without difficulty) by vacuum electrometer tubes. These specialized requirements are characterized by extremely high source impedances or where infinitesimal currents must be measured or amplified. Because of varactor bridge inputs, the all solid state 310 and 311J amplifiers are ideally suited to this type of requirement. Voltage drifts are small, noise is minimized, and the cost is low. In principles the operation of varactor bridge amplifiers is similar to that of vibrating reed electrometers
(parametric), but also includes the inherent advantages of solid state design.