Small Current Measurements with Insulated Gate Field Effect Transistor Electrometers

Put FETs to Work in Electrometers

Field-effect transistors, with their high impedance and low noise, can effectively measure very low currents. To bring the FET up to electrometer standards (so that it can measure currents of, say, 10 (sup -13) amp) the designer must know where the noise is and what to do about it.