Direct-coupled amplifier for the measurement of small currents

Abstract

Methods for the reduction of grid current noise and leakage currents in direct-coupled preamplifier circuits are discussed. It is shown that, by combining a cathode follower pream-plifier with a negative feedback output circuit, input grid resistors of very high value can be used. The construction and performance of an amplifier using these principles is described. Features of this circuit are a high zero stability and an adjustable time constant.