A Sub-Millimicroampere Current Amplifier Utilizing an Unusual Transistor Effect

Due to a very unusual-effect that occurred when certain transistors were operated at low current levels, a direct coupled, transistorized, current amplifier has been developed with sensitivity extending below the millimicroampere region of input currents. This amplifier was necessary for the measurement of certain characteristics of the experimental controlled fusion machine, DCX (Direct Current Experiment). Characteristics of the high-gain transistors are presented along with a description of the design and resulting characteristics of a current amplifier with sensitivities of l/10-8, 1/10-9, and 1/10-10 volt/amp. A possible explanation of the high-gain effect involving the existence of an N-type inversion layer on the P-type base of the silicon transistors of interest suggests the need for more basic experiments on the effects of inversion layers on transistor action.