LOW-TEMPERATURE COMPATIBLE IV CONVERTER

A novel design of a current-to-voltage (I-V) converter is described that shows a superior bandwidth and signal-to-noise ratio. It solves the problem of the nonuniform transfer function in the feedback loop of I-V converters with measuring resistors larger than 1 G-OMEGA. The input stage including four junction field effect transistors (FET) and the linearized measuring resistor have been integrated into a single TO-8 housing. Since junction FET's are not dependent on minority carriers, they can be operated at variable temperature with no degradation of performance, The signal-to-noise ratio is improved when the preamplifier can be cooled down to liquid nitrogen temperature or lower. The preamplifier needs five connections to the main stage, one of which is the signal ground. Even with a large separation between the preamplifier and the main stage, the bandwidth exceeds 1 MHz.