Linear Seven-Decade Current/Voltage-to-Frequency Converter

A current-to-frequency converter was developed for low level current measurements of wide dynamic range. It measures currents from 5 ?? 10-13 to 6 ?? 10-5 amperes without range switching and by the use of state-of-the-art circuit components. It has a corresponding linear seven-decade transfer characteristic of 10-11 amperes per Hertz with a maximum output frequency of greater than 5 ?? 106 Hz. The converter was designed to monitor photomultiplier tube current in an automated thermoluminescent dosimetry (TLD) system.