Wideband (500 MHz) 16 bit dynamic range current mode input stage for photodetector readout

A low noise wideband current mode circuit with 16 bit dynamic range (DR) is presented. It has been designed as input stage of a transimpedance preamplifier for the readout of the cameras of the Cherenkov Telescope Array (CTA) project. A novel current division scheme at the very front end part of circuit is used to split the input current in two or more scaled output currents which are connected to independent current mirrors. The mirror of the high gain path comprises a dedicated saturation control circuit needed to assure an accurate current division. Two ASIC prototypes have been designed in AMS SiGe BiCMOS 0.35um technology. Measurement results are presented: BW of 500 MHz, DR of 16 bits, input referred ENC below 4000 electrons and relative linearity error below 2%. The current mode circuit can be operated at 3.3 V and lower, with low power consumption (<;10 mW).