Low Noise Front End ASIC With Current Mode Active Cooled Termination for the Upgrade of the LHCb Calorimeter

The current mode line terminating input stage of an integrated circuit for the upgrade of the LHCb calorimeter front end electronics is presented. The circuit is based on a current mode input stage followed by two fully differential interleaved channels, namely a switched integrator and a track and hold. The input stage employs a novel electronically cooled input termination scheme to achieve stringent noise requirements. Compared to previous designs, its novelty relies in the use of two current feedback loops to decrease and control the input impedance of a common base stage. Two prototypes in Austriamicrosystems SiGe BiCMOS 0.35 μm technology have been designed and tested. Key measurements have been performed. Reflection coefficient is smaller than 0.5% for the full dynamic range, which is 12 bits. Relative linearity error is below 1%. Output noise is about 1 LSB after applying correlated double sampling.