The front-end electronics system for the CMS electromagnetic calorimeter

The CMS electromagnetic calorimeter at the CERN Large Hadron Collider (LHC) has been designed to measure the energy of electrons and photons with high resolution over a wide dynamic range, using lead tungstate scintillating crystals. To minimize external noise most of the readout chain must be placed within the detector in a high radiation environment, inside the 4 T magnetic field. To cope with these demanding constraints innovative solutions have been adopted since most of the common technologies are excluded. The basic architecture and the first prototype tests of the on-detector readout chain are described.