The front-end electronics system for the CMS electromagnetic calorimeter

CMS designed an high precision electromagnetic calorimeter, to be operated reliably in the high radiation environment of the CERN Large Hadron Collider (LHC), inside the 4 T magnetic field. Innovative solutions were developed to place the front-end electronics within the detector with the advantage of minimizing external noise, while reducing the number of optical links to send data to the off-detector readout. The final system architecture will be reviewed in detail. High resolution, over the wide energy dynamic range, was obtained with studies in an electron test beam.