Cold electronics for the liquid argon hadronic end-cap calorimeter of ATLAS

This paper describes the on-detector electronics of the ATLAS hadronic end-cap calorimeter (HEC). The electronics is operated in liquid argon; therefore attention is paid to its performance at low temperatures. The core of the electronics are Gallium Arsenide (GaAs) preamplifiers. We present design, layout and results of various tests of the preamplifier chips and summing boards. The calibration and signal cables have been studied under laboratory conditions and the signal distortion is modeled. All parts of the electronics have been produced, tested and assembled on the calorimeter modules. The summary of the commissioning tests is presented.