The MAD, a full custom ASIC for the CMS barrel muon chambers front end electronics

To meet frontend electronics needs of CMS barrel muon chambers a full custom ASIC, named "The MAD", has been first developed by INFN of Padova and then produced in 80.000 pieces to equip the 180.000 drift tubes[l]. The task of this IC is to amplify signals picked up by chamber wires, compare them against an external threshold and transmit the results to the acquisition electronics. The chip, built using 0.8 mum BiCMOS technology, provides 4 identical chains of amplification, discrimination and cable driving circuitry. It integrates a flexible channel enabling/disabling feature and a temperature probe for monitoring purposes. The working conditions of the detector set requirements for high sensitivity and speed combined with low noise and little power consumption. Moreover, as the basic requirement for the frontend is the ability to work at very low threshold to improve efficiency and time resolution, a good uniformity of amplification between channels of different chips and very low offset for the whole chain are needed. The ASIC has been extensively and deeply tested resulting in good performances; particularly, big effort was put in testing radiation (neutron, gamma rays and ions) tolerance and ageing effects to check behaviour and reliability in LHC environment.