AN AMPLIFIER-SHAPER-DISCRIMINATOR WITH BASE-LINE RESTORATION FOR THE ATLAS TRANSITION RADIATION TRACKER

The ASDBLR is a bipolar integrated circuit that provides eight channel s of amplifier, shaper, discriminator and baseline restorer on a 6.17 by 4.78mm silicon substrate. It is designed for use in the straw-based Transition Radiation Tracker (TRT) of the ATLAS detector at the LHC. Competing requirements for short measurement time (approximate to 8ns) , good double pulse resolution (approximate to 40ns), low power (<30mW /ch), and low operational threshold (approximate to 1.5fC) led to the choice of a largely differential circuit which includes detector tail compensation. A capacitively-coupled baseline restorer eliminates effe ctive threshold shifts that would otherwise occur at the high per-wire hit rates (up to 20MHz). A full-scale dynamic range of 200fC and two discriminators with separate threshold adjusts allow the ASDBLR to fun ction both as a tracker and a TR photon detector. Selectable ion-tail compensation makes the circuit compatible with both CF4 and Xe-based g ases.