An amplifier-shaper-discriminator with baseline restoration for the ATLAS transition radiation tracker

The ASDBLR is a bipolar integrated circuit that provides eight channels of amplifier, shaper, discriminator and baseline restorer on a 6.17 by 4.78 mm 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 (≈8 ns), good double pulse resolution (≈40 ns), low power (<30 mW/ch), and low operational threshold (≈1.5 fC) led to the choice of a largely differential circuit which includes detector tail compensation. A capacitively-coupled baseline restorer eliminates effective threshold shifts that would otherwise occur at the high per-wire hit rates (up to 20 MHz). A full-scale dynamic range of 200 fC and two discriminators with separate threshold adjusts allow the ASDBLR to function both as a tracker and a TR photon detector. Selectable ion-tail compensation makes the circuit compatible with both CF4 and Xe-based gases