Development of an ASD IC for the micro pixel chamber

A new amplifier-shaper-discriminator (ASD) chip was designed and manufactured for the micro pixel chamber (/spl mu/-PIC). The design of this ASD IC is based on the ASD IC (TGC-ASD) for the thin gap chamber in the LHC ATLAS Experiment. The decay time constant of the preamplifier is five times longer than that of the TGC-ASD, and some other modifications have been made to improve the signal-to-noise ratio of the /spl mu/-PIC. The ASD IC uses SONY Analog Master Slice bipolar technology. The IC contains four channels in a QFP48 package. The decay time constant of the preamplifier is 80 ns and its gain is approximately 0.8 V/pC. The output from the preamplifier is received by a shaper (main-amplifier) with a gain of 7. A baseline restoration circuit is incorporated in the main-amplifier, and the current used for the baseline restoration is five times smaller than that of the TGC-ASD. The threshold voltage for the discriminator section is common to the four channels and their digital output level is LVDS-compatible. The ASD IC also has an analog output of the preamplifier. The equivalent noise charge at the input capacitance of 50 pF is around 2000 electrons. The power dissipation with LVDS outputs (100/spl Omega/ load) is 57 mW/ch. Using this ASD, the analog output voltage from the signal of the /spl mu/-PIC is about two times higher than the case of using the TGC-ASD. As a consequence, the MIPs tracking performance of the time projection chamber (TPC) with the /spl mu/-PIC was improved. The performance of the ASD IC and an improved tracking performance of the TPC are reported.