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(μ-PIC). The design of this ASD IC is based on the ASD IC for the Thin Gap Chamber(TGC-ASD) in the LHC Atlas Experiment. The integration constant of the preamplifier is 5 times longer than that of the TGC-ASD, and some other modifications have been done in order to improve the signal to noise ratio of the μ-PIC. The ASD IC uses SONY Analog Master Slice bipolar technology. The IC contains 4 channels in a QFP48 package. The integration constant of the preamplifier is 80ns and its gain is approximately 0.8V/pC. The output from the preamplifier is received by a shaper(main-amplifier) with a gain of 7. The baseline restoration circuit is incorporated in the main-amplifier and the current source is 5 times smaller than the TGC-ASD. The threshold voltage for the discriminator section is common to the 4 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 50pF is around 2000 electrons. The power dissipation with LVDS outputs (100Ω load) is 57mW/ch. Using this ASD, the analog output voltage from the signal of the μ-PIC is about twice higher than the case of using the TGC-ASD. As a consequence, the MIPs tracking performance of the Time Projection Chamber(TPC) with the μ-PIC was highly improved. Performance of the ASD-IC and improved tracking performance of the TPC are reported.