Front-End Electronics for a TPC-Detector

The CERES/NA45-Collaboration upgrades the existing lepton-pair spectrometer at the CERN SPS with a TPC detector which improves the momentum resolution. We present the development of new front-end electronics to read out the nearly 20000 channels of the chamber. It is comprised of two circuits: (i) A continuously sensitive preamplifier with semi-Gaussian shaper and tailcancellation, which offers selectable time constants to cope with various detector gases. The design is based on a low noise charge sensitive amplifier with P-channel input device matched to 12 pF input capacitance with an equivalent noise charge ENC=120 e rms at 27 s peaking time. The CSA-Shaper features ENC=180 e rms at 580 ns peaking time. (ii) A 16 256 cell analog-memory stores the input waveform at 10 MHz during the drift-time of the chamber. Both circuits are developed in a 0.8 m CMOS technology and we will focus on the result of prototype measurements. Although the complete system is geared towards the CERES-TPC, its necessary flexibility make it feasible for the ALICE experiment.