Front-end electronics for the CERES 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 20 000 channels of the chamber. It is comprised of two circuits: (i) A continuously sensitive preamplifier with a semi-Gaussian shaper and tail-cancellation, which offers selectable time constants to cope with various detector gases. The design is based on a charge-sensitive amplifier with PMOS input transistor which gives low-noise (∼600e rms) at 15 pF input capacitance and 400 ns peaking time. (ii) A 16×256 cell analog-memory stores the input waveform at 14 MHz during the drift time of the chamber. A 16 channel successive approximation ADC sequentially digitizes the signal at 1 MHz with 8 bit precision. Both circuits are developed in a 0.8 μm CMOS technology. We will focus on the result of prototype measurements and will discuss the feasibility to use this development for the ALICE TPC as well.