A Front End Electronic card using a high gain and high bandwidth preamplifier with a fast discriminator for time of flight measurements

During the development of the Multi Strip Multi Gap Resistive Plate Chambers (MMRPCs) for the FOPI Time of Flight (ToF) upgrade, we designed different versions of the Front End Electronics (FEE). The signals from a MMRPCs, which are typically between 1-30 mV, are read out on each side of the strips by a preamplifier followed by a leading edge discriminator. The signals are digitized in a Time-to-Amplitude Converter (TAC) and a QDC. These counters are designed to provide a ToF measurement below σ_t <60ps which needs a preamplifier-discriminator stage with an intrinsic electronic resolution below σ_t(FEE) < 20ps. We show the design steps of the FEE-card from a 4 channel (FEE1) design for the R&D phase to the final 16 channel card (FEE5) used for the mass production. Through these design steps, we kept the following key characteristics for the FEE: Low noise σn < 25 μV RMS (to the preamplifier input), high gain (200) and a high bandwidth (1GHz).