SPEAKER: Christine Hu, IReS, Strasbourg France 


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to be submitted
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A new integrated circuit (APVD_DC) for the front-end electronic of the silicon  tracker of CMS has been realized in the radiation-hard technology DMILL. DC-coupled silicon micro-strip detectors have significant economical advantages compared to AC-coupled devices due to their less complex  fabrication chain and better yield. This circuit allows the use of DC-coupled silicon detectors  with significant leakage currents as expected from irradiation after several years of LHC operation.
In this paper, a solution is presented with an active leakage current  compensation for each input channel. The APVD_DC  contains, like other  members of the APV family 128 identical analog channels, each one composed of a low noise preamplifier, a CR-RC shaper, an analog pipeline of 160 cells and a signal processing stage.  A current compensation circuit is added in every  preamplifier to sink the leakage current coming from the detector. Good performance of the circuit has been measured on APVD_DC prototypes  for leakage currents of over 10 micro Ampere.

Because all previous APVD circuits suffered from an instability problem  the analog stage of the circuit occurring at nominal bias values,  this paper will also present a detailed study of this phenomena by  specific tests and extensive simulations and will describe an implemented  solution which stops the oscillation of the circuit.
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