The silicon microstrips tracker for CMS at LHC demands fast, radiation-hard electronics. An original solution was proposed for the processing of signals from silicon detectors. This technique allows precise reconstruction of the arrival time of the particles, even with a 'slow' shaping time and a limited power budget. This idea was already implemented in the APV6 circuit, designed in a bulk CMOS technology from Harris.In this paper, we present the version (APVD) designed in the CMOS SOI radiation hard technology DMILL by a French-British collaboration. The APVD is a 128-channel mixed analogue-digital: each channel includes a low-noise charge preamplifier, a CR-RC shaper with a peaking time of 50 ns, an analogue pipeline where the signal is sampled at 40 MHz, an analogue pulse shape processor and a current output multiplexer. The circuit integrates an 12C interface for easy control of the operating parameters. All the control current and voltages as well as a calibration pulse are generated internally by dedicated blocks. The design and first experimental results from the first version of the 128-channel APVD, will be presented in this paper. They show the circuit is fully functional and can be used for the CMS experiment.
