Design and results from the APV25, a deep sub-micron CMOS front-end chip for the CMS tracker

The APV25 is a 128-channel analogue pipeline chip for the readout of silicon microstrip detectors in the CMS tracker at the LHC. Each channel comprises a low noise amplifier, a 192-cell analogue pipeline and a deconvolution readout circuit. Output data are transmitted on a single differential current output via an analogue multiplexer. The chip is fabricated in a standard 0.25 mm CMOS process to take advantage of the radiation tolerance, lower noise and power, and high circuit density. Experimental characterisation of this circuit shows full functionality and good performance both in pre- and post-irradiation (20 Mrad) conditions. The measured noise is significantly reduced compared to earlier APV versions. A description of the design and results from measurements prior to irradiation are presented.