A novel technique for fast pulse-shaping using a slow amplifier at LHC

Abstract

We describe a new technique for front end signal processing for LHC type applications, where a shaping amplifier with a time constant of several beam crossing intervals is used. The method is based on discrete time filtering of data extracted from an analog pipeline after a first level trigger. A finite impulse response type filter deconvolutes the sampled voltages of the shaped pulse to retrieve the original impulse signal with high precision. Measurements showing the performance of the technique and its implication for signal to noise are presented. The method is well matched to CMOS front ends, where low power consumption and low noise is achieved for silicon strip readout by utilizing pulse shapes with time constants ∼ 50 ns. A CMOS circuit emulating the filter has been built. It has been implemented with very low power consumption (< 0.1 mW) in a small silicon area to be utilized on every channel in the system.