Low noise, low power front end electronics for pixelized TFA sensors

Thin Film on ASIC (TFA) technology combines advantages of two commonly used pixel imaging detectors, namely, Monolithic Active Pixels (MAPs) and Hybrid Pixel detectors. Thanks to direct deposition of a hydrogenated amorphous silicon (a- Si:H) sensor lm on top of the readout ASIC, TFA shows the similarity to MAP imagers, allowing, however, more sophisticated front–end circuitry to extract the signals, like in case of Hybrid Pixel technology. In this paper we present preliminary experimental results of TFA structures, obtained with 10 μm thick hydrogenated amorphous silicon sensors, deposited directly on top of integrated circuit optimized for tracking applications at linear collider experiments. The signal charges delivered by such a-Si:H n-i-p diode are small; about 37 e-/μm for minimum ionizing particles, therefore a low noise, high gain and very low power of the front- end are of primary importance. The developed demonstrator chip, designed in 250 nm CMOS technology, comprises an array of 64 by 64 pixels laid out in 40 μm by 40 μm pitch.