A low DC drift read-out system for a large mass bolometric detector

We present a read-out solution for a bolometric detector of large mass. It consists of a voltage-sensitive preamplifier, having very low series and parallel input noise, thanks to the use of a pair of selected silicon JFETs at the input. Very good electrical characteristics were obtained. DC power supply rejection ratio, thermal drift of input offset voltage and input leakage current are minimized by using novel circuit solutions. Parallel noise behavior was also investigated using a new measurement method capable to be sensitive to shot noise generated by very small currents (tens of fA)