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

We present a read-out system for large mass bolometric detectors. It consists of a differential voltage-sensitive preamplifier having very low series and parallel noise, thanks to the use of a pair of selected silicon JFET 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 which is sensitive to the shot noise generated by very small currents (tens of fA).