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 c onsists of a differential voltage-sensitive preamplifier having very l ow series and parallel noise, thanks to the use of a pair of selected silicon JFET at the input. Very good electrical characteristics were o btained. DC power supply rejection ratio, thermal drift of input offse t voltage and input leakage current are minimized by using novel circu it solutions. Parallel noise behavior was also investigated using a ne w measurement method which is sensitive to the shot noise generated by very small currents (tens of fA).