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Abstract

In the framework of the GERDA-Experiment at th e Gran Sasso National-Laboratory in Italy, noise measurements at the GERDA preampl ifier were performed during this Bachelor thesis. The aim of these measurements was the characterization of the ci rcuit and the investiga tion of possible improve- ments. The preamplifier consists of an initial field-effect transistor (FET) and an operational amplifier. The noise should depend on the characteristics of the tran sistor as well as on other influences like the feed- back resistor or the operational point of the FET. These conditions were varied during the measure- ments to analyze their influence on the different noise components. Actually, the FET BF862 is used in the GERDA-Experi ment. This transistor is only available in a package, whose material causes radioactive backgr ound and therefore brings additional background to the measurement. Because of this, a second FET, th e LSK170C, which is also available without pack- age, was tested. However, no improvements could be achieved. The measured noise parameters for serial and parallel noise were considerably higher than expected. With in this Bachelor thesis no satisfactory reason for these high values could be stated