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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
