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Page 25
Zener diodes
Zener diodes are used for limiting voltages. In contrast to
"normal" diodes they are not destroyed when the limit voltage
is exceeded.
Capacitors
Among other things capacitors are used for filtering interference
voltages or as frequency determining parts. Ceramic capacitors
are not polarized, for that reason their mounting orientation is
of no importance. Normally they are marked with a three-digit
number which indicates the value coded.
Value
Number
1 nF
102
100 nF
104
Electrolytic capacitors
Electrolytic capacitors are often used to store energy. In
contrast to ceramic capacitors they are polarized. One of the
two leads is marked with a minus sign which indicates the
mounting orientation. The value is given on the casing.
Electrolytic capacitors are available with different voltage
sustaining capabilities. Using an electrolytic capacitor with a
voltage sustaining capability higher than required is always
possible.
Transistors
Transistors are current amplifiers which convert low signals into
stronger ones. They have three contacts. As they are polarized,
they have to be mounted in a certain direction.
The BD types have a flat housing (TO-housing) with the type
designation printed on the front side. The metallic rear is
unlabelled, on the PCB layout the rear is marked by a thick line.