Amplified current
11
On the eleventh day you will receive an
important component of your calendar:
the transistor. The transistor has three
connections which should not be confused
with each other. They are called emitter
(E), base (B) and collector (C). By the way,
the abbreviation C comes from the English
spelling (collector). The emitter should
be connected to the negative terminal of
the battery. The flat, labelled side of the
transistor must point to the left.
The experiment shows the typical behaviour
of a transistor. If the pushbutton switch is
still open, the green LED shines dim, but
the red LED is very bright. If you press the
button, the red LED goes out. The transistor
Transistors
The transistor in your experiment
contains a silicon crystal. Silicon
(Si) is contained in large quantities
in normal quartz sand (quartz =
silicon oxide). It belongs to the
group of semiconductors, i.e.
substances that neither conduct
electricity well, such as metals, nor
insulate it well, such as glass or
rubber. In order to achieve a very
specific conductivity, tiny traces
of other substances are added to
the pure silicon. Depending on the
type of these substances, N-silicon
or P-silicon is obtained. There
are three layers in your transistor:
NPN. Other types have a different
layer sequence, namely PNP.
They function similarly, but with a
different current direction.
Transistors are important
components in all areas of
electronics, in radios and
televisions as well as in
smartphones and computers.
Transistors are installed
everywhere. It is therefore
worthwhile to understand exactly
how a transistor works.
Take a good look
at your transistor.
There’s a label:
BC547B. With
this description
you can order exactly the right
transistor, which is manufactured
by several companies by the way.
Or you can search the Internet
for the data sheet of this type. It
contains many properties and
measured values, some of which
are only clearly understood by
experts. In a nutshell: This NPN
transistor can withstand a voltage
of 50 V and a current of 100 mA.
And it can amplify the current at
least 200 times.
behaves like a switch. A small current
through the basic connection causes a
large current to be switched on through
the collector connection. However, if
you connect the base and emitter via the
button or pull out the green LED, the
red LED will also turn off.
