User Manual

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You can check the pins of the buzzer, the longer one is the anode and the shorter one is the
cathode. Please don’t mix them up when connecting, otherwise the buzzer will not make
sound.
Transistor
The transistor is a semiconductor dev ice that controls current by current. It functions by
amplifying weak signal to larger amplitude signal and is also used as a non-contact sw itch.
A transistor is a three-layer structure composed of P-type or N-type semiconductors. They
form the three regions internally. The thinner in the middle is the base region; the other two
are all N-type or P-type ones – the smaller region with intense majority carriers is the emitter
region, w hen the other one is the collector region. This composition enables the transistor to
be an amplifier.
From these three regions, three poles are generated respectiv ely, which are base (b), emitter
(e), and collector (c). They form two P-N junctions, namely, the emitter junction and
collection junction. The arrow in the circuit symbol indicates the direction of emitter junction.
Transistors can be divided into two kinds: the NPN and PNP one. The former is made of two
N-type semiconductors and one P-type and that the latter is the opposite. See the figure
below.
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