User manual

12
How the transistor works
A small current applied to the basis-emitter section can control a large
current on the collector-emitter section. I.e. if a low basis current is owing
(positive in NPN transistors, negative in PNP transistors), the transistor
will conduct the current from the collector to the emitter or vice versa. If no
current is owing through the basis or if the basis connection is with negative
(NPN) or positive potential (PNP), the transistor will block.
Fig. 008: Circuit symbols for NPN and PNP transistors.
1.7 Resistors
A resistor is a passive element in electrical and electronic circuits. Its main task is
reduction of the owing current to sensible values (also see chapter
»Light-Emitting Diodes«).
The best-known resistor build is the cylindrical ceramics carrier with axial
connection wires.