User Manual

Turn on the slide switch (S1) - nothing happens. Now push the press
switch (S2) and the red LED (D1) lights, but the green LED (D2) stays
off.
Turn on the slide switch (S1) - nothing happens. Now push the press
switch (S2) and the red LED (D1) lights but the green LED (D2) stays
off.
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Project 158
PNP Transistor
Project 159
NPN Transistor
A transistor uses a small electric current to
control a large electric current. Here
pressing S2 makes a small current flow out
of the PNP transistor (Q1) through the
green LED, which triggers a large current
out of the transistor through the red LED.
The green LED is actually turned on, but
is so dim you may not be able to see it
even in a dark room.
The NPN transistor (Q2) is just like the
PNP transistor (Q1) in preceding circuit,
except that the electric currents flow in the
opposite direction. Here pressing S2
makes a small current flow into the
transistor through the green LED, which
triggers a large current into the transistor
through the red LED. The green LED is
actually turned on, but is so dim you may
not be able to see it even in a dark room.