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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.
Project 57
PNP Transistor
Project 58
NPN Transistor
A transistor uses a small electric current
to control a large electric current. Here
pressing S2 makes a small current ow
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 ow in
the opposite direction. Here pressing
S2 makes a small current ow 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.
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