-32-
This is designed to help you study the switching
action of the transistors in turning on the LED. You
will use two different transistors – the NPN type and
one of two PNP types included in your kit. NPN and
PNP refer to the arrangement of the semiconductor
materials that make up the transistors.
The 47k
Ω
resistor supplies a base voltage so that
the NPN transistor at the bottom of the schematic
stays on. The PNP transistor at the top of the
schematic turns on when you close the switch and
make the connection through the 22k
Ω
resistor.
Because the 22k
Ω
resistance is about half that of
the 47k
Ω
resistor, the current supplied to the base
of the PNP transistor is about twice as much as that
of the NPN. The PNP is therefore “more” on than the
NPN.
Hook up the circuit and press the key: 1 is displayed.
To increase the base current of the NPN transistor,
decrease the value of the 47k
Ω
resistor connected
to the base – terminal 46. Simply disconnect
terminals 87 and 88, and replace them with
connections to another resistor. For example,
change connections 87-42 and 46-88, to 83-42 and
84-46 to change the 47k
Ω
resistor to a 10k
Ω
resistor. Each time you use a lower value resistor,
more current is supplied to the base of the
transistor, and the LED display lights a little brighter
when you use the key. Don’t decrease the
resistance below 1k
Ω
, or the transistor might burn
out.
Now change the resistors to 10k
Ω
and press the
key. Use terminals 81 and 82, and terminals 83 and
84. The brightness should not change much with
transistors both fully on. If much change does occur,
check the batteries. They might be weak.
Notes:
EXPERIMENT #19: TRANSISTOR SWITCHER
Wiring Sequence:
o
21-23-41
o
25-47
o
40-85
o
87-42-119
o
46-88
o
124-48-137
o
86-138
o
121-122
Schematic
Содержание EP-130
Страница 11: ... 11 I ENTERTAINMENT CIRCUITS ...
Страница 26: ... 26 II BASIC SEMICONDUCTOR AND COMPONENTS CIRCUITS ...
Страница 36: ... 36 III LED DIGITAL DISPLAY CIRCUITS ...
Страница 41: ... 41 IV A TOUR THROUGH DIGITAL CIRCUITS ...
Страница 49: ... 49 V MORE ADVENTURES WITH DIGITAL CIRCUITS ...
Страница 64: ... 64 VI THE WORLD OF TRANSISTOR TRANSISTOR LOGIC ...
Страница 77: ... 77 VII APPLICATION CIRCUITS BASED ON THE OSCILLATOR ...
Страница 88: ... 88 VIII BASIC OPERATIONAL AMPLIFIER CIRCUITS ...
Страница 116: ... 116 IX MORE ADVENTURES WITH OPERATIONAL AMPLIFIERS ...
Страница 129: ... 129 X COMMUNICATION CIRCUITS ...
Страница 136: ... 136 XI TESTING AND MEASURING CIRCUITS ...