Manual

-79-
N
ow you will build an oscillator using two transistors
connected directly to each other. As you have
witnessed, there are many ways to make an
o
scillator. This way is easier compared to some.
After finishing the wiring, press the key. You hear a
beep sound coming from the speaker. Now rotate
the control. How does it change the sound?
The two transistors collaborate with each other and
act as a single transistor. The NPN transistor
amplifies the signal from the 22kW resistor and
sends it to the PNP transistor, to obtain a larger
output.
The frequency of the oscillation is determined by the
capacitor. The project starts with the 0.01mF
capacitor in the circuit but you can experiment with
alternate value capacitors. The control alters the
voltage leading to the base of the NPN transistors.
It alters the tonal quality as well as the frequency.
You should be sure to record your results like a
professional scientist, so you can repeat the
experiment later. If you alternate capacitor values,
be sure to observe the polarity (+ and –) of the
electrolytic capacitors.
N
otes:
EXPERIMENT #61: DOUBLE-TRANSISTOR OSCILLATOR
Wiring Sequence:
o 1-29
o 2-30
o 3-48-138
o 5-101-44
o 26-45-76
o 27-85
o 28-124-137
o 46-102-86
o 47-43
o 75-119
o 121-122
Schematic
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