Download Slide 1

Foundations of Technology
Oscillator
Teacher Resource Unit 4 Lesson 4
© 2013 International Technology and Engineering Educators Association,
STEMCenter for Teaching and Learning™
Foundations of Technology
Objective:
1.
You will build a simple circuit - two
transistor audio oscillator that will
generate an audio tone in a speaker.
You will need the following parts from your kit:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Breadboard
10 ohm resistor
47 ohm resistor
120,000 ohm resistor
0.1 uF (104) capacitor
NPN transistor
PNP transistor
9 volt battery lead
4 wires
9 volt battery
Speaker
Use this schematic to construct the experiment.
3904
3906
47 Ohm
120K Ohm
+
9 volts
10 Ohm
Your circuit should like this one.
1.
2.
3.
4.
This circuit will make a sound.
Using two transistors, it will generate a fixed
frequency.
By changing the 120K Ohm and/or the 47 Ohm
resistor, it will cause the frequency to change.
Changing the capacitor will also have an effect on
the frequency.
Do not change the 10 Ohm resistor as this is the
only thing in place to protect the speaker.
1.
2.
3.
Connect the 9 volt battery.
Listen to the speaker.
You should hear a tone about 500 Hz.
Troubleshooting:
1. Check the battery. Does it have voltage?
2. Are there any breaks in the circuit?
3. Are the transistors in the right way?
By completing this experiment, you should have
heard a tone from the speaker. By changing the
resistors or capacitors, the frequency from the
speaker should have changed.
In complete sentences, write what you learned about
an oscillator.