1. Oscillator Foundations of Technology Oscillator © 2013 International Technology and Engineering Educators Association, STEM  Center for Teaching and Learning™ Foundations of Technology Teacher Resource Unit 4 Lesson 4

2. Objective: 1.You will build a simple circuit - two transistor audio oscillator that will generate an audio tone in a speaker.

3. You will need the following parts from your kit: 1.Breadboard 2.10 ohm resistor 3.47 ohm resistor 4.120,000 ohm resistor 5.0.1 uF (104) capacitor 6.NPN transistor 7.PNP transistor 8.9 volt battery lead 9.4 wires 10.9 volt battery 11.Speaker

4. Use this schematic to construct the experiment. 47 Ohm + - 9 volts 120K Ohm 10 Ohm 3904 3906

5. Your circuit should like this one.

6. This circuit will make a sound. 1.Using two transistors, it will generate a fixed frequency. 2.By changing the 120K Ohm and/or the 47 Ohm resistor, it will cause the frequency to change. 3.Changing the capacitor will also have an effect on the frequency. 4.Do not change the 10 Ohm resistor as this is the only thing in place to protect the speaker.

7. 1.Connect the 9 volt battery. 2.Listen to the speaker. 3.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?

8. 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.