1. Transistor Oscillators
A particular kind of transistor

2. What is Oscillation?
When speakers go into FEEDBACK and make a howling sound, they have broken into oscillation.

3. What is an Oscillator?
An oscillator is a circuit that is deliberately designed to oscillate.

4. What is an Oscillator?
An oscillator is a circuit that is deliberately designed to oscillate.
All oscillators are amplifiers with positive feedback.

5. What is an Oscillator?
Oscillators are used in radio and TV receivers for frequency control and for detection and mixing.

6. What is an Oscillator?
Oscillators are used in radio and TV receivers for frequency control and for detection and mixing.
Audio frequency oscillators are used in music synthesizers, FAX modems, doorbells, beepers, sirens, alarms,etc.

7. FEEDBACK Feedback can be in phase or out of phase. In phase means
Crests and troughs
Come at same time

8. FEEDBACK Feedback can be in phase or out of phase. Out of phase means
Crests and troughs
Come at opposite
times

9. For a circuit to oscillate
The feedback must be IN PHASE or positive.

10. For a circuit to oscillate
The feedback must be IN PHASE or positive.
Negative feedback reduces the gain.

11. Three Part of an Oscillator
Here is the logic of an oscillator
1. Wave producing circuit
2. Amplifier circuit
3. Output to load
4. Positive feedback circuit

12. Transistor Oscillator Circuits
Generate a constantly increasing and decreasing current.
The frequency of the varying current is how many times per second the current increases and decreases.
The unit of measure for frequency is Hertz (Hz) which represents one complete cycle per second.

13. In Mr Circuit Lab
In our lab, the frequency of oscillation of the circuit and thus the speaker, is determined by the values of R1 and C1. The larger R1 and C1, the lower the frequency of oscillation.
(Where R1 is resistance and C1 is capacitance)