1. 1 OSCILLATOR Bollen

2. 2 AGENDA Bollen What is oscillation Analog oscillation WIEN bridge oscillator High pass and low pass combined Relaxatin oscillator RC circuit 15k and 10 nF Voltage diviver 15k and 15k Comparator Signals and output Charge Discharge Frequency = 1 / total time Variationa Summary

3. 3 What is oscillation Bollen Circuit powered by Vcc and Vee No input signal, only output signal Wienbridge Oscillator; output signal is sine wave (used for making radio frequencies) Relaxation Oscillatoer; output signal is a “digital” block signal (used for clock or count circuits)

4. 4 What is analog oscillation WIEN bridge oscillator Bollen Barkhausen criterium: Loopgain = 1 Total phase = 0 or 360

5. 5 WIEN bridge oscillator Bollen Oscillator for High frequency Sine signals It uses 2 filters; High pass and low pass For one frequency the phase = 0 degrees !!!!

6. 6 High Pass and Low Pass combinated Bollen

7. 7 WIEN bridge oscillator Bollen Barkhausen criterium: Loopgain = 1 Total phase = 0 or 360

8. 8 WIEN bridge oscillator Bollen After “short” mathematics;

9. 9 WIEN bridge oscillator Bollen

10. 10 WIEN bridge oscillator Bollen

11. 11 WIEN bridge oscillator Bollen For phase = o degrees; imaginair part = 0

12. 12 WIEN bridge oscillator Bollen For R1 = R2 = R And C1 = C2 = C At oscillation IM = 0 Au = 1/3 so amplificaton should be +3 Rf = 2 Rs

13. 13 WIEN bridge oscillator Bollen

14. 14 What is “digital” oscillation Relaxation oscillator Bollen RC-circuit 15k and 10nF; charge / discharge Voltage divider 15k and 15k; high treshold / low treshold Comparator Output: block Vcc / Vee

15. 15 RC-circuit 15k and 10nF Bollen Vin = Vcc = +12 for charge And = Vee = -12 for discharge

16. 16 Voltage divider 15k and 15k Bollen Vin = +12 volt = opamp output high or Vin = - 12 volt = opamp output low V treshold up = +6 V for +12 opamp output V treshold low = -6 V for – 12 opamp output

17. 17 Comparator Bollen Inverting input; Uc, capacitor voltage Non inverting input; Treshold voltage, high (+6 Volt) or low (-6 volt) Output:

18. 18 Signals and output Bollen Blue = output signal (+12 Volt or – 12 Volt) Green = treshold signal (+6 Volt of – 6 Volt) Red = capacitor signal

19. 19 Charge Bollen R = 15 k C = 10 nF Vfinal = +12 V Vinitial = -6 V Switch at Vc = +6 Volt Calculate 2nd charge track! Why?

20. 20 Discharge Bollen R = 15 k C = 10 nF Vfinal = -12 V Vinitial = +6 V Switch at Vc = -6 Volt

21. 21 Frequency = 1 / (total time) Bollen

22. 22 Variations 1 Bollen By using diodes; Charge time and Discharge time are different !! Treshold remains the same So … duty cylce is controlable; up time ≠ down time

23. 23 Variations 2 Bollen Frequency control by changing the voltage divider Vtreshold up Vtreshold low

24. 24 Summary 1 Bollen Analyse yourself.. Conclusion?

25. 25 Summary 2 Bollen Analyse yourself.. Conclusion?