1. Signal Generators
Oscillators
November 2, 2007

2. HW:
Due Friday Nov ,13.14,13.23,13.27
November 2, 2007

3. SIGNAL GENERATORS /OSCILLATORS
A positive-feedback loop is formed by an amplifier and a frequency-selective network
In an actual oscillator circuit, no input signal will be present
November 2, 2007

4. Oscillator-frequency stability
November 2, 2007

5. Limiter Ckt Comparator
November 2, 2007

6. Wien-bridge oscillator
without amplitude stabilization.
November 2, 2007

7. Wien bridge w/ Amp. Stabil.
limiter used for amplitude control.
November 2, 2007

8. Alternate Wien bridge stabil.
November 2, 2007

9. Phase Shift Oscillator
November 2, 2007

10. Phase Shift. Osc. W/ Stabil.
November 2, 2007

11. Quad Osc. Circuit
November 2, 2007

12. Active Tuned Osc.
November 2, 2007

13. OPAMP based Tuned Amp. Osc.
November 2, 2007

14. Colpitts and Hartley Oscillators
November 2, 2007

15. Equiv. Ckt To simplify the analysis, negtlect Cm and rp
Consider Cp to be part of C2, and include ro in R.
November 2, 2007

16. Collpits Oscillator
November 2, 2007

17. Piezzoelectric Crystal
November 2, 2007

18. CMOS inverter as an amplifier.
Pierce Oscillator
CMOS inverter as an amplifier.
November 2, 2007

19. Bistable Operation
November 2, 2007

20. Bistable
November 2, 2007

21. November 2, 2007

22. Hysteresis
November 2, 2007

23. Noisy Signal
November 2, 2007

24. Limiter (b) L+ = VZ + VD1 + VD2 and L– = –(VZ + VD3 + VD4).
a) L+ = VZ1 + VD and L– = –(VZ2 + VD),
Limiter circuits = more precise output levels for bistable circuit.
R according to current required for the proper operation of the zener diodes.
November 2, 2007

25. Astable w/ feedback
Abistable multivibrator with inverting transfer characteristics in a feedback loop with an RC circuit results in a square-wave generator.
November 2, 2007

26. Astable
The circuit obtained when the bistable multivibrator is implemented with the circuit
(This circuit is called an astable multivibrator.)
c) Waveforms at various nodes of the circuit in (b).
November 2, 2007

27. Ckt for triang/square wave
A general scheme for generating triangular and square waveforms.
November 2, 2007

28. (a) An op-amp monostable circuit
(a) An op-amp monostable circuit. (b) Signal waveforms in the circuit of (a).
November 2, 2007

29. internal circuit of the 555 integrated-circuit timer.
555 IC
internal circuit of the 555 integrated-circuit timer.
November 2, 2007

30. 555 for monostable
a) The 555 timer connected to implement a monostable multivibrator. (b) Waveforms of the circuit in (a).
November 2, 2007

31. 555 for astable
The 555 timer connected to implement an astable multivibrator. (b) Waveforms of the circuit in (a).
November 2, 2007

32. Triangle  Sinusoid
Using a nonlinear (sinusoidal) transfer characteristic to shape a triangular waveform into a sinusoid.
November 2, 2007

33. (a) A three-segment sine-wave shaper
(a) A three-segment sine-wave shaper. (b) The input triangular waveform and the output approximately sinusoidal waveform.
November 2, 2007

34. A differential pair with an emitter degeneration resistance used to implement a triangular-wave to sine-wave converter.
November 2, 2007

35. Superdiode
when vI > 0 and the diode conducts, the op amp supplies the
load current, and the source is conveniently buffered,
an added advantage.
sedr42021_1333a.jpg
(a) The “superdiode” precision half-wave rectifier and (b) its almost ideal transfer characteristic.
November 2, 2007

36. The transfer characteristic for R2 = R1.
An improved version of the precision half-wave rectifier: Diode D2 is included to keep the feedback loop closed around the op amp during the off times of the rectifier diode D1, thus preventing the op amp from saturating.
The transfer characteristic for R2 = R1.
November 2, 2007