17-07-2012, 04:37 PM
Regenerative Feedback System, Astable & Monostable Multivibrator
Regenerative Feedback System, Astable & Monostable Multivibrator.docx (Size: 188.5 KB / Downloads: 24)
AIM:
This experiment illustrates the use of positive regenerative feedback, which is used in all on-off control systems such as temperature controllers, pulse width modulators and Class-D amplifiers. The goal of this experiment is to understand the basics of hysteresis and the need of hysteresis in switching circuits.
Theory:
Astable Multivibrator:
An astable multivibrator is shown in Figure. The square and the triangular waveforms shown in the fingure are both generated using the astable. We refer to yas the regenerative feedback factor. The time period of the square waveform generated by by the multivibrator is given by
Lu( t +r!p +X... _6_9_._.y,y .
Monostable Multivibrator:
The circuit diagram for a monostable multivibrator is shown. The trigger waveform shown in Figure is applied to the monostable. The negative edge triggers the monostable, which produces the square waveform shown in Figure. The monostable remains in the .on. state until it is triggered; at this time, the circuit switches to the .off. state for a period equal to Ʈ. The equation for .is shown below
Ʈ= R C ln(1/1-β)
RESULTS:
1. We designed the Astable multivibrator, Mono stable multivibrator and Schmitt trigger.
2. For the Astable circuits we plotted the waveform form the oscilloscope.
3. Mono stable circuit we plotted the transient analysis.
4. Schmitt trigger we have plotted the transient response and the hysteresis curve and we have tabulated for different values of regenerative feedback.