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Class Exercise 10 (web version only)
10. Op-amp Circuits with Positive Feedback
10.1. Systems with positive feedback (PFB). Positive feedback principle: deriving the idea from many everyday situations (analogies); generalizing in a block diagram. Discussion: How are the negative feedback and positive feedback alike? How are they different? How do we convert a negative feedback system into a positive one and v.v.?
10.2. Comparators with hysteresis. Examples of the phenomenon - mechanical, thermal, electrical etc. Generalizing. Discussion: Is the hysteresis useful or harmful phenomenon in electronic circuits? How do we do a hysteresis (including a hysteresis into a comparator without hysteresis)? Can a comparator with hysteresis memorize (i.e. can we convert the comparator into a RS trigger)?
10.2.1. Inverting comparators with hysteresis. Converting non-inverting amplifier into inverting comparator. Visualizing the operation by potential diagram.
10.2.2. Non-inverting comparators with hysteresis. Converting inverting amplifier into non-inverting comparator. Visualizing the operation by potential diagram. Discussion: Why the circuit do not ever work properly?
10.3. Pulse generators.
10.3.1. Self-generating circuits of triangle and square signals. Deriving the idea from many everyday situations (analogies). Generalizing the idea in a block diagram containing an integrator and a comparator with hysteresis.
10.3.1.1. Square-wave generator. Assembling the circuit from a RC integrator and comparator with hysteresis. Linking with digital electronics - is it comparator with hysteresis timer 555? Discussion: Is the non-linear waveform a problem in this circuit?
10.3.1.2. Square- and triangle-wave generator. Assembling the circuit from an active RC integrator and comparator with hysteresis. Linking with digital electronics - assembling the circuit from RC integrator and timer 555.
Last updated June 28, 2004
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