The Operational Amplifier (op-Amp) and its basic amplifying configurations
Chapitre 1. Introduction to the Operational Amplifier
1.1. Vocabulary
1.2. Use
1.3. Power supply
1.4. Diagram
1.5. Ideal model
1.6. Positive and negative feedback
1.6.1. Positive feedback
1.6.2. Negative feedback
Chapitre 2. Basic amplifier configurations
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1.6.1. Positive feedback

If ε increases (following a decrease of Ve) then,
Vs = Aε
increases,
V+ = αVs
increases,
ε = V+ - V-
increases

The positive feedback makes the system unstable: a small perturbation results in a chain reaction that leads Vs to the saturation. This is a nonlinear behavior.


Analogy : the instability of a marble on a reversed cup.
ε
represents the distance from the equilibrium position.

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