Positive and Negative Feedback in Engineering and Biology

No other concepts have shaken so deeply the bases of engineering like those of positive and negative feedback. They have played a most prominent role in engineering since the beginning of the previous century. The birth certificate of positive feedback can be traced back to a pair of patents by Edwin H. Armstrong in 1914 and 1922, whereas that of negative feedback is already lost in time. We present in this paper a short review on the feedback's origins in the fields of engineering and biology. Besides, we compare the main feedback's ideas in control theory and system biology in order to get a better understanding of the lactose and tryptophan operons' regulatory systems (control systems). It is obvious that we need to know the genome of an organism in order to understand how it works, but that is only half of the puzzle, for we also need to know how the underlying genetic regulatory systems work in order to get a complete picture of the cell's dynamics.