ABSTRACT
Feedback, whether intentional or parasitic, is pervasive of all electronic circuits and systems. In general, feedback is comprised of a subcircuit that allows a fraction of the output signal of an overall network to modify the effective input signal in such a way as to produce a circuit response that can differ substantially from the response produced in the absence of such feedback. If the magnitude and relative phase angle of the fed back signal decreases the magnitude of the signal applied to the input port of an amplifier, the feedback is said to be negative or degenerative. On the other hand, positive (or regenerative) feedback, which gives rise to oscillatory circuit responses, is the upshot of a feedback signal that increases the magnitude of the effective input signal. Because negative feedback produces stable circuit responses, the majority of all intentional feedback architectures is degenerative [1,2]. However, parasitic feedback incurred by the energy storage elements associated with circuit layout, circuit packaging, and secondorder high-frequency device phenomena often degrades an otherwise degenerative feedback circuit into either a potentially regenerative or severely underdamped network.
