Self-tuned regenerative amplification and the hopf bifurcation

Recent work in cochlear amplifier modeling has focused on systems which show the dynamics of a Hopf bifurcation. We show that these systems are examples of a generic amplifier topology, the self-tuned regenerative amplifier (STRA). The STRA is a feedback-stabilized regenerative amplifier that can be operated in a region of supercritical stability. The signatures of Hopf amplification, such as a cubic nonlinear small-signal response at resonance, are general features of the topology. The topology is shown to include a degenerate parametric amplifier, which may explain its low noise and insensitivity to input-feedback phase mismatch.