What is the result of excessive positive feedback in an amplifier stage?

Positive feedback occurs when a portion of an amplifier's output signal is fed back into its input in the exact same phase. When this feedback becomes excessive, the amplifier begins to self-sustain the signal without any external input. This self-sustaining condition causes the amplifier to generate its own continuous AC signal, meaning "oscillations appear." In fact, this is exactly how electronic oscillators are intentionally designed to generate radio frequencies. However, in a standard amplifier stage meant only to boost a signal, this is usually an unwanted defect. The options regarding flattened frequency response or minimized distortion actually describe the beneficial effects of negative feedback, where the signal is fed back out of phase.