An amplifier is an electronic device that increases the voltage, current, or power of a signal. Feedback is defined as part of the output signal being returned to the input. Positive feedback occurs when the feedback signal is in phase with the original input signal, while negative feedback occurs when they are out of phase. Positive feedback is used in oscillators to generate an output frequency and in amplifiers to produce smooth signals from noisy inputs, but it increases gain and the risk of oscillation while reducing frequency response and increasing distortion.