Half power point

The half-power point is the point at which the output power has dropped to half of its peak value; that is, at a level of approximately -3 dB. In filters, optical filters, and electronic amplifiers, the half-power point is also known as half-power bandwidth and is a commonly used definition for the cutoff frequency. In the characterization of antennas the half-power point is also known as half-power beamwidth and relates to measurement position as an angle and describes directionality. Amplifiers and filters This occurs when the output voltage has dropped to (~0.707) of the maximum output voltage and the power has dropped by half. A bandpass amplifier will have two half-power points, while a low-pass amplifier or a high-pass amplifier will have only one.