Barkhausenkritérium

The Barkhausen criterion is a fundamental principle in electronics that describes the conditions under which an amplifier will oscillate. Named after German physicist Heinrich Barkhausen, it states that for sustained oscillations to occur in a feedback amplifier, two conditions must be met. First, the total phase shift around the feedback loop must be an integer multiple of 360 degrees, or 0 degrees. This means that the signal fed back to the input must be in phase with the original input signal, reinforcing it. Second, the magnitude of the loop gain must be equal to or greater than one. Loop gain is the product of the amplifier's gain and the gain of the feedback network. If the loop gain is less than one, any oscillations will die out. If it is exactly one, sustained oscillations at a stable amplitude will occur. If it is greater than one, the amplitude of the oscillations will increase until nonlinearities in the amplifier limit the output, effectively reducing the loop gain back to one. This criterion is crucial for the design of oscillators, which are circuits that generate repetitive electronic signals, such as sine waves or square waves. It is applied in various electronic devices, including radio transmitters, function generators, and clock circuits. Understanding and applying the Barkhausen criterion is essential for engineers designing and troubleshooting oscillating circuits.