impact ionization avalanche transit time (IMPATT)

The IMPATT (Impact Ionization Avalanche Transit-Time) diode is a microwave diode which, when steered into the characteristic range where the avalanche effect occurs, has a dynamic negative resistance.

In impatt diodes, this effect occurs in a frequency range determined by the delay time created by the charge of the carriers in the depletion zone. This is why the IMPATT diode is called an avalanche delay diode (LLD) in German. The avalanche transit time is thus decisive for the operating principle. The IMPATT diode is comparable to the Barritt diode, the Dovett diode and the Trapatt diode.

Impatt diodes can be used in the frequency range up to 100 GHz for microwave generation. Thus in transmitting devices for radar or for military applications.