Step recovery diode
The step recovery diode or Abreißdiode ( engl. step recovery diode, SRD, also snap -off diode) is a special case of the charge storage diode. A step-recovery diode from forward direction reversed in the reverse direction, a current flows in the reverse direction, without the voltage across the diode will change significantly for a defined time (about 0.1 to 3 ns). Only then, when the free charge carriers are depleted, the current suddenly collapses ( the SRD is a so-called "hard" diode), and the voltage can quickly take high values in the reverse direction.
Because of the " sudden " switching from a nearly ideal short circuit to a power - blocking behavior of an applied sinusoidal voltage is distorted strongly non-linear and there are harmonics. Memory switching diodes with a short turn-off time, therefore, to be used for the multiplication of several gigahertz frequencies in the range of about one (frequency doubler and tripler, generating a " frequency comb ", so many high harmonics of a lower frequency ). The step recovery diode also has applications in the pulse shaping, for example, generating the sharp pulse edges or short pulses when the input signals with a relatively slow rise or fall of the voltage. The shortest pulses can be generated is about 100 ps long.
A rule memory switching diodes have a pin structure. The small thickness of the i-layer and the resulting high electric field in the i-type layer (in spite of low voltages ) are the cause of the rapid disappearance of the minority charge carriers in the change of flow direction. However, the lifetime of the minority charge carriers without an applied field is substantially larger (on the order of 100 ns ). Because of the thin i- layer, the most memory switching diodes have relatively low permissible reverse voltages ( below 100 V).
In contrast to memory switching diodes most other types of semiconductor diodes are built so that the current " soft " switches off to prevent voltage spikes due to unavoidable inductances.
The first step recovery diodes were developed in the early 1960s and counted for a long time one of the fastest components of the conventional semiconductor technology.