Pulse discrimination by Gunn-effect switching

Abstract

Starting with simple equations for the domain dynamics the switching behaviour of a Gunn device with an ohmic load resistance is investigated, in a way similar to tunnel diode switching. An appropriate load line shall define three bias states on the current voltage characteristic, i.e. a homogeneous low-field state I ( E I < E peak), a homogeneous high-field state III ( E III > E valley) and a steady-state domain state IV. Then triggering the device from the only d.c. stable state I by (rectangular and triangular) input pulses of various heights and lengths leads to three types of switching processes namely direct return to I, return via state III or via state IV, these transitions yielding three typical output pulses. Discrimination curves for the input-pulse parameters are presented. Simple limiting cases for the three switching processes are treated in some detail yielding the switching times typical for each transition. Finally, the long-time stability of the bias states I, III and IV is discussed.