EFFECT OF DIFFUSION OF ELECTRONS ON SMALL-SIGNAL IMPEDANCE OF A GUNN DIODE

Abstract

An expression for small-signal admittance of a Gunn diode has been achieved. The treatment includes especially the diffusion of electrons. The continuity and Poisson's equations have been solved without neglectthe diff-usion term In the equations. The v(E) and O(i) character-istics have been approximated by the equations deduced frorc eight point analysis of the latest available curves. This is in contrast with the earlier seven and three point analyses. The values of the .coefficients in the equations have been obtained by solving the eight simultaneous equations with the help of a computer IBM 1620. The expressions for conductance and susceptance derived from the admittance expression are complicated. Neglecting the less important terms the expressions have been simpli-fied to some extent. To examine the variation of the condu-ctance and the susceptance their values have been computed over a wide range of frequencies. The conductance is found to be negative at frequencies around the transit-time frequency of the electrons. This Is Sn complete agreement with the results reported by earlier researchers who did not consider the effect of the diffusion term. However, the magnitude of the negative resistance differs slightly from earlier ones. At higher frequencies the theories that ignore diffusion indicate the presence of oscillations with. slowly damping conductance. The diffusion effects strongly and increase the damping of the conductance. In both cases the conductanc