Lumped-circuit representation of Gunn diodes in domain mode

It is shown that the lumped circuit that has been used to date to represent a Gunn diode with a steadily propagating domain cannot and does not properly account for the transient, and therefore, high-frequency behavior of a Gunn diode. We have derived the nodal equations that must be obeyed by any circuit that is to represent a Gunn diode with a steadily propagating domain under all conditions --small signal and large signal, sinusoidal steady state, and transient. The validity of the new circuit and the fact that the conventional circuit would give erroneous results under transient conditions have been checked by transient experiments on the computer simulated Gunn diode. It is also shown that the domain differential capacitance is approximately half of what is given by zero diffusion theory, a result first predicted by Kuru, Robson, and Kino, and the discrepency is accounted for by the nonzero width of the accumulation layer, and incomplete depletion in the depletion layer.