Natural frequencies of negative resistors with parasitics

The regions of allowed natural frequencies in Re p≥0 are determined for two different circuits which physically correspond to linearized equivalent circuits for tunnel diodes. One circuit consists of a parasitic resistance in series with the parallel capacity and negative resistance of a tunnel diode; the other contains series inductance. Passive networks to obtain any possible natural frequency are given. Multiple diode circuits are treated and for identical diodes it is shown that the best results occur with two diodes.