Maximizing the Frequency of Negative-Resistance Oscillation

High-frequency oscillation is often desired from a circuit consisting of a one-port negative-resistance element, e.g., a tunnel diode and a passive linear load. The designer must then choose a negative-resistance element capable of producing oscillation at the desired frequency. In this paper the question of frequency "capability" is investigated on the basis of the usual circuit model for a tunnel diode. Theoretical expressions for the maximum frequencies of quasi-harmonic oscillation with resistive loads and parallel-RC loads are derived. The method of analysis, utilizing impedance loci in the complex plane, leads logically to the discovery of loads that are superior to the parallel-RC load. Experimental data support the theoretical predictions.