LSA relaxation oscillator principles

Oversized n-GaAs diodes operating in the LSA mode with doping-to-frequency ratios in the 1-5×10⁵s/cm³range are investigated in circuits that contain a short-circuited high impedance transmission line foreshortened to resonate the electronic parallel capacitance of the diode. By comparing computer simulations with experiments, such diodes are shown to operate in a nonsinusoidal LSA relaxation mode which offers good efficiency, effective space-charge control, and a fast buildup of the oscillations; details of the computer program are also given. A simple analysis is developed which defines the inductive and capacitive time constants controlling the voltage waveshape and explains the frequency tuning with bias voltage and the effective space-charge control. The analysis is shown to be suitable for oscillator design purposes.