Effect of Johnson noise on l.s.a. oscillators

The r.m.s. electron-density fluctuations (Johnson noise) within the GaAs of l.s.a. oscillators are shown to be about 10% of the mean density. The effect of these fluctuations is determined by an analytic calculation of l.s.a.-oscillator efficiency (similar to that of Bott and Hilsum, 1967). The specification of the velocity/field characteristic of conduction electrons in GaAs in an analytical form, which separates the importance of peak/valley ratio and negative differential mobility, permits an indication of the optimum form of the characteristic for the l.s.a. mode. The calculated efficiencies are somewhat smaller than those of previous calculations.