A computer simulation of a GaAs Gunn diode in a parallel resonant circuit has been made to determine the optimum device and circuit parameters. The maximum dc to RF efficiency, 5 to 8 percent, is obtained when the product of doping and length is between 10
12and 2 × 10
12cm
-2, the product of frequency and length is 10
7cm/s, and the bias voltage divided by length is 8000 V/cm for a load resistance of

where R
0is the low-voltage resistance of the diode. The product of output power and load resistance varies with frequency

as

where

is 12,000 watt-ohm-GHz
2for a load resistance of

. The frequency can be varied over an octave tuning range by the resonant circuit.