Transit-time oscillator with velocity-limited injection

The basic theory of a space-charge transit-time oscillator is outlined in which phase lag of current is caused by using low-velocity injection. Large negative resistances are anticipated at microwave frequencies, giving generation of moderate power levels with low-noise operation. Approximate design calculations for a representative idealised structure 100 ¿m square, based on silicon and operating at a frequency of 10 GHz, suggest a negative resistance of ¿50 ¿ and a negative Q factor of -¿/2, with a maximum output power of about 1 W and an efficiency of about 7%.