Improved Performance of High Voltage, Microwave Power, Static Induction Transistors

The performance of static induction transistors (SITs), fabricated with 10.5-μm pitch (gate-to-gate spacing) has been reported previously.[1] This presentation will discuss the improvements in performance that are achieved when the pitch is further reduced to 7 μm. These new SITs have demonstrated saturated cw output power levels of 11OWat 225 MHz with 6-dB power gain and 68% drain efficiency, and 25W at 900 MHz with 9-dB power gain and 54% drain efficiency. This performance level was achieved while operating the SIT test amplifier at dc supply voltage levels up to 90V. Small-signal measurements on these SITs indicate a unity power gain frequency, f
_MAG
, in X-band.