SiGe BJTs for low-voltage power applications

This paper describes the development of silicon germanium (SiGe) based transistors for low-voltage handset applications in the 0.9-2.4 GHz frequency range. The SiGe BJTs developed for this effort consisted of two types; the first were small-signal devices, the second were power devices with a modified collector for increased breakdown voltage. Small-signal devices, at V/sub c/=4.0 V, exhibited an f/sub T/=15 GHz and f/sub MAX/=14 GHz, with 15 dB MSG/MAG at 2 GHz. Load-pull results for these devices demonstrated a power gain G/sub p/=16 dB, P/sub 1dB/=18 dBm and PAE (P/sub 1/ /sub dB/)=29% if tuned for power and G/sub p/ 13.8 dB, P/sub 1/ /sub dB/=17 dBm and PAE(P/sub 1/ /sub dB/)=41%, if tuned for efficiency. When driven into compression, the devices achieved >50% PAE at an output power of 20 dBm and a gain of 8 dB. Power devices at V/sub c/=5.0 V showed G/sub p/=16 dB, P/sub 1dB/=25 dBm, PAE(P/sub 1/ /sub dB/)=52%.