DOUBLE-DOPED POWER HJFETS FOR DIGITAL CELLULAR PHONES

This paper describes the 950 MHz power performance of double-doped AlG aAs/InGaAs/AlGaAs Heterojunction FETs (HJFETs) operated at a drain bia s voltage (V-ds) of 2.2 and 3.0 V for personal digital cellular phones . At V-ds = 3.0 V, a 17.5 mm gate width (W-g) HJFET with a maximum dra in current (I-max) of 500 mA/mm showed 1.4 W output power (P-out) and 50.0% power-added efficiency (PAE) with -50.3 dBc adjacent channel lea kage power at a 50 kHz off-carrier frequency (P-adj). While a 21.0 mm W-g HJFET with 600 mA/mm I-max demonstrated 1.86 W P-out and 62.8% PAE with -50.5 dBc P-adj at V-ds = 2.2 V. Harmonic balance simulation rev ealed that flat transconductance characteristics of the developed HJFE T with respect to gate bias voltage are effective in suppressing inter modulation distortion under large signal operation. A low effective kn ee voltage of the device also enables high P-out as well as high PAE e ven under reduced bias voltages.