A WCDMA HBT power amplifier module with integrated Si DC power management IC for current reduction under backoff operation

This paper presents a WCDMA power amplifier (PA) module which integrates a GaAs HBT MMIC PA and a Si BiCMOS DC power management IC in a compact 3 x 5mm(2) package. The all-in-one approach is suitable for handset applications. A closed-loop controlled DC-DC buck converter allows the power management IC to adaptively optimize the PA collector voltage as a function of output power and thereby reduce current consumption under backoff operation. In addition, the IC contains a low dropout voltage regulator (LDO) which supplies an internally regulated voltage for the PA mirror bias with an enable function compatible with future baseband chipset control requirement. The PAM achieves excellent current reduction over a wide range of output power (Pout) up to 27.5dBm, while maintaining ACLR1 below -40dBc. At 16dBm and 24dBm Pout, the current consumptions are reduced from 162mA and 370mA, to 75mA and 257mA, respectively, compared to the PA with constant collector bias.