A SiGe controlled-class power amplifier applied to reconfigurable mobile systems

An integrated two-stage reconfigurable power amplifier (PA) operating at 1.75 GHz for GSM1800 (DCS) and 1.95 GHz for UMTS/WCDMA is proposed. The PA uses 2.5 V supply voltage and was designed using 0.25 fun SiGe BiCMOS technology from ST Microelectronics. In order to fulfill both DCS and UMTS/W-CDMA requirements, especially on efficiency and linearity respectively, the amplifier is able to shift its two-stage classes of operation independently, by acting on bias circuits and tuning output network. To fulfill UMTS linearity requirement, PA operates in class A/AB mode with 27% PAE at the required 24 dBm output power whereas to fulfill DCS output power and efficiency requirements, PA operates in class AB/F mode with 49% PAE at the required 27 dBm output power and a maximum of 70% PAE is reached.