Two separate Heterojunction Bipolar Transistor (HBT) PA blocks are fabricated onto an InGaP die; one supports the GSM850/900 bands, the other supports the DCS1800 and PCS1900 bands. ¡El InGaP PA die, the silicon MFC die, PHEMT switch die, and the passive components are mounted on a multi-layer laminate substrate. ¡El assembly is encapsulated with plastic overmold. ¡El FEM incorporates full support for a Serial Peripheral Interface (SPI) bus function. ¡El SPI controller shall accept SPI telegrams with data fields that support PA and switchplexer-related functions. All FEM operating modes and switch states shall be determined by the SPI telegram. ¡El Multi-function Control (MFC) provides for interoperation with a specified transceiver that will establish a closed loop power control mechanism. ¡El external circuit uses the Linear Detector output to set a fixed bias point for 8PSK (EDGE) mode and a variable bias point for GMSK (GSM) mode. ¡El power control loop together with the MFC will reduce sensitivity to antenna load, input drive, temperature, power supply, and process variation. ¡El combined circuit configures the PA for fixed gain in 8PSK mode while providing the ability to optimize the PA bias at different power levels to maximize efficiency.