An RF transceiver having dual-mode envelope restoration architecture. In
narrow-band applications such as GSM/EDGE, a switch-mode amplifier is
used to provide an envelope signal for amplitude modulating the
phase-modulated signals. To achieve required modulation bandwidth in
wide-band applications such as WDCMA, an analog amplifier is used to
provide the envelope signal. Furthermore, in the wide-band mode, the
envelope modulation is applied through the base of an emitter follower
while the collector voltage is scaled to achieve a desired power output
in the amplitude-modulated signals.