A transmitter includes a dual mode modulator and an amplifier coupled to
the dual mode modulator. The dual mode modulator implements a linear
modulation scheme during a first mode of the modulator to produce a
variable envelope modulated signal. The dual mode modulator implements a
non-linear modulation scheme during a second mode of the modulator to
produce a constant envelope modulated signal. The amplifier is biased as
a linear amplifier during the first mode of the modulator and is biased
as a non-linear amplifier during the second mode of the modulator. A
feed-forward connection between the dual mode modulator and the amplifier
is used to indicate a change in modulation mode and to adjust the bias of
the amplifier. A power of the constant envelope modulated signal is
increased such that an operating point of the amplifier remains
substantially constant during the first and second modes of the
modulator.