A Doherty amplifier is able to enhance efficiency in low-power and high-power RF communication states by enabling carrier and peaking amplifiers as required, and controlling bias modulation, depending on traffic loading levels in each of a set of consecutive communications timeslots. For example, if, in a low-power state, traffic loading levels do not exceed a relatively lower threshold in a communications timeslot, carrier amplifiers are selectively enabled as needed, peaking amplifiers are not enabled, and carrier amplifier bias levels are kept substantially constant. If, in an intermediate-power state, the lower threshold is exceeded but a relatively higher threshold is not exceeded, all carrier amplifiers are enabled, peaking amplifiers are selectively enabled, and bias levels are kept substantially constant. If, in a high-power state, the higher threshold is exceeded, all carrier and peaking amplifiers can be enabled, and the peaking amplifier bias tracks the RF envelope of the received RF signal.